Recent progress and perspectives on Sb_(2)Se_(3)-based photocathodes for solar hydrogen production via photoelectrochemical water splitting

Photoelectrochemical(PEC) cells involved with semiconductor electrodes can simultaneously absorb solar energy and perform chemical reactions, which are considered as an attractive strategy to produce renewable and clean hydrogen energy. Sb_(2)Se_(3) has been widely investigated in constructing PEC photocathodes benefitting of its low toxicity, suitable band gap, superior optoelectronic properties, and outstanding photocorrosion stability. We first present a brief overview of basic concepts and principles of PEC water splitting as well as a comparison between Sb_(2)Se_(3) and other numerous candidates. Then the material characteristics and preparation methods of Sb_(2)Se_(3) are introduced. The development of Sb_(2)Se_(3)-based photocathodes in PEC water splitting with various architectures and engineering efforts(i.e., absorber engineering, interfaces engineering, co-catalyst engineering and tandem engineering) to improve solar-to-hydrogen(STH) efficiency are highlighted. Finally, we debate the possible future directions to further explore the researching fields of Sb_(2)Se_(3)-based photocathodes with a strongly positive outlook in PEC processed solar hydrogen production.

Nickel-coated silicon photocathode for water splitting in alkaline electrolytes

切开的 Photoelectrochemical (PEC ) 水是一条有希望的途径收获并且存储太阳能[1 ] 。硅广泛地由于它匹配太阳的光谱的合适的乐队差距(1.12 eV ) 为 PEC photoelectrodes 被调查了[2 ] 。这里，我们调查作为催化剂两个都采用镍并且第一次在基本电解质为 photoelectrochemical 氢进化保护 p 类型硅光阴极的层。硅光阴极被在 5 nm Ni 跟随的 p 类型硅晶片上扔 15 nm Ti 做。光阴极在碱的答案(1 M KOH ) 负担得起 0.3 V 对可逆的氢电极(RHE ) 的一个发作潜力。Ni/Ti/p-Si 光阴极的稳定性在 KOH 在 12 h 上看了 100 mV 腐烂，但是稳定性显著地被改进光阴极什么时候在钾硼酸盐缓冲区答案被操作(pH 9.5 ) 。电极表面被发现在 10 妈 / 厘米的经常的当前的密度在连续操作的 12 h 以后仍然保持未经触动 < 啜 class= “ a-plus-plus ” > 在钾硼酸盐缓冲区的 2 ，建议 Ni 负担得起 Si 的好保护在硼酸盐缓冲区基于光阴极。

Recent Advancements in Photoelectrochemical Water Splitting for Hydrogen Production

Sunlight is the most abundant and inexhaustible energy source on earth.However,its low energy density,dispersibility and intermittent nature make its direct utilization with industrial relevance challenging,suggesting that converting sunlight into chemical energy and storing it is a valuable measure to achieve global sustainable development.Carbon–neutral,clean and secondary pollution-free solar-driven water splitting to produce hydrogen is one of the most attractive avenues among all the current options and is expected to realize the transformation from dependence on fossil fuels to zero-pollution hydrogen.Artificial photosynthetic systems(APSs)based on photoelectrochemical(PEC)devices appear to be an ideal avenue to efficiently achieve solar-to-hydrogen conversion.In this review,we comprehensively highlight the recent developments in photocathodes,including architectures,semiconductor photoabsorbers and performance optimization strategies.In particular,frontier research cases of organic semiconductors,dye sensitization and surface grafted molecular catalysts applied to APSs based on frontier(molecular)orbital theory and semiconductor energy band theory are discussed.Moreover,research advances in typical photoelectrodes with the metal–insulator–semiconductor(MIS)architecture based on quantum tunnelling are also introduced.Finally,we discuss the benchmarks and protocols for designing integrated tandem photoelectrodes and PEC systems that conform to the solar spectrum to achieve high-efficiency and cost-effective solar-to-hydrogen conversion at an industrial scale in the near future.

Direct Synthesis of Molybdenum Phosphide Nanorods on Silicon Using Graphene at the Heterointerface for Efficient Photoelectrochemical Water Reduction

Transition metal phosphides(TMPs)and transition metal dichalcogenides(TMDs)have been widely investigated as photoelectrochemical(PEC)catalysts for hydrogen evolution reaction(HER).Using high-temperature processes to get crystallized compounds with large-area uniformity,it is still challenging to directly synthesize these catalysts on silicon photocathodes due to chemical incompatibility at the heterointerface.Here,a graphene interlayer is applied between p-Si and MoP nanorods to enable fully engineered interfaces without forming a metallic secondary compound that absorbs a parasitic light and provides an inefficient electron path for hydrogen evolution.Furthermore,the graphene facilitates the photogenerated electrons to rapidly transfer by creating Mo-O-C covalent bondings and energetically favorable band bending.With a bridging role of graphene,numerous active sites and anti-reflectance of MoP nanorods lead to significantly improved PEC-HER performance with a high photocurrent density of 21.8 mA cm−2 at 0 V versus RHE and high stability.Besides,low dependence on pH and temperature is observed with MoP nanorods incorporated photocathodes,which is desirable for practical use as a part of PEC cells.These results indicate that the direct synthesis of TMPs and TMDs enabled by graphene interlayer is a new promising way to fabricate Si-based photocathodes with high-quality interfaces and superior HER performance.

