Alkaline Water Electrolysis for Efficient Hydrogen Production

Abstract

Hydrogen production from water electrolysis is a sustainable and environmentally benign strategy in comparison with fossil fuel-based hydrogen. However, this promising technique suffers from the high energy consumption and unsatisfactory cost due to the sluggish kinetics of both half reaction and inferior stability of electrocatalysts. To address this challenge, herein, we present a timely and comprehensive review on advances in alkaline water electrolysis that is already commercialized for large scale hydrogen production. The design principles and strategies with aiming to promote the performance of hydrogen generation are discussed from the view of electrocatalyst, electrode, reaction and system. The challenges and related prospects are presented at last, hopefully to provide essential ideas and to promote the wide application of hydrogen production.

Keywords

water electrolysis / hydrogen production / integrated electrode / coupled reaction

References

[1] Wang J, Gao Y, Kong H, Kim J, Choi S, Ciucci F, Hao Y, Yang S, Shao Z, Lim J. Non-precious-metal catalysts for alkaline water electrolysis: operando characterizations, theoretical calculations, and recent advances[J]. Chem. Soc. Rev., 2020, 49(24): 9154-9196.

[2] Xu L L, Ren D Y, Zhao X F, Yi Y. Janus-TiNbCO₂ for hydrogen evolution reaction with high conductivity and catalytic activity[J]. J. Electrochem., 2021, 27(5): 570-578.

[3] Huang C Q, Zhou J Q, Duan D S, Zhou Q C, Wang J M, Peng B W, Yu L, Yu Y. Roles of heteroatoms in electrocatalysts for alkaline water splitting: A review focusing on the reaction mechanism[J]. Chinese J. Catal., 2022, 43(8): 2091-2110.

[4] Boppella R, Tan J, Yang W, Moon J. Homologous CoP/NiCoP heterostructure on N-doped carbon for highly efficient and pH-universal hydrogen evolution electrocatalysis[J]. Adv. Funct. Mater., 2019, 29(6): 1807976.

[5] Cao X Y, Xia J F, Meng X, Xu J Y, Liu Q Y, Wang Z H. Stimuli-responsive DNA-gated nanoscale porous carbon derived from ZIF-8[J]. Adv. Funct. Mater., 2019, 29(34): 1902237.

[6] Wu Y P, Zhou W, Zhao J, Dong W W, Lan Y Q, Li D S, Sun C H, Bu X H. Surfactant-assisted phase-selective synthesis of new cobalt MOFs and their efficient electrocatalytic hydrogen evolution reaction[J]. Angew. Chem. Int. Ed., 2017, 56(42): 13001-13005.

[7] Tang C, Gan L F, Zhang R, Lu W B, Jiang X E, Asiri A M, Sun X P, Wang J, Chen L. Ternary Fe_xCo_1-xP nanowire array as a robust hydrogen evolution reaction electrocatalyst with Pt-like activity: experimental and theoretical insight[J]. Nano Lett., 2016, 16(10): 6617-6621.

[8] He Y M, Liu L R, Zhu C, Guo S S, Golani P, Koo B, Tang P Y, Zhao Z Q, Xu M Z, Yu P, Zhou X, Gao C T, Wang X W, Shi Z D, Zheng L, Yang J F, Shin B, Arbiol J, Duan H G, Du Y H, Heggen M, Dunin-Borkowski R E, Guo W L, Wang Q J, Zhang Z H, Liu Z. Amorphizing noble metal chalcogenide catalysts at the single-layer limit towards hydrogen production[J]. Nat. Catal., 2022, 5(3): 212-221.

[9] Zhang J Q, Zhao Y F, Guo X, Chen C, Dong C L, Liu R S, Han C P, Li Y D, Gogotsi Y, Wang G X. Single platinum atoms immobilized on an MXene as an efficient catalyst for the hydrogen evolution reaction[J]. Nat. Catal., 2018, 1(12): 985-992.

