1. School of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, China; Photocatalysis International Research Center, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan 2. Photocatalysis International Research Center, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
Photocatalysts have attracted great research interest owing to their excellent properties and potential for simultaneously addressing challenges related to energy needs and environmental pollution. Photocatalytic particles need to be in contact with their respective media to exhibit efficient photocatalytic performances. However, it is difficult to separate nanometer-sized photocatalytic materials from reaction media later, which may lead to secondary pollution and a poor recycling performance. Hydrogel photocatalysts with a three-dimensional (3D) network structures are promising support materials for photocatalysts based on features such as high specific surface areas and adsorption capacities and good environmental compatibility. In this review, hydrogel photocatalysts are classified into two different categories depending on their elemental composition and recent progresses in the methods for preparing hydrogel photocatalysts are summarized. Moreover, current applications of hydrogel photocatalysts in energy conversion and environmental remediation are reviewed. Furthermore, a comprehensive outlook and highlight future challenges in the development of hydrogel photocatalysts are presented.
S E Hosseini, M A Wahid. Hydrogen from solar energy, a clean energy carrier from a sustainable source of energy. International Journal of Energy Research, 2020, 44(6): 4110–4131 https://doi.org/10.1002/er.4930
6
Y Zhang, J Ren, Y Pu, et al. Solar energy potential assessment: a framework to integrate geographic, technological, and economic indices for a potential analysis. Renewable Energy, 2020, 149: 577–586 https://doi.org/10.1016/j.renene.2019.12.071
7
J Gong, C Li, M R Wasielewski. Advances in solar energy conversion. Chemical Society Reviews, 2019, 48(7): 1862–1864 https://doi.org/10.1039/C9CS90020A
Q Wang, T Hisatomi, Q Jia, et al. Scalable water splitting on particulate photocatalyst sheets with a solar-to-hydrogen energy conversion efficiency exceeding 1%. Nature Materials, 2016, 15(6): 611–615 https://doi.org/10.1038/nmat4589
10
W J Ong, L L Tan, Y H Ng, et al. Graphitic carbon nitride (g-C3N4)-based photocatalysts for artificial photosynthesis and environmental remediation: are we a step closer to achieving sustainability? Chemical Reviews, 2016, 116(12): 7159–7329 https://doi.org/10.1021/acs.chemrev.6b00075
11
J Luo, S Zhang, M Sun, et al. A critical review on energy conversion and environmental remediation of photocatalysts with remodeling crystal lattice, surface, and interface. ACS Nano, 2019, 13(9): 9811–9840 https://doi.org/10.1021/acsnano.9b03649
12
B Tian, B Tian, B Smith, et al. Supported black phosphorus nanosheets as hydrogen-evolving photocatalyst achieving 5.4% energy conversion efficiency at 353 K. Nature Communications, 2018, 9(1): 1397 https://doi.org/10.1038/s41467-018-03737-4
13
P Zhang, X W D Lou. Design of heterostructured hollow photocatalysts for solar-to-chemical energy conversion. Advanced Materials, 2019, 31(29): 1900281 https://doi.org/10.1002/adma.201900281
14
P Dhiman, M Naushad, K M Batoo, et al. Nano FexZn1−xO as a tuneable and efficient photocatalyst for solar powered degradation of bisphenol A from aqueous environment. Journal of Cleaner Production, 2017, 165: 1542–1556 https://doi.org/10.1016/j.jclepro.2017.07.245
15
X Tang, Z Huang, Y Cao, et al. Mo promotes interfacial interaction and induces oxygen vacancies in 2D/2D of Mo-g-C3N4 and Bi2O2CO3 photocatalyst for enhanced NO oxidation. Industrial & Engineering Chemistry Research, 2020, 59(20): 9509–9518 https://doi.org/10.1021/acs.iecr.0c00777
16
J Yi, J Liao, K Xia, et al. Integrating the merits of two-dimensional structure and heteroatom modification into semiconductor photocatalyst to boost NO removal. Chemical Engineering Journal, 2019, 370: 944–951 https://doi.org/10.1016/j.cej.2019.03.182
17
A Fujishima, K Honda. Electrochemical photolysis of water at a semiconductor electrode. Nature, 1972, 238(5358): 37–38 https://doi.org/10.1038/238037a0
18
W Zhou, W Li, J Wang, et al. Ordered mesoporous black TiO2 as highly efficient hydrogen evolution photocatalyst. Journal of the American Chemical Society, 2014, 136(26): 9280–9283 https://doi.org/10.1021/ja504802q
19