High performance n^+p-Si/Ti/NiS_xO_y photocathode for photoelectrochemical hydrogen evolution in alkaline solution

Silicon, as a promising semiconductor for fabricating photocathode toward photoelectrochemical hydrogen evolution reaction(PEC-HER), should be improved in light harvesting ability and catalytic kinetics to obtain high PEC performance. Herein, a novel amorphous Nickel Oxysulfide(NiS_xO_y) film is effectively integrated with a Ti protected n^+p-Si micropyramid photocathode by the electrodeposition method. The fabricated n^+p-Si/Ti/Ni SxOyphotocathode exhibits excellent PEC-HER performance with an onset potential of 0.5 V(at J =-0.1 mA/cm^2), a photocurrent density of-26 mA/cm^2 at 0 V vs. RHE, and long term stability of six hours in alkaline solution(pH ≈ 14). The synergy of unique n^+p-Si micropyramid architectures(omnidirectional broadband light harvesting ability), novel amorphous NiS_xO_y catalyst(high HER electrocatalytic activity and good optical transparency) results in the high performance of n^+pSi/Ti/Ni S_xO_y. This work offers a novel strategy for effectively integrating electrocatalysts with semiconductor to design efficient photoelectrode toward PEC water splitting.

Bismuth based photoelectrodes for solar water splitting

Photoelectrochemical water splitting is a sustainable path to generate valuable hydrogen using sunlight and water as the only inputs.Despite significant efforts to date,it is still a challenge to achieve photoelectrode with superior performance and long-term stability.Many bismuth-based semiconductor materials have demonstrated excellent visible light harvesting capability and suitable band edge for water splitting.Herein,we summarized the latest studies conducted on bismuth-based photoelectrodes for photoelectrochemical water splitting.Specifically,photoelectrochemical properties of copper bismuth oxide(CuBi_(2)O_(4)),bismuth ferrites(BiFeO_(3),Bi_(2)Fe_(4)O_(9)),bismuth vanadate(BiVO_(4)),bismuth tungstate(Bi_(2)WO_(6)),bismuth molybdate(Bi_(2)MoO_(6))and bismuth oxyhalids(BiOX,X=I,Cl,Br)are presented.Strategies to achieve high stability and photolectrochemical performance were discussed in the aspects of nanostructure formation,heterostructure assembly,practical defect engineering,preferential facet growth and oxygen evolution catalyst incorporation.

Triggering heteroatomic interdiffusion in one-pot-oxidation synthesized NiO/CuFeO_(2) heterojunction photocathodes for efficient solar hydrogen production from water splitting

Delafossite CuFeO_(2) is a promising photocathode material for cost-efficiently photoelectrochemical(PEC)water splitting,but the unfavorable conductivity and fast recombination dynamics of photogenerated carriers limit its PEC activity for water reduction.Here,we developed a heterostructure photocathode consisting of the Cu-doped NiO(Cu:NiO)hole selective layer(HSL)and Ni-doped CuFeO_(2)(Ni:CuFeO_(2))active layer by simply annealing a homogeneous Cu-Fe oxalate layer grown on the Ni film deposited on the fluorine doped tin oxide(FTO)substrate.The obtained heterostructure of Cu:NiO/Ni:CuFeO_(2) with enhanced charge carrier transportability and high-quality interface greatly promotes the separation of photogenerated carriers.Accordingly,the Cu:NiO/Ni:CuFeO_(2) photocathode exhibits a high photocurrent density of~0.9 mA·cm^(-2 )at 0.2 V(vs.reversible hydrogen electrode,RHE),outperforming most of the reported bare CuFeO_(2) photocathodes in the literature.And the photocurrent density can be further improved to 1.2 mA·cm^(-2) after decorating NiSx cocatalyst.