[10] Cao E P, Chen Z M, Wu H, Yu P, Wang Y, Xiao F, Chen S, Du S C, Xie Y, Wu Y Q, Ren Z Y. Boron-induced electronic-structure reformation of CoP nanoparticles drives enhanced pH-universal hydrogen evolution[J]. An-gew. Chem. Int. Ed., 2020, 59(10): 4154-4160.

[11] Xu J Y, Liu T F, Li J J, Li B, Liu Y F, Zhang B S, Xiong D H, Amorim I, Li W, Liu L F. Boosting the hydrogen evolution performance of ruthenium clusters through synergistic coupling with cobalt phosphide[J]. Energy Environ. Sci., 2018, 11(7): 1819-1827.

[12] Zheng Z L, Yu L, Gao M, Chen X Y, Zhou W, Ma C, Wu L H, Zhu J F, Meng X Y, Hu J T, Tu Y C, Wu S S, Mao J, Tian Z Q, Deng D H. Boosting hydrogen evolution on MoS₂ via co-confining selenium in surface and cobalt in inner layer[J]. Nat. Commun., 2020, 11(1): 3315.

[13] Liu W, Wang X T, Wang F, Du K F, Zhang Z F, Guo Y Z, Yin H Y, Wang D H. A durable and pH-universal self-standing MoC-Mo₂C heterojunction electrode for efficient hydrogen evolution reaction[J]. Nat. Commun., 2021, 12(1): 6776.

[14] Jiang K, Liu B Y, Luo M, Ning S C, Peng M, Zhao Y, Lu Y R, Chan T S, de Groot F M F, Tan Y W. Single platinum atoms embedded in nanoporous cobalt selenide as electrocatalyst for accelerating hydrogen evolution reaction[J]. Nat. Commun., 2019, 10(1): 1743.

[15] Zhang R, Wang X X, Yu S J, Wen T, Zhu X W, Yang F X, Sun X N, Wang X K, Hu W P. Ternary NiCo₂P_x nanowires as pH-universal electrocatalysts for highly efficient hydrogen evolution reaction[J]. Adv. Mater., 2017, 29(9): 1605502.

[16] Zhang X, Yu X L, Zhang L J, Zhou F, Liang Y Y, Wang R H. Molybdenum phosphide/carbon nanotube hybrids as pH-universal electrocatalysts for hydrogen evolution reaction[J]. Adv. Funct. Mater., 2018, 28(16): 1706523.

[17] Tian F Y, Geng S, He L, Huang Y R, Fauzi A, Yang W W, Liu Y Q, Yu Y S. Interface engineering: PSS-PPy wrapping amorphous Ni-Co-P for enhancing neutral-pH hydrogen evolution reaction performance[J]. Chem. Eng. J., 2021, 417: 129232.

[18] Gupta S, Patel N, Miotello A, Kothari D C. Cobalt-boride: an efficient and robust electrocatalyst for hydrogen evolution reaction[J]. J. Power Sources, 2015, 279: 620-625.

[19] Gao R, Dai Q B, Du F, Yan D P, Dai L M. C60-adsorbed single-walled carbon nanotubes as metal-free, pH-universal, and multifunctional catalysts for oxygen reduction, oxygen evolution, and hydrogen evolution[J]. J. Am. Chem. Soc., 2019, 141(29): 11658-11666.

[20] Yang M J, Zhang Y, Jian J H, Fang L, Li J, Fang Z S, Yuan Z K, Dai L M, Chen X D, Yu D S. Donor-acceptor nanocarbon ensembles to boost metal-free all-pH hydrogen evolution catalysis by combined surface and dual electronic modulation[J]. Angew. Chem. Int. Ed., 2019, 58(45): 16217-16222.