Y Hu. A highly efficient photocatalyst—hydrogenated black TiO2 for the photocatalytic splitting of water. Angewandte Chemie International Edition, 2012, 51(50): 12410–12412 https://doi.org/10.1002/anie.201206375
20
A Naldoni, M Altomare, G Zoppellaro, et al. Photocatalysis with reduced TiO2: from black TiO2 to cocatalyst-free hydrogen production. ACS Catalysis, 2019, 9(1): 345–364 https://doi.org/10.1021/acscatal.8b04068
21
N Liu, V Häublein, X Zhou, et al. “Black” TiO2 nanotubes formed by high-energy proton implantation show noble-metal-co-catalyst free photocatalytic H2-evolution. Nano Letters, 2015, 15(10): 6815–6820 https://doi.org/10.1021/acs.nanolett.5b02663
22
C C Hsu, N L Wu. Synthesis and photocatalytic activity of ZnO/ZnO2 composite. Journal of Photochemistry and Photobiology A Chemistry, 2005, 172(3): 269–274 https://doi.org/10.1016/j.jphotochem.2004.12.014
23
E S Elmolla, M Chaudhuri. Degradation of amoxicillin, ampicillin and cloxacillin antibiotics in aqueous solution by the UV/ZnO photocatalytic process. Journal of Hazardous Materials, 2010, 173(1–3): 445–449 https://doi.org/10.1016/j.jhazmat.2009.08.104
24
W Yu, J Zhang, T Peng. New insight into the enhanced photocatalytic activity of N-, C- and S-doped ZnO photocatalysts. Applied Catalysis B: Environmental, 2016, 181: 220–227 https://doi.org/10.1016/j.apcatb.2015.07.031
25
C Tian, Q Zhang, A Wu, et al. Cost-effective large-scale synthesis of ZnO photocatalyst with excellent performance for dye photodegradation. Chemical Communications, 2012, 48(23): 2858–2860 https://doi.org/10.1039/c2cc16434e
26
J Fu, J Yu, C Jiang, et al. g-C3N4-based heterostructured photocatalysts. Advanced Energy Materials, 2018, 8(3): 1701503 https://doi.org/10.1002/aenm.201701503
L Ye, J Liu, Z Jiang, et al. Facets coupling of BiOBr-g-C3N4 composite photocatalyst for enhanced visible-light-driven photocatalytic activity. Applied Catalysis B: Environmental, 2013, 142–143: 1–7 https://doi.org/10.1016/j.apcatb.2013.04.058
29
Y Li, R He, P Han, et al. A new concept: volume photocatalysis for efficient H2 generation—using low polymeric carbon nitride as an example. Applied Catalysis B: Environmental, 2020, 279: 119379 https://doi.org/10.1016/j.apcatb.2020.119379
30
M Xu, L Han, S Dong. Facile fabrication of highly efficient g-C3N4/Ag2O heterostructured photocatalysts with enhanced visible-light photocatalytic activity. ACS Applied Materials & Interfaces, 2013, 5(23): 12533–12540 https://doi.org/10.1021/am4038307
31
H Kato, A Kudo. Visible-light-response and photocatalytic activities of TiO2 and SrTiO3 photocatalysts codoped with antimony and chromium. Journal of Physical Chemistry B, 2002, 106(19): 5029–5034 https://doi.org/10.1021/jp0255482
32
K Domen, A Kudo, T Onishi. Mechanism of photocatalytic decomposition of water into H2 and O2 over NiOSrTiO3. Journal of Catalysis, 1986, 102(1): 92–98 https://doi.org/10.1016/0021-9517(86)90143-0
33
K Iwashina, A Kudo. Rh-doped SrTiO3 photocatalyst electrode showing cathodic photocurrent for water splitting under visible-light irradiation. Journal of the American Chemical Society, 2011, 133(34): 13272–13275 https://doi.org/10.1021/ja2050315
34
T Takata, J Jiang, Y Sakata, et al. Photocatalytic water splitting with a quantum efficiency of almost unity. Nature, 2020, 581(7809): 411–414 https://doi.org/10.1038/s41586-020-2278-9
35
C Xu, P Ravi Anusuyadevi, C Aymonier, et al. Nanostructured materials for photocatalysis. Chemical Society Reviews, 2019, 48(14): 3868–3902 https://doi.org/10.1039/C9CS00102F
36
Z Wei, Y Zhu, W Guo, et al. Enhanced twisting degree assisted overall water splitting on a novel nano-dodecahedron BiVO4-based heterojunction. Applied Catalysis B: Environmental, 2020, 266: 118664 https://doi.org/10.1016/j.apcatb.2020.118664
37
Z Jiang, Z Huang, W Guo, et al. Photocatalytic overall water splitting on isolated semiconductor photocatalyst sites in an ordered mesoporous silica matrix: a multiscale strategy. Journal of Catalysis, 2019, 370: 210–223 https://doi.org/10.1016/j.jcat.2018.12.020
38
W Fang, Z Jiang, L Yu, et al. Novel dodecahedron BiVO4:YVO4 solid solution with enhanced charge separation on adjacent exposed facets for highly efficient overall water splitting. Journal of Catalysis, 2017, 352: 155–159 https://doi.org/10.1016/j.jcat.2017.04.030
39
Y Li, P Han, Y Hou, et al. Oriented ZnmIn2Sm+3@In2S3 heterojunction with hierarchical structure for efficient photocatalytic hydrogen evolution. Applied Catalysis B: Environmental, 2019, 244: 604–611 https://doi.org/10.1016/j.apcatb.2018.11.088