Si光阳极稳定性提高策略研究进展

利用光电化学水分解技术实现绿氢制取是解决人类面临的能源危机和环境污染的极有效与可行的途径之一,受到广泛的关注与研究。半导体Si作为一种优异的光电极材料,具有理想的1.12 eV窄带隙、宽太阳光谱吸收范围(300~1100 nm)、高的载流子传输性能(晶体硅μn=1350 cm^(2)/(V·s),μp=500 cm^(2)/(V·s),常温)以及高结晶性等优点。但是,Si的价带边远低于水分解析氧反应1.23 VRHE,以及析氧反应涉及四电子转移过程,导致Si光阳极本征析氧反应动力学缓慢;同时,Si光阳极表面会生成绝缘性SiO_(2)层或SiO_(2)(OH)^(2-)层,导致严重的光腐蚀和稳定性问题等,成为限制其实际应用的重大挑战。近年来,研究者提出了许多提高Si光阳极光氢转换效率与稳定性的策略。本文重点对Si光阳极的提高策略研究进展进行综述,包括催化层、保护层、电解液保护以及界面工程四类;其次对光电化学水分解基本原理以及Si半导体材料作光阳极的可行性与优缺点进行分析;最后基于上述研究进展,对提高Si光阳极效率与稳定性的未来发展进行了综述与展望。

CdS quantum dot sensitized p-type NiO as photocathode with integrated cobaloxime in photoelectrochemical cell for water splitting

CdS sensitized NiO electrode was used as the photoactive cathode in a photoelectrochemical cell for water splitting,avoiding the use of a sacrificial electron donor.Photocurrent increment under visible light irradiation was observed after integration of[Co（dmgH）_2（4-Me-py）Cl]（1） to the photocathode,suggesting 1 could accept electrons from photoexcited CdS for water reduction and NiO could move the holes in the valence band of CdS to anode for water oxidation.

Cu_(2)O/CeO_(2)异质结的制备与光电化学性能研究

通过电化学法在铜片表面生长Cu(OH)_(2)纳米线阵列,在氮气氛围下将其进行退火处理得到Cu_(2)O纳米线阵列,然后采用电沉积法在电极上沉积Cu_(2)O阻挡层和CeO_(2),制备得到Cu_(2)O/CeO_(2)异质结光阴极材料。利于扫描电子显微镜(SEM)、X-射线衍射(XRD)和X-射线光电子能谱(XPS)对材料的形貌和化学成分等进行表征,紫外-可见吸收光谱(UV-Vis)、线性扫描伏安法(LSV)和莫特肖特基曲线(M-S)等测试对其光电化学性能进行分析。实验数据结果表明,在0 V、RHE(可逆氢电极)下,Cu_(2)O/CeO_(2)光阴极的光电流密度达到-6.55 mA/cm^(2),相比仅Cu_(2)O的光电流密度(-3.67 mA/cm^(2))提升了1.78倍。随后,通过ALD(原子层沉积)制备TiO_(2)作为保护层,负载Pt作为析氢反应(HER)的助催化剂。最终Cu_(2)O/CeO_(2)/TiO_(2)/Pt光阴极的光电流密度达到-10.9 mA/cm^(2)(0 V vs.RHE),应用偏压光子-电流效率(ABPE)达2.02%。实验的研究成果对Cu_(2)O基光阴极材料在光电化学水分解领域的广泛应用具有重要意义。

碳化硅纳米线阵列基一体化光电阳极用于高效裂解水制氢

近年来,光电催化裂解水制氢已经发展成为获取氢能最重要的途径之一.然而,半导体材料固有的较低的光吸收效率和较高的载流子复合率成为限制其发展的主要障碍.以N掺杂4H-SiC单晶片为原料,通过阳极氧化法制备了N掺杂4H-SiC纳米线阵列基一体化光电阳极,聚焦于优化阳极析氧反应条件,在光照和外加电场的共同作用下成功实现了高效裂解水制氢.相比于块体,碳化硅纳米线阵列基一体化光电阳极的裂解水制氢性能表现出了显著的提升.以Ag/AgCl电极为参比电极,开启电压从1.224 V降低至-0.021 V,1.4 V电压下的电流密度从2.64 mA·cm^(-2)提升至3.61 mA·cm^(-2).通过构建具有纳米结构的半导体光电阳极,可以有效提高其光吸收能力并优化其电荷转移路径,从而显著提升光电催化裂解水制氢的效率.