[21] Feng L L, Yu G T, Wu Y Y, Li G D, Li H, Sun Y H, Asefa T, Chen W, Zou X X. High-index faceted Ni₃S₂ nanosheet arrays as highly active and ultrastable electrocatalysts for water splitting[J]. J. Am. Chem. Soc., 2015, 137(44): 14023-14026.

[22] Cao D F, Sheng B B, Qi Z H, Xu W J, Chen S M, Moses O A, Long R, Xiong Y J, Wu X J, Song L. Self-optimizing iron phosphorus oxide for stable hydrogen evolution at high current[J]. Appl. Catal. B Environ., 2021, 298: 120559.

[23] Zhang S C, Wang W B, Hu F L, Mi Y, Wang S Z, Liu Y W, Ai X M, Fang J K, Li H Q, Zhai T Y. 2D CoOOH sheet-encapsulated Ni₂P into tubular arrays realizing 1000 mA·cm^-2-level-current-density hydrogen evolution over 100 h in neutral water[J]. Nano-Micro Lett., 2020, 12(1): 140.

[24] Xu Q C, Jiang H, Zhang H X, Hu Y J, Li C Z. Heterogeneous interface engineered atomic configuration on ultrathin Ni(OH)₂/Ni₃S₂ nanoforests for efficient water splitting[J]. Appl. Catal. B Environ., 2019, 242: 60-66.

[25] Liu Y, Yang Y P, Peng Z K, Liu Z Y, Chen Z M, Shang L, Lu S Y, Zhang T R. Self-crosslinking carbon dots loaded ruthenium dots as an efficient and super-stable hydrogen production electrocatalyst at all pH values[J]. Nano Energy, 2019, 65: 104023.

[26] Yang F N, Luo Y T, Yu Q M, Zhang Z Y, Zhang S, Liu Z B, Ren W C, Cheng H M, Li J, Liu B L. A durable and efficient electrocatalyst for saline water splitting with current density exceeding 2000 mA·cm^-2[J]. Adv. Funct. Mater., 2021, 31(21): 2010367.

[27] Nairan A, Liang C W, Chiang S W, Wu Y, Zou P C, Khan U, Liu W D, Kang F Y, Guo S J, Wu J B, Yang C. Proton selective adsorption on Pt-Ni nano-thorn array electrodes for superior hydrogen evolution activity[J]. Energy Environ. Sci., 2021, 14(3): 1594-1601.

[28] Wu L B, Zhang F H, Song S W, Ning M H, Zhu Q, Zhou J Q, Gao G H, Chen Z Y, Zhou Q C, Xing X X, Tong T, Yao Y, Bao J M, Yu L, Chen S, Ren Z F. Efficient alkaline water/seawater hydrogen evolution by a nanorod-nanoparticle-structured Ni-MoN catalyst with fast water-dissociation kinetics[J]. Adv. Mater., 2022, 34(21): 2201774.

[29] Wu X K, Wang Z C, Zhang D, Qin Y N, Wang M H, Han Y, Zhan T R, Yang B, Li S X, Lai J P, Wang L. Solvent-free microwave synthesis of ultra-small Ru-Mo₂C@CNT with strong metal-support interaction for industrial hydrogen evolution[J]. Nat. Commun., 2021, 12(1): 4018.

[30] Menezes P W, Indra A, Zaharieva I, Walter C, Loos S, Hoffmann S, Schlögl R, Dau H, Driess M. Helical cobalt borophosphates to master durable overall water-splitting[J]. Energy Environ. Sci., 2019, 12(3): 988-999.

[31] Qian G F, Chen J L, Yu T Q, Luo L, Yin S B. N-doped graphene-decorated NiCo alloy coupled with mesoporous NiCoMoO nano-sheet heterojunction for enhanced water electrolysis activity at high current density[J]. Nano-Micro Lett., 2021, 13(1): 77.

[32] Xie W F, Li Z H, Shao M F, Wei M. Layered double hydroxide-based core-shell nanoarrays for efficient electrochemical water splitting[J]. Front. Chem. Sci. Eng., 2018, 12(3): 537-554.