40
Y Li, Y Hou, Q Fu, et al. Oriented growth of ZnIn2S4/In(OH)3 heterojunction by a facile hydrothermal transformation for efficient photocatalytic H2 production. Applied Catalysis B: Environmental, 2017, 206: 726–733 https://doi.org/10.1016/j.apcatb.2017.01.062
41
A Meng, L Zhang, B Cheng, et al. Dual cocatalysts in TiO2 photocatalysis. Advanced Materials, 2019, 31(30): 1807660 https://doi.org/10.1002/adma.201807660
42
J Ran, J Zhang, J Yu, et al. Earth-abundant cocatalysts for semiconductor-based photocatalytic water splitting. Chemical Society Reviews, 2014, 43(22): 7787–7812 https://doi.org/10.1039/C3CS60425J
43
Q Wang, K Domen. Particulate photocatalysts for light-driven water splitting: mechanisms, challenges, and design strategies. Chemical Reviews, 2020, 120(2): 919–985 https://doi.org/10.1021/acs.chemrev.9b00201
44
K Nakata, A Fujishima. TiO2 photocatalysis: design and applications. Journal of Photochemistry and Photobiology C, Photochemistry Reviews, 2012, 13(3): 169–189 https://doi.org/10.1016/j.jphotochemrev.2012.06.001
45
H Chen, S W Lee, T H Kim, et al. Photocatalytic decomposition of benzene with plasma sprayed TiO2-based coatings on foamed aluminum. Journal of the European Ceramic Society, 2006, 26(12): 2231–2239 https://doi.org/10.1016/j.jeurceramsoc.2005.04.024
46
J Shang, W Li, Y Zhu. Structure and photocatalytic characteristics of TiO2 film photocatalyst coated on stainless steel webnet. Journal of Molecular Catalysis A Chemical, 2003, 202(1–2): 187–195 https://doi.org/10.1016/S1381-1169(03)00200-0
47
J O Carneiro, V Teixeira, A Portinha, et al. Iron-doped photocatalytic TiO2 sputtered coatings on plastics for self-cleaning applications. Materials Science and Engineering B, 2007, 138(2): 144–150 https://doi.org/10.1016/j.mseb.2005.08.130
48
X Liu, Q Chen, L Lv, et al. Preparation of transparent PVA/TiO2 nanocomposite films with enhanced visible-light photocatalytic activity. Catalysis Communications, 2015, 58: 30–33 https://doi.org/10.1016/j.catcom.2014.08.032
49
R Zhang, M Ma, Q Zhang, et al. Multifunctional g-C3N4/graphene oxide wrapped sponge monoliths as highly efficient adsorbent and photocatalyst. Applied Catalysis B: Environmental, 2018, 235: 17–25 https://doi.org/10.1016/j.apcatb.2018.04.061
50
W Jiang, W Luo, R Zong, et al. Polyaniline/carbon nitride nanosheets composite hydrogel: a separation-free and high-efficient photocatalyst with 3D hierarchical structure. Small, 2016, 12(32): 4370–4378 https://doi.org/10.1002/smll.201601546
51
Z Zhang, F Xiao, Y Guo, et al. One-pot self-assembled three-dimensional TiO2-graphene hydrogel with improved adsorption capacities and photocatalytic and electrochemical activities. ACS Applied Materials & Interfaces, 2013, 5(6): 2227–2233 https://doi.org/10.1021/am303299r
52
N X D Mai, J Bae, I T Kim, et al. A recyclable, recoverable, and reformable hydrogel-based smart photocatalyst. Environmental Science: Nano, 2017, 4(4): 955–966 https://doi.org/10.1039/C6EN00695G
53
J S Im, B C Bai, S J In, et al. Improved photodegradation properties and kinetic models of a solar-light-responsive photocatalyst when incorporated into electrospun hydrogel fibers. Journal of Colloid and Interface Science, 2010, 346(1): 216–221 https://doi.org/10.1016/j.jcis.2010.02.043
54
L Lei, W Wang, C Wang, et al. Hydrogel-supported graphitic carbon nitride nanosheets loaded with Pt atoms as a novel self-water-storage photocatalyst for H2 evolution. Journal of Materials Chemistry A, Materials for Energy and Sustainability, 2020, 8(45): 23812–23819 https://doi.org/10.1039/D0TA07805K
55
W Lei, S Qi, Q Rong, et al. Diffusion-freezing-induced microphase separation for constructing large-area multiscale structures on hydrogel surfaces. Advanced Materials, 2019, 31(32): 1808217 https://doi.org/10.1002/adma.201808217
56
Q Xiang, J Yu, M Jaroniec. Graphene-based semiconductor photocatalysts. Chemical Society Reviews, 2012, 41(2): 782–796 https://doi.org/10.1039/C1CS15172J
57
A Mills, S Le Hunte. An overview of semiconductor photocatalysis. Journal of Photochemistry and Photobiology A Chemistry, 1997, 108(1): 1–35 https://doi.org/10.1016/S1010-6030(97)00118-4
58
K Maeda. Z-scheme water splitting using two different semiconductor photocatalysts. ACS Catalysis, 2013, 3(7): 1486–1503 https://doi.org/10.1021/cs4002089
59
H Wang, L Zhang, Z Chen, et al. Semiconductor heterojunction photocatalysts: design, construction, and photocatalytic performances. Chemical Society Reviews, 2014, 43(15): 5234–5244 https://doi.org/10.1039/C4CS00126E