CdTe/CdSe-sensitized photocathode coupling with Ni-substituted polyoxometalate catalyst for photoelectrochemical generation of hydrogen

In terms of photoelectrochemical(PEC)hydrogen evolution,substantial challenge still remains regarding the controllable fabrication of quantum dots(QDs)-sensitized photocathodes with enhanced visible-light absorption,efficient charge carrier separation,and directional migration at the electrode interface.In this work,the CdTe/CdSe QDs-sensitized photocathodes were delicately constructed on p-type NiO-coated indium tin oxide(ITO)electrodes by spin-coating approach.The resulting co-sensitized photocathode exhibits a favorable pseudo-Type Ⅱ energetic band alignment that combines the advantages of strong light absorption of constituent QDs as well as the effective and oriented charge separation and migration.Upon green LED light illumination,the photogenerated electrons could be effectively transferred to a tetra-nickel-substituted polyoxometalate catalyst for hydrogen production while photogenerated holes will be scavenged at the NiO/ITO electrode.Under minimally optimized conditions,the pseudo-Type Ⅱ CdTe/CdSe-sensrtized photocathode yields a photcx:urrent density of over 100 pA/cm^(2) and a Faradaic efficiency of〜100%,which is among one of the most efficient QDs-based photocathode systems coupling with Ni-substituted polyoxometalate catalyst for photoelectrochemical hydrogen generation.

光电化学分解水电池的电极性能提高方法及光阴极研究进展

光电化学水分解电池能够将太阳能直接转化为氢能,是一种理想的太阳能利用方式.p-n叠层电池具有理论转换效率高、成本低廉、材料选择灵活等优势,被认为是最具潜力的一类光电化学水分解电池.然而,目前这类叠层电池的太阳能转化效率还不高,主要原因是单个电极的效率太低.本文介绍了几种提高光电极分解水性能的方法—减小光生载流子的体相复合、表面复合以及抑制背反应等,同时综述了国内外关于几种p型半导体光阴极的研究进展,如Si、In P、Cu In1-xGaxS(Se)2、Cu2Zn Sn S4等.通过总结,作者提出一种p-Cu2Zn Sn S4(Cu In1-xGaxS(Se)2)/n-Ta3N5(Fe2O3)组装方式,有望获得高效低成本叠层光电化学水分解电池.

Conformal and continuous deposition of bifunctional cobalt phosphide layers on p-silicon nanowire arrays for improved solar hydrogen evolution

Vertically aligned p-silicon nanowire （SiNW） arrays have been extensively investigated in recent years as promising photocathodes for solar-driven hydrogen evolution. However, the fabrication of SiNW photocathodes with both high photoelectrocatalytic activity and long-term operational stability using a simple and affordable approach is a challenging task. Herein, we report conformal and continuous deposition of a di-cobalt phosphide （C02P） layer on lithography- patterned highly ordered SiNW arrays via a cost-effective drop-casting method followed by a low-temperature phosphorization treatment. The as-deposited C02P layer consists of crystalline nanoparticles and has an intimate contact with SiNWs, forming a well-defined SiNW@Co2P core/shell nanostructure. The conformal and continuous Co2P layer functions as a highly efficient catalyst capable of substantially improving the photoelectrocatalytic activity for the hydrogen evolution reaction （HER） and effectively passivates the SiNWs to protect them from photo-oxidation, thus prolonging the lifetime of the electrode. As a consequence, the SiNW@Co2P photocathode with an optimized C02P layer thickness exhibits a high photocurrent density of -21.9 mA·cm^-2 at 0 V versus reversible hydrogen electrode and excellent operational stability up to 20 h for solar-driven hydrogen evolution, outperforming many nanostructured silicon photocathodes reported in the literature. The combination of passivation and catalytic functions in a single continuous layer represents a promising strategy for designing high-performance semiconductor photoelectrodes for use in solar-driven water splitting, which may simplify fabrication procedures and potentially reduce production costs.

Manipulating metal-oxygen local atomic structures in singlejunctional p-Si/WO_(3) photocathodes for efficient solar hydrogen generation

Self-passivation in aqueous solution and sluggish surface reaction kinetics significantly limit the photoelectrochemical(PEC)performances of silicon-based photoelectrodes.Herein,a WO_(3) thin layer is deposited on the p-Si substrate by pulsed laser deposition(PLD),acting as a photocathode for PEC hydrogen generation.Compared to bare p-Si,the single-junctional p-Si/WO_(3) photoelectrodes exhibit excellent and stable PEC performances with significantly increased cathodic photocurrent density and exceptional anodic shift in onset potential for water reduction.It is revealed that the WO_(3) layer could reduce the charge transfer resistance across the electrode/electrolyte interface by eliminating the effect of Fermi level pinning on the surface of p-Si.More importantly,by varying the oxygen pressures during PLD,the collaborative modulation of W–O bond covalency and WO6 octahedral structure symmetry contributes to the promoted charge carrier transport and separation.Meanwhile,a large band bending at the p-Si/WO_(3) junction,induced by the optimized O vacancy contents in WO_(3),could provide a photovoltage as high as~500 mV to efficiently drive charge transfer to overcome the water reduction overpotential.Synergistically,by manipulating W–O local atomic structures in the deposited WO_(3) layer,a great improvement in PEC performance could be achieved over the singlejunctional p-Si/WO_(3) photocathodes for solar hydrogen generation.