[33] Yu Z Y, Duan Y, Feng X Y, Yu X X, Gao M R, Yu S H. Clean and affordable hydrogen fuel from alkaline water splitting: past, recent progress, and future prospects[J]. Adv. Mater., 2021, 33(31): 2007100.

[34] Lagadec M F, Grimaud A. Water electrolysers with closed and open electrochemical systems[J]. Nat. Mater., 2020, 19(11): 1140-1150.

[35] Li M T, Zheng X Q, Li L, Wei Z D. Research progress of hydrogen oxidation and hydrogen evolution reaction mechanism in alkaline media[J]. Acta Phys. -Chim. Sin., 2021, 37(9): 2007054.

[36] Qin X P, Zhu S Q, Zhang L L, Sun S H, Shao M H. Theoretical studies of metal-N-C for oxygen reduction and hydrogen evolution reactions in acid and alkaline solutions[J]. J. Electrochem., 2021, 27(2): 185-194.

[37] Zhang S B, Wu Y F, Zhang Y X, Niu Z Q. Dual-atom catalysts: controllable synthesis and electrocatalytic applications[J]. Sci. China Chem., 2021, 64(11): 1908-1922.

[38] Norskov J K, Bligaard T, Logadottir A, Kitchin J R, Chen J G, Pandelov S, Norskov J K. Trends in the exchange current for hydrogen evolution[J]. J. Electrochem. Soc., 2005, 152(3): 23-26.

[39] Hinnemann B, Moses P G, Bonde J, Jörgensen K P, Nielsen J H, Horch S, Chorkendorff I, Nörskov J K. Biomimetic hydrogen evolution: MoS₂ nanoparticles as catalyst for hydrogen evolution[J]. J. Am. Chem. Soc., 2005, 127(15): 5308-5309.

[40] Jaramillo Thomas F, Jörgensen Kristina P, Bonde J, Nielsen Jane H, Horch S, Chorkendorff I. Identification of active edge sites for electrochemical H₂ evolution from MoS₂ nanocatalysts[J]. Science, 2007, 317(5834): 100-102.

[41] Zheng Y, Jiao Y, Zhu Y H, Li L H, Han Y, Chen Y, Du A J, Jaroniec M, Qiao S Z. Hydrogen evolution by a metal-free electrocatalyst[J]. Nat. Commun., 2014, 5(1): 3783.

[42] Tian J Q, Liu Q, Asiri A M, Sun X P. Self-supported nanoporous cobalt phosphide nanowire arrays: an efficient 3D hydrogen-evolving cathode over the wide range of pH 0-14[J]. J. Am. Chem. Soc., 2014, 136(21): 7587-7590.

[43] Chen Y J, Ji S F, Chen C, Peng Q, Wang D S, Li Y D. Single-atom catalysts: synthetic strategies and electrochemical applications[J]. Joule, 2018, 2(7): 1242-1264.

[44] Cheng N C, Stambula S, Wang D, Banis M N, Liu J, Riese A, Xiao B W, Li R Y, Sham T K, Liu L M, Botton G A, Sun X L. Platinum single-atom and cluster catalysis of the hydrogen evolution reaction[J]. Nat. Commun., 2016, 7(1): 13638.

[45] Li A L, Ooka H, Bonnet N, Hayashi T, Sun Y M, Jiang Q K, Li C, Han H X, Nakamura R. Stable potential windows for long-term electrocatalysis by manganese oxides under acidic conditions[J]. Angew. Chem. Int. Ed., 2019, 58(15): 5054-5058.

[46] Yang F N, Luo Y T, Yu Q M, Zhang Z Y, Zhang S, Liu Z B, Ren W C, Cheng H M, Li J, Liu B L. A durable and efficient electrocatalyst for saline water splitting with current density exceeding 2000 mA·cm^-2[J]. Adv. Funct. Mater., 2021, 31(21): 2010367.