60
G Liu, J C Yu, G Q Lu, et al. Crystal facet engineering of semiconductor photocatalysts: motivations, advances and unique properties. Chemical Communications, 2011, 47(24): 6763–6783 https://doi.org/10.1039/c1cc10665a
61
L Jing, Y Qu, B Wang, et al. Review of photoluminescence performance of nano-sized semiconductor materials and its relationships with photocatalytic activity. Solar Energy Materials and Solar Cells, 2006, 90(12): 1773–1787 https://doi.org/10.1016/j.solmat.2005.11.007
62
R Abe, K Sayama, H Sugihara. Development of new photocatalytic water splitting into H2 and O2 using two different semiconductor photocatalysts and a shuttle redox mediator IO3−/I−. Journal of Physical Chemistry B, 2005, 109(33): 16052–16061 https://doi.org/10.1021/jp052848l
63
F Chen, W An, L Liu, et al. Highly efficient removal of bisphenol A by a three-dimensional graphene hydrogel—AgBr@rGO exhibiting adsorption/photocatalysis synergy. Applied Catalysis B: Environmental, 2017, 217: 65–80 https://doi.org/10.1016/j.apcatb.2017.05.078
64
C Liu, M Yue, L Liu, et al. A separation-free 3D network ZnO/rGO-rGH hydrogel: adsorption enriched photocatalysis for environmental applications. RSC Advances, 2018, 8(40): 22402–22410 https://doi.org/10.1039/C8RA03873B
65
J Yun, D Jin, Y S Lee, et al. Photocatalytic treatment of acidic waste water by electrospun composite nanofibers of pH-sensitive hydrogel and TiO2. Materials Letters, 2010, 64(22): 2431–2434 https://doi.org/10.1016/j.matlet.2010.08.001
66
G Sharma, A Kumar, S Sharma, et al. Fabrication and characterization of novel Fe0@Guar gum-crosslinked-soya lecithin nanocomposite hydrogel for photocatalytic degradation of methyl violet dye. Separation and Purification Technology, 2019, 211: 895–908 https://doi.org/10.1016/j.seppur.2018.10.028
67
M Thomas, G A Naikoo, M U D Sheikh, et al. Effective photocatalytic degradation of Congo red dye using alginate/carboxymethyl cellulose/TiO2 nanocomposite hydrogel under direct sunlight irradiation. Journal of Photochemistry and Photobiology A Chemistry, 2016, 327: 33–43 https://doi.org/10.1016/j.jphotochem.2016.05.005
68
W Jiang, Y Liu, J Wang, et al. Separation-free polyaniline/TiO2 3D hydrogel with high photocatalytic activity. Advanced Materials Interfaces, 2016, 3(3): 1500502 https://doi.org/10.1002/admi.201500502
69
Y Chen, Z Xiang, D Wang, et al. Effective photocatalytic degradation and physical adsorption of methylene blue using cellulose/GO/TiO2 hydrogels. RSC Advances, 2020, 10(40): 23936–23943 https://doi.org/10.1039/D0RA04509H
70
X Chen, Q Chen, W Jiang, et al. Separation-free TiO2-graphene hydrogel with 3D network structure for efficient photoelectrocatalytic mineralization. Applied Catalysis B: Environmental, 2017, 211: 106–113 https://doi.org/10.1016/j.apcatb.2017.03.061
71
F Chen, W An, Y Li, et al. Fabricating 3D porous PANI/TiO2-graphene hydrogel for the enhanced UV-light photocatalytic degradation of BPA. Applied Surface Science, 2018, 427: 123–132 https://doi.org/10.1016/j.apsusc.2017.08.146
72
C Hou, Q Zhang, Y Li, et al. P25-graphene hydrogels: room-temperature synthesis and application for removal of methylene blue from aqueous solution. Journal of Hazardous Materials, 2012, 205–206: 229–235 https://doi.org/10.1016/j.jhazmat.2011.12.071
73
R Jiang, H Zhu, J Yao, et al. Chitosan hydrogel films as a template for mild biosynthesis of CdS quantum dots with highly efficient photocatalytic activity. Applied Surface Science, 2012, 258(8): 3513–3518 https://doi.org/10.1016/j.apsusc.2011.11.105
74
K Kaur, R Jindal. Comparative study on the behaviour of Chitosan-Gelatin based Hydrogel and nanocomposite ion exchanger synthesized under microwave conditions towards photocatalytic removal of cationic dyes. Carbohydrate Polymers, 2019, 207: 398–410 https://doi.org/10.1016/j.carbpol.2018.12.002
75
J Yang, J Gao, X Wang, et al. Polyacrylamide hydrogel as a template in situ synthesis of CdS nanoparticles with high photocatalytic activity and photostability. Journal of Nanoparticle Research, 2017, 19(10): 350 https://doi.org/10.1007/s11051-017-4048-7
76
H Zhu, Z Li, J Yang. A novel composite hydrogel for adsorption and photocatalytic degradation of bisphenol A by visible light irradiation. Chemical Engineering Journal, 2018, 334: 1679–1690 https://doi.org/10.1016/j.cej.2017.11.148
77
J Yang, D Chen, Y Zhu, et al. 3D–3D porous Bi2WO6/graphene hydrogel composite with excellent synergistic effect of adsorption-enrichment and photocatalytic degradation. Applied Catalysis B: Environmental, 2017, 205: 228–237 https://doi.org/10.1016/j.apcatb.2016.12.035