[47] Kosmala T, Baby A, Lunardon M, Perilli D, Liu H, Durante C, Di Valentin C, Agnoli S, Granozzi G. Operando visualization of the hydrogen evolution reaction with atomic-scale precision at different metal-graphene interfaces[J]. Nat. Catal., 2021, 4(10): 850-859.

[48] Shao M F, Zhang R K, Li Z H, Wei M, Evans D G, Duan X. Layered double hydroxides toward electrochemical energy storage and conversion: design, synthesis and applications[J]. Chem. Commun., 2015, 51(88): 15880-15893.

[49] Li J M, Jiang S, Shao M F, Wei M. Host-guest engineering of layered double hydroxides towards efficient oxygen evolution reaction: recent advances and perspectives[J]. Catalysts, 2018, 8(5): 214.

[50] Wang D S. 2D materials modulating layered double hydroxides for electrocatalytic water splitting[J]. Chinese J Catal., 2022, 43(6): 1380-1398.

[51] Zhou L, Shao M F, Wei M, Duan X. Advances in efficient electrocatalysts based on layered double hydroxides and their derivatives[J]. J. Energy Chem., 2017, 26(6): 1094-1106.

[52] Zhang L H, Chuai H Y, Liu H, Fan Q, Kuang S Y, Zhang S, Ma X B. Facet dependent oxygen evolution activity of spinel cobalt oxides[J]. J. Electrochem., 2022, 28(2): 2108481.

[53] Liu Y K, Jiang S, Li S J, Zhou L, Li Z H, Li J M, Shao M F. Interface engineering of (Ni, Fe)S₂@MoS₂ heterostructures for synergetic electrochemical water splitting[J]. Appl. Catal. B Environ., 2019, 247: 107-114.

[54] Zhou L, Shao M F, Li J B, Jiang S, Wei M, Duan X. Two-dimensional ultrathin arrays of CoP: electronic modulation toward high performance overall water splitting[J]. Nano Energy, 2017, 41: 583-590.

[55] Li Z H, Shao M F, An H L, Wang Z X, Xu S M, Wei M, Evans D G, Duan X. Fast electrosynthesis of Fe-containing layered double hydroxide arrays toward highly efficient electrocatalytic oxidation reactions[J]. Chem. Sci., 2015, 6(11): 6624-6631.

[56] Li Z H, Shao M F, Zhou L, Zhang R K, Zhang C, Wei M, Evans D G, Duan X. Directed growth of metal-organic frameworks and their derived carbon-based network for efficient electrocatalytic oxygen reduction[J]. Adv. Mater., 2016, 28(12): 2337-2344.

[57] Song Y J, Li Z H, Fan K, Ren Z, Xie W F, Yang Y S, Shao M F, Wei M. Ultrathin layered double hydroxides nanosheets array towards efficient electrooxidation of 5-hydroxymethylfurfural coupled with hydrogen generation[J]. Appl. Catal. B Environ., 2021, 299: 120699.

[58] Gao R, Zhu J, Yan D P. Transition metal-based layered double hydroxides for photo(electro)chemical water splitting: a mini review[J]. Nanoscale, 2021, 13(32): 13593-13603.

[59] Zhou L, Jiang S, Liu Y K, Shao M F, Wei M, Duan X. Ultrathin CoNiP@layered double hydroxides core-shell nanosheets arrays for largely enhanced overall water splitting[J]. ACS Appl. Energy Mater., 2018, 1(2): 623-631.

[60] Li A, Zhang L, Wang F Z, Zhang L, Li L, Chen H M, Wei Z D. Rational design of porous Ni-Co-Fe ternary metal phosphides nanobricks as bifunctional electrocatalysts for efficient overall water splitting[J]. Appl. Catal. B Environ., 2022, 310: 121353.

[61] Wang Z J, Guo P, Cao S F, Chen H Y, Zhou S N, Liu H H, Wang H W, Zhang J B, Liu S Y, Wei S X, Sun D F, Lu X Q. Contemporaneous inverse manipulation of the valence configuration to preferred CO²⁺ and Ni³⁺ for enhanced overall water electrocatalysis[J]. Appl. Catal. B Environ., 2021, 284: 119725.

[62] Zhao Y, Gao Y X, Chen Z, Li Z J, Ma T Y, Wu Z X, Wang L. Trifle Pt coupled with NiFe hydroxide synthesized via corrosion engineering to boost the cleavage of water molecule for alkaline water-splitting[J]. Appl. Catal. B Environ., 2021, 297: 120395.

[63] Zhang L, Wang X Y, Li A, Zheng X Q, Peng L S, Huang J W, Deng Z H, Chen H M, Wei Z D. Rational construction of macroporous CoFeP triangular plate arrays from bimetal-organic frameworks as high-performance overall water-splitting catalysts[J]. J. Mater. Chem. A, 2019, 7(29): 17529-17535.

[64] Chen L, Wang Y P, Zhao X, Wang Y C, Li Q, Wang Q C, Tang Y G, Lei Y P. Trimetallic oxyhydroxides as active sites for large-current-density alkaline oxygen evolution and overall water splitting[J]. J. Mater. Sci. Technol., 2022, 110: 128-135.

[65] Liu H H, Yan Z H, Chen X, Li J H, Zhang L, Liu F M, Fan G L, Cheng F Y. Electrodeposition of Pt-decorated Ni(OH)₂/CeO₂ hybrid as superior bifunctional electrocatalyst for water splitting[J]. Research, 2020, 2020: 9068270.

[66] Xie W F, Song Y K, Li S J, Shao M F, Wei M. Integrated nanostructural electrodes based on layered double hydroxides[J]. Energy Environ. Mater., 2019, 2(3): 158-171.

[67] Xie W F, Li H, Cui G Q, Li J B, Song Y K, Li S J, Zhang X, Lee J Y, Shao M F, Wei M. NiSn atomic pair on an integrated electrode for synergistic electrocatalytic CO₂ reduction[J]. Angew. Chem. Int. Ed., 2021, 60(13): 7382-7388.

[68] Li J Z, Li H, Xie W F, Li S J, Song Y K, Fan K, Lee J Y, Shao M F. Flame-assisted synthesis of O-coordinated single-atom catalysts for efficient electrocatalytic oxygen reduction and hydrogen evolution reaction[J]. Small Methods, 2022, 6(1): 2101324.

[69] Li Z H, Cui J Y, Liu Y K, Li J B, Liu K, Shao M F. Electrosynthesis of well-defined metal-organic framework films and the carbon nanotube network derived from them toward electrocatalytic applications[J]. ACS Appl. Mater. Interfaces, 2018, 10(40): 34494-34501.

[70] Li S J, Xie W F, Song Y K, Shao M F. Layered double hydroxide@polydopamine core-shell nanosheet arrays-derived bifunctional electrocatalyst for efficient, flexible, all-solid-state zinc-air battery[J]. ACS Sustainable Chem. Eng., 2019, 8(1): 452-459.

[71] Song Y K, Xie W F, Shao M F. Recent advances in integrated electrode for electrocatalytic carbon dioxide reduction[J]. Acta Phys. -Chim. Sin., 2021, 38(6): 2101028.

[72] Li S J, Xie W F, Song Y K, Li Y, Song Y J, Li J Z, Shao M F. Integrated CoPt electrocatalyst combined with upgrading anodic reaction to boost hydrogen evolution reaction[J]. Chem. Eng. J., 2022, 437: 135473.

[73] Phillips R, Dunnill C W. Zero gap alkaline electrolysis cell design for renewable energy storage as hydrogen gas[J]. RSC Adv., 2016, 6(102): 100643-100651.