78
K Hashimoto, H Irie, A Fujishima. TiO2 photocatalysis: a historical overview and future prospects. Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 2005, 44(12): 8269–8285 https://doi.org/10.1143/JJAP.44.8269
J Schneider, M Matsuoka, M Takeuchi, et al. Understanding TiO2 photocatalysis: mechanisms and materials. Chemical Reviews, 2014, 114(19): 9919–9986 https://doi.org/10.1021/cr5001892
81
Q Guo, C Zhou, Z Ma, et al. Fundamentals of TiO2 photocatalysis: concepts, mechanisms, and challenges. Advanced Materials: Deerfield Beach, Fla, 2019, 31(50): 1901997 https://doi.org/10.1002/adma.201901997
Y Jiang, H Ning, C Tian, et al. Single-crystal TiO2 nanorods assembly for efficient and stable cocatalyst-free photocatalytic hydrogen evolution. Applied Catalysis B: Environmental, 2018, 229: 1–7 https://doi.org/10.1016/j.apcatb.2018.01.079
84
W Zhang, H He, Y Tian, et al. Synthesis of uniform ordered mesoporous TiO2 microspheres with controllable phase junctions for efficient solar water splitting. Chemical Science (Cambridge), 2019, 10(6): 1664–1670 https://doi.org/10.1039/C8SC04155E
85
J Hu, J Xie, W Jia, et al. Interesting molecule adsorption strategy induced energy band tuning: boosts 43 times photocatalytic water splitting ability for commercial TiO2. Applied Catalysis B: Environmental, 2020, 268: 118753 https://doi.org/10.1016/j.apcatb.2020.118753
86
X Li, J Shi, H Hao, et al. Visible light-induced selective oxidation of alcohols with air by dye-sensitized TiO2 photocatalysis. Applied Catalysis B: Environmental, 2018, 232: 260–267 https://doi.org/10.1016/j.apcatb.2018.03.043
87
R Qian, H Zong, J Schneider, et al. Charge carrier trapping, recombination and transfer during TiO2 photocatalysis: an overview. Catalysis Today, 2019, 335: 78–90 https://doi.org/10.1016/j.cattod.2018.10.053
88
Y Yue, X Wang, Q Wu, et al. Highly recyclable and super-tough hydrogel mediated by dual-functional TiO2 nanoparticles toward efficient photodegradation of organic water pollutants. Journal of Colloid and Interface Science, 2020, 564: 99–112 https://doi.org/10.1016/j.jcis.2019.12.069
89
D Arikal, A Kallingal. Photocatalytic degradation of azo and anthraquinone dye using TiO2/MgO nanocomposite immobilized chitosan hydrogels. Environmental Technology, 2019, online, doi:10.1080/09593330.2019.1701094 https://doi.org/10.1080/09593330.2019.1701094
90
M Lučić, N Milosavljević, M Radetić, et al. The potential application of TiO2/hydrogel nanocomposite for removal of various textile azo dyes. Separation and Purification Technology, 2014, 122: 206–216 https://doi.org/10.1016/j.seppur.2013.11.002
91
K Zhao, L Feng, H Lin, et al. Adsorption and photocatalytic degradation of methyl orange imprinted composite membranes using TiO2/calcium alginate hydrogel as matrix. Catalysis Today, 2014, 236: 127–134 https://doi.org/10.1016/j.cattod.2014.03.041
92
M Liu, Y Ishida, Y Ebina, et al. Photolatently modulable hydrogels using unilamellar titania nanosheets as photocatalytic crosslinkers. Nature Communications, 2013, 4(1): 2029 https://doi.org/10.1038/ncomms3029
93
J Liu, H Chen, X Shi, et al. Hydrogel microcapsules with photocatalytic nanoparticles for removal of organic pollutants. Environmental Science: Nano, 2020, 7(2): 656–664 https://doi.org/10.1039/C9EN01108K
94
S Khan, Y Kubota, W Lei, et al. One-pot synthesis of (anatase/bronze-type)-TiO2/carbon dot polymorphic structures and their photocatalytic activity for H2 generation. Applied Surface Science, 2020, 526: 146650 https://doi.org/10.1016/j.apsusc.2020.146650
95
Q Wu, F Huang, M Zhao, et al. Ultra-small yellow defective TiO2 nanoparticles for co-catalyst free photocatalytic hydrogen production. Nano Energy, 2016, 24: 63–71 https://doi.org/10.1016/j.nanoen.2016.04.004
96
M K Nowotny, L R Sheppard, T Bak, et al. Defect chemistry of titanium dioxide. Application of defect engineering in processing of TiO2-based photocatalysts. Journal of Physical Chemistry C, 2008, 112(14): 5275–5300 https://doi.org/10.1021/jp077275m
97
O Elbanna, M Zhu, M Fujitsuka, et al. Black phosphorus sensitized TiO2 mesocrystal photocatalyst for hydrogen evolution with visible and near-infrared light irradiation. ACS Catalysis, 2019, 9(4): 3618–3626 https://doi.org/10.1021/acscatal.8b05081
98
R Su, S Ge, H Li, et al. Synchronous synthesis of Cu2O/Cu/rGO@carbon nanomaterials photocatalysts via the sodium alginate hydrogel template method for visible light photocatalytic degradation. Science of the Total Environment, 2019, 693: 133657 https://doi.org/10.1016/j.scitotenv.2019.133657