[74] Haug P, Kreitz B, Koj M, Turek T. Process modelling of an alkaline water electrolyzer[J]. Int. J. Hydrog. Energy, 2017, 42(24): 15689-15707.

[75] Song Y J, Ji K Y, Duan H H, Shao M F. Hydrogen production coupled with water and organic oxidation based on layered double hydroxides[J]. Exploration, 2021, 1(3): 210050.

[76] Li Y, Wei X F, Chen L S, Shi J L. Electrocatalytic hydrogen production trilogy[J]. Angew. Chem. Int. Ed., 2021, 60(36): 19550-19571.

[77] Tang C, Zheng Y, Jaroniec M, Qiao S Z. Electrocatalytic refinery for sustainable production of fuels and chemicals[J]. Angew. Chem. Int. Ed., 2021, 60(36): 19572-19590.

[78] Lu Y X, Liu T Y, Dong C L, Huang Y C, Li Y F, Chen J, Zou Y Q, Wang S Y. Tuning the selective adsorption site of biomass on Co₃O₄ by Ir single atoms for electrosynthesis[J]. Adv. Mater., 2021, 33(8): e2007056.

[79] Song Y J, Jiang S, He Y H, Wu Y, Wan X, Xie W, Wang J J, Li Z H, Duan H B, Shao M F. Metal vacancy-enriched layered double hydroxide for biomass molecule electrooxidation coupled with hydrogen production[J]. Fundam. Res., 2022: DOI: 10.1016/j.fmre.2022.1005.1023.

[80] Song Y K, Xie W F, Song Y J, Li H, Li S J, Jiang S, Lee J Y, Shao M F. Bifunctional integrated electrode for high-efficient hydrogen production coupled with 5-hydroxymethylfurfural oxidation[J]. Appl. Catal. B Environ., 2022, 312: 121400.

[81] Li Z H, Yan Y F, Xu S M, Zhou H, Xu M, Ma L N, Shao M F, Kong X G, Wang B, Zheng L R, Duan H H. Alcohols electrooxidation coupled with H₂ production at high current densities promoted by a cooperative catalyst[J]. Nat. Commun., 2022, 13(1): 147.

[82] Zhou H, Li Z H, Xu S M, Lu L L, Xu M, Ji K Y, Ge R X, Yan Y F, Ma L N, Kong X G, Zheng L R, Duan H H. Selectively upgrading lignin derivatives to carboxylates through electrochemical oxidative C(OH)-C bond cleavage by a Mn-doped cobalt oxyhydroxide catalyst[J]. Angew. Chem. Int. Ed., 2021, 60(16): 8976-8982.

[83] Li X, Zhao L L, Yu J Y, Liu X Y, Zhang X L, Liu H, Zhou W J. Water splitting: from electrode to green energy system[J]. Nano-Micro Lett., 2020, 12(1): 131.

[84] Chi J, Yu H M. Water electrolysis based on renewable energy for hydrogen production[J]. Chinese J. Catal., 2018, 39(3): 390-394.

[85] Wang Y, Sharma A, Duong T, Arandiyan H, Zhao T W, Zhang D D, Su Z, Garbrecht M, Beck F J, Karuturi S, Zhao C, Catchpole K. Direct solar hydrogen generation at 20% efficiency using low-cost materials[J]. Adv. Energy Mater., 2021, 11(34): 2101053.

[86] Liang J, Han X, Qiu Y X, Fang Q Y, Zhang B Y, Wang W P, Zhang J, Ajayan P M, Lou J. A low-cost and high-efficiency integrated device toward solar-driven water splitting[J]. ACS Nano, 2020, 14(5): 5426-5434.

[87] Wang L M, Zhang L L, Ma W, Wan H, Zhang X J, Zhang X, Jiang S Y, Zheng J Y, Zhou Z. In situ anchoring massive isolated Pt atoms at cationic vacancies of α-Ni_xFe_1-x(OH)₂ to regulate the electronic structure for overall water splitting[J]. Adv. Funct. Mater., 2022: 2203342.

[88] Luo J S, Im J H, Mayer M T, Schreier M, Nazeeruddin M K, Park N G, Tilley S D, Fan H J, Gratzel M. Water photolysis at 12.3% efficiency via perovskite photovoltaics and Earth-abundant catalysts[J]. Science, 2014, 345(6204): 1593-1596.

[89] Fu H C, Varadhan P, Lin C H, He J H. Spontaneous solar water splitting with decoupling of light absorption and electrocatalysis using silicon back-buried junction[J]. Nat. Commun., 2020, 11(1): 3930.

[90] Sharma A, Duong T, Liu P, Soo J Z, Yan D, Zhang D D, Riaz A, Samundsett C, Shen H P, Yang C, Karuturi S K, Catchpole K, Beck F J. Direct solar to hydrogen conversion enabled by silicon photocathodes with carrier selective passivated contacts[J]. Sustain. Energ. Fuels, 2022, 6(2): 349-360.

[91] Park H, Park I J, Lee M G, Kwon K C, Hong S P, Kim D H, Lee S A, Lee T H, Kim C, Moon C W, Son D Y, Jung G H, Yang H S, Lee J R, Lee J, Park N G, Kim S Y, Kim J Y, Jang H W. Water splitting exceeding 17% solar-to-hydrogen conversion efficiency using solution-processed Ni-based electrocatalysts and perovskite/Si tandem solar cell[J]. ACS Appl. Mater. Interfaces, 2019, 11(37): 33835-33843.

[92] Karuturi S K, Shen H P, Sharma A, Beck F J, Varadhan P, Duong T, Narangari P R, Zhang D D, Wan Y M, He J H, Tan H H, Jagadish C, Catchpole K. Over 17% efficiency stand-alone solar water splitting enabled by perovskite-silicon tandem absorbers[J]. Adv. Energy Mater., 2020, 10(28): 2000772.

[93] Gao J, Sahli F, Liu C J, Ren D, Guo X Y, Werner J, Jeangros Q, Zakeeruddin S M, Ballif C, Gratzel M, Luo J S. Solar water splitting with perovskite/silicon tandem cell and TiC-supported Pt nanocluster electrocatalyst[J]. Joule, 2019, 3(12): 2930-2941.

[94] Sun P L, Zhou Y T, Li H Y, Zhang H, Feng L G, Cao Q E, Liu S X, Wagberg T, Hu G Z. Round-the-clock bifunctional honeycomb-like nitrogen-doped carbon-decorated Co₂P/Mo₂C-heterojunction electrocatalyst for direct water splitting with 18.1% STH efficiency[J]. Appl. Catal. B Environ., 2022, 310: 121354.

[95] Zhao L L, Yang Z Y, Cao Q, Yang L J, Zhang X F, Jia J, Sang Y H, Wu H J, Zhou W J, Liu H. An earth-abundant and multifunctional Ni nanosheets array as electrocatalysts and heat absorption layer integrated thermoelectric device for overall water splitting[J]. Nano Energy, 2019, 56: 563-570.

[96] Zhang Y, Kumar S, Marken F, Krasny M, Roake E, Eslava S, Dunn S, Da Como E, Bowen C R. Pyro-electrolytic water splitting for hydrogen generation[J]. Nano Energy, 2019, 58: 183-191.

[97] Ren X H, Fan H Q, Wang C, Ma J W, Li H, Zhang M C, Lei S H, Wang W J. Wind energy harvester based on coaxial rotatory freestanding triboelectric nanogenerators for self-powered water splitting[J]. Nano Energy, 2018, 50: 562-570.

[98] Tang W, Han Y, Han C B, Gao C Z, Cao X, Wang Z L. Self-powered water splitting using flowing kinetic energy[J]. Adv. Mater., 2015, 27(2): 272-276.