99
J Wang, X Li, Q Cheng, et al. Construction of β-FeOOH@tunicate cellulose nanocomposite hydrogels and their highly efficient photocatalytic properties. Carbohydrate Polymers, 2020, 229: 115470 https://doi.org/10.1016/j.carbpol.2019.115470
100
Y Ding, Y Zhou, W Nie, et al. MoS2-GO nanocomposites synthesized via a hydrothermal hydrogel method for solar light photocatalytic degradation of methylene blue. Applied Surface Science, 2015, 357: 1606–1612 https://doi.org/10.1016/j.apsusc.2015.10.030
101
C Mu, Y Zhang, W Cui, et al. Removal of bisphenol A over a separation free 3D Ag3PO4-graphene hydrogel via an adsorption-photocatalysis synergy. Applied Catalysis B: Environmental, 2017, 212: 41–49 https://doi.org/10.1016/j.apcatb.2017.04.018
102
L Qin, R Ru, J Mao, et al. Assembly of MOFs/polymer hydrogel derived Fe3O4-CuO@hollow carbon spheres for photochemical oxidation: freezing replacement for structural adjustment. Applied Catalysis B: Environmental, 2020, 269: 118754 https://doi.org/10.1016/j.apcatb.2020.118754
103
M T Taghizadeh, V de Siyahi, H Ashassi-Sorkhabi, et al. ZnO, AgCl and AgCl/ZnO nanocomposites incorporated chitosan in the form of hydrogel beads for photocatalytic degradation of MB, E. coli and S. aureus. International Journal of Biological Macromolecules, 2020, 147: 1018–1028 https://doi.org/10.1016/j.ijbiomac.2019.10.070
104
S Chen, D L Jacobs, J Xu, et al. 1D nanofiber composites of perylene diimides for visible-light-driven hydrogen evolution from water. RSC Advances, 2014, 4(89): 48486–48491 https://doi.org/10.1039/C4RA09258A
105
S Chen, Y Li, C Wang. Visible-light-driven photocatalytic H2 evolution from aqueous suspensions of perylene diimide dye-sensitized Pt/TiO2 catalysts. RSC Advances, 2015, 5(21): 15880–15885 https://doi.org/10.1039/C4RA16245E
106
S Chen, C Wang, B R Bunes, et al. Enhancement of visible-light-driven photocatalytic H2 evolution from water over g-C3N4 through combination with perylene diimide aggregates. Applied Catalysis A, General, 2015, 498: 63–68 https://doi.org/10.1016/j.apcata.2015.03.026
107
S Yang, Y Gong, J Zhang, et al. Exfoliated graphitic carbon nitride nanosheets as efficient catalysts for hydrogen evolution under visible light. Advanced Materials, 2013, 25(17): 2452–2456 https://doi.org/10.1002/adma.201204453
108
Y Wang, X Wang, M Antonietti. Polymeric graphitic carbon nitride as a heterogeneous organocatalyst: from photochemistry to multipurpose catalysis to sustainable chemistry. Angewandte Chemie International Edition, 2012, 51(1): 68–89 https://doi.org/10.1002/anie.201101182
109
X Wang, K Maeda, X Chen, et al. Polymer semiconductors for artificial photosynthesis: hydrogen evolution by mesoporous graphitic carbon nitride with visible light. Journal of the American Chemical Society, 2009, 131(5): 1680–1681 https://doi.org/10.1021/ja809307s
110
X Wang, K Maeda, A Thomas, et al. A metal-free polymeric photocatalyst for hydrogen production from water under visible light. Nature Materials, 2009, 8(1): 76–80 https://doi.org/10.1038/nmat2317
111
C Hu, Y Lin, H C Yang. Recent developments in graphitic carbon nitride based hydrogels as photocatalysts. ChemSusChem, 2019, 12(9): 1769–1806 https://doi.org/10.1002/cssc.201901066
112
W Jiang, Y Zhu, G Zhu, et al. Three-dimensional photocatalysts with a network structure. Journal of Materials Chemistry A, Materials for Energy and Sustainability, 2017, 5(12): 5661–5679 https://doi.org/10.1039/C7TA00398F
113
J Li, X Yu, Y Zhu, et al. 3D–2D-3D BiOI/porous g-C3N4/graphene hydrogel composite photocatalyst with synergy of adsorption-photocatalysis in static and flow systems. Journal of Alloys and Compounds, 2021, 850: 156778 https://doi.org/10.1016/j.jallcom.2020.156778
114
Y C Chu, T J Lin, Y Lin, et al. Influence of P, S, O-doping on g-C3N4 for hydrogel formation and photocatalysis: an experimental and theoretical study. Carbon, 2020, 169: 338–348 https://doi.org/10.1016/j.carbon.2020.07.053
115
Y Liang, X Wang, W An, et al. Ag-C3N4@ppy-rGO 3D structure hydrogel for efficient photocatalysis. Applied Surface Science, 2019, 466: 666–672 https://doi.org/10.1016/j.apsusc.2018.10.059
116
J Hu, P Zhang, J Cui, et al. High-efficiency removal of phenol and coking wastewater via photocatalysis-Fenton synergy over a Fe-g-C3N4 graphene hydrogel 3D structure. Journal of Industrial and Engineering Chemistry, 2020, 84: 305–314 https://doi.org/10.1016/j.jiec.2020.01.012
117
G Liu, T Li, X Song, et al. Thermally driven characteristic and highly photocatalytic activity based on N-isopropyl acrylamide/high-substituted hydroxypropyl cellulose/g-C3N4 hydrogel by electron beam pre-radiation method. Journal of Thermoplastic Composite Materials, 2020, online, doi:10.1177/0892705-720944214 https://doi.org/10.1177/0892705720944214
118
G Zhang, Z Lan, X Wang. Conjugated polymers: catalysts for photocatalytic hydrogen evolution. Angewandte Chemie International Edition, 2016, 55(51): 15712–15727 https://doi.org/10.1002/anie.201607375
119
X Wang, L Chen, S Y Chong, et al. Sulfone-containing covalent organic frameworks for photocatalytic hydrogen evolution from water. Nature Chemistry, 2018, 10(12): 1180–1189 https://doi.org/10.1038/s41557-018-0141-5
120
D Liu, J Wang, X Bai, et al. Self-assembled PDINH supramolecular system for photocatalysis under visible light. Advanced Materials: Deerfield Beach, Fla, 2016, 28(33): 7284–7290 https://doi.org/10.1002/adma.201601168
121
E Cohen, H Weissman, I Pinkas, et al. Controlled self-assembly of photofunctional supramolecular nanotubes. ACS Nano, 2018, 12(1): 317–326 https://doi.org/10.1021/acsnano.7b06376
122
S Chen, P Slattum, C Wang, et al. Self-assembly of perylene imide molecules into 1D nanostructures: methods, morphologies, and applications. Chemical Reviews, 2015, 115(21): 11967–11998 https://doi.org/10.1021/acs.chemrev.5b00312
P Singh, L S Mittal, V Vanita, et al. Self-assembled vesicle and rod-like aggregates of functionalized perylene diimide: reaction-based near-IR intracellular fluorescent probe for selective detection of palladium. Journal of Materials Chemistry B, Materials for Biology and Medicine, 2016, 4(21): 3750–3759 https://doi.org/10.1039/C6TB00512H
125
Z Zhang, X Chen, H Zhang, et al. A highly crystalline perylene imide polymer with the robust built-in electric field for efficient photocatalytic water oxidation. Advanced Materials, 2020, 32(32): 1907746 https://doi.org/10.1002/adma.201907746
126
A S Weingarten, R V Kazantsev, L C Palmer, et al. Supramolecular packing controls H2 photocatalysis in chromophore amphiphile hydrogels. Journal of the American Chemical Society, 2015, 137(48): 15241–15246 https://doi.org/10.1021/jacs.5b10027
127
A S Weingarten, R V Kazantsev, L C Palmer, et al. Self-assembling hydrogel scaffolds for photocatalytic hydrogen production. Nature Chemistry, 2014, 6(11): 964–970 https://doi.org/10.1038/nchem.2075
128
H Sai, A Erbas, A Dannenhoffer, et al. Chromophore amphiphile-polyelectrolyte hybrid hydrogels for photocatalytic hydrogen production. Journal of Materials Chemistry A, Materials for Energy and Sustainability, 2020, 8(1): 158–168 https://doi.org/10.1039/C9TA08974H
129
J Byun, K Landfester, K Zhang. Conjugated polymer hydrogel photocatalysts with expandable photoactive sites in water. Chemistry of Materials, 2019, 31(9): 3381–3387 https://doi.org/10.1021/acs.chemmater.9b00544
130
F Li, J Yang, J Gao, et al. Enhanced photocatalytic hydrogen production of CdS embedded in cationic hydrogel. International Journal of Hydrogen Energy, 2020, 45(3): 1969–1980 https://doi.org/10.1016/j.ijhydene.2019.11.140
131
A L Luna, F Matter, M Schreck, et al. Monolithic metal-containing TiO2 aerogels assembled from crystalline pre-formed nanoparticles as efficient photocatalysts for H2 generation. Applied Catalysis B: Environmental, 2020, 267: 118660 https://doi.org/10.1016/j.apcatb.2020.118660
132
Z Jiang, X Zhang, G Yang, et al. Hydrogel as a miniature hydrogen production reactor to enhance photocatalytic hydrogen evolution activities of CdS and ZnS quantum dots derived from modified gel crystal growth method. Chemical Engineering Journal, 2019, 373: 814–820 https://doi.org/10.1016/j.cej.2019.05.112
133
J Yu, J Low, W Xiao, et al. Enhanced photocatalytic CO2-reduction activity of anatase TiO2 by coexposed {001} and {101} facets. Journal of the American Chemical Society, 2014, 136(25): 8839–8842 https://doi.org/10.1021/ja5044787
134
S N Habisreutinger, L Schmidt-Mende, J K Stolarczyk. Photocatalytic reduction of CO2 on TiO2 and other semiconductors. Angewandte Chemie International Edition, 2013, 52(29): 7372–7408 https://doi.org/10.1002/anie.201207199
135
J Ran, M Jaroniec, S Qiao. Cocatalysts in semiconductor-based photocatalytic CO2 reduction: achievements, challenges, and opportunities. Advanced Materials, 2018, 30(7): 1704649 https://doi.org/10.1002/adma.201704649
136
C Bie, B Zhu, F Xu, et al. In situ grown monolayer N-doped graphene on CdS hollow spheres with seamless contact for photocatalytic CO2 reduction. Advanced Materials, 2019, 31(42): 1902868 https://doi.org/10.1002/adma.201902868
H Jung, K M Cho, K H Kim, et al. Highly efficient and stable CO2 reduction photocatalyst with a hierarchical structure of mesoporous TiO2 on 3D graphene with few-layered MoS2. ACS Sustainable Chemistry & Engineering, 2018, 6(5): 5718–5724 https://doi.org/10.1021/acssuschemeng.8b00002
139
F Rechberger, M Niederberger. Translucent nanoparticle-based aerogel monoliths as 3-dimensional photocatalysts for the selective photoreduction of CO2 to methanol in a continuous flow reactor. Materials Horizons, 2017, 4(6): 1115–1121 https://doi.org/10.1039/C7MH00423K
140
C B Godiya, L A Martins Ruotolo, W Cai. Functional biobased hydrogels for the removal of aqueous hazardous pollutants: current status, challenges, and future perspectives. Journal of Materials Chemistry A, Materials for Energy and Sustainability, 2020, 8(41): 21585–21612 https://doi.org/10.1039/D0TA07028A
141
G Jing, L Wang, H Yu, et al. Recent progress on study of hybrid hydrogels for water treatment. Colloids and Surfaces A, Physicochemical and Engineering Aspects, 2013, 416: 86–94 https://doi.org/10.1016/j.colsurfa.2012.09.043
142
P Mohammadzadeh Pakdel, S J Peighambardoust. A review on acrylic based hydrogels and their applications in wastewater treatment. Journal of Environmental Management, 2018, 217: 123–143 https://doi.org/10.1016/j.jenvman.2018.03.076
143
M Zhang, W Luo, Z Wei, et al. Separation free C3N4/SiO2 hybrid hydrogels as high active photocatalysts for TOC removal. Applied Catalysis B: Environmental, 2016, 194: 105–110 https://doi.org/10.1016/j.apcatb.2016.04.049
144
M Zhang, W Jiang, D Liu, et al. Photodegradation of phenol via C3N4-agar hybrid hydrogel 3D photocatalysts with free separation. Applied Catalysis B: Environmental, 2016, 183: 263–268 https://doi.org/10.1016/j.apcatb.2015.10.049
145
J Yang, Z Li, H Zhu. Adsorption and photocatalytic degradation of sulfamethoxazole by a novel composite hydrogel with visible light irradiation. Applied Catalysis B: Environmental, 2017, 217: 603–614 https://doi.org/10.1016/j.apcatb.2017.06.029
146
M Hua, S Zhang, B Pan, et al. Heavy metal removal from water/wastewater by nanosized metal oxides: a review. Journal of Hazardous Materials, 2012, 211–212: 317–331 https://doi.org/10.1016/j.jhazmat.2011.10.016
M B Tahir, H Kiran, T Iqbal. The detoxification of heavy metals from aqueous environment using nano-photocatalysis approach: a review. Environmental Science and Pollution Research International, 2019, 26(11): 10515–10528 https://doi.org/10.1007/s11356-019-04547-x
149
Y Li, W Cui, L Liu, et al. Removal of Cr(VI) by 3D TiO2-graphene hydrogel via adsorption enriched with photocatalytic reduction. Applied Catalysis B: Environmental, 2016, 199: 412–423 https://doi.org/10.1016/j.apcatb.2016.06.053
150
Y Guo, J Bae, Z Fang, et al. Hydrogels and hydrogel-derived materials for energy and water sustainability. Chemical Reviews, 2020, 120(15): 7642–7707 https://doi.org/10.1021/acs.chemrev.0c00345
151
X Zhou, Y Guo, F Zhao, et al. Hydrogels as an emerging material platform for solar water purification. Accounts of Chemical Research, 2019, 52(11): 3244–3253 https://doi.org/10.1021/acs.accounts.9b00455
152
X Zhou, F Zhao, Y Guo, et al. Architecting highly hydratable polymer networks to tune the water state for solar water purification. Science Advances, 2019, 5(6): eaaw5484 https://doi.org/10.1126/sciadv.aaw5484
153
F Zhao, X Zhou, Y Shi, et al. Highly efficient solar vapour generation via hierarchically nanostructured gels. Nature Nanotechnology, 2018, 13(6): 489–495 https://doi.org/10.1038/s41565-018-0097-z
154
W Lei, S Khan, L Chen, et al. Hierarchical structures hydrogel evaporator and superhydrophilic water collect device for efficient solar steam evaporation. Nano Research, 2021, 14(4): 1135–1140 https://doi.org/10.1007/s12274-020-3162-5
155
M Gao, C K Peh, L Zhu, et al. Photothermal catalytic gel featuring spectral and thermal management for parallel freshwater and hydrogen production. Advanced Energy Materials, 2020, 10(23): 2000925 https://doi.org/10.1002/aenm.202000925
156
M Yang, C Tan, W Lu, et al. Spectrum tailored defective 2D semiconductor nanosheets aerogel for full-spectrum-driven photothermal water evaporation and photochemical degradation. Advanced Functional Materials, 2020, 30(43): 2004460 https://doi.org/10.1002/adfm.202004460