Rationally designed/constructed MnOx/WO3 anode for photoelectrochemical water oxidation

The activity of WO₃ photoanode could be improved efficiently after loading MnO_x by photodeposition. The maximum photocurrent density of composite photoanode is achieved with a deposition time of 3 min, which is higher than that of pristine WO₃ photoanode around 40%.     

Nanostructure-based WO3 photoanodes for photoelectrochemical water splitting

Nanostructured WO(3) has been developed as a promising water-splitting material due to its ability of capturing parts of the visible light and high stability in aqueous solutions under acidic conditions. In this review, the fabrication, photocatalytic performance and operating principles of photoelectrochemical cells (PECs) for water splitting based on WO(3) photoanodes, with an emphasis on the last decade, are discussed. The morphology, dimension, crystallinity, grain boundaries, defect and separation, transport of photogenerated charges will also be mentioned as the impact factors on photocatalytic performance.     

Efficient photoelectrochemical water splitting by anodically grown WO3 electrodes

The potentiostatic anodization of metallic tungsten has been investigated in different solvent/electrolyte compositions with the aim of improving the water oxidation ability of the tungsten oxide layer. In the NMF/H(2)O/NH(4)F solvent mixture, the anodization leads to highly efficient WO(3) photoanodes, which, combining spectral sensitivity, an electrochemically active surface, and improved charge-transfer kinetics, outperform, under simulated solar illumination, most of the reported nanocrystalline substrates produced by anodization in aqueous electrolytes and by sol-gel methods. The use of such electrodes results in high water electrolysis yields of between 70 and 90% in 1 M H(2)SO(4) under a potential bias of 1 V versus SCE and close to 100% in the presence of methanol.     

Facile synthesis of Ni-doped WO3 nanoplate arrays for effective photoelectrochemical water splitting

Journal of Solid State Electrochemistry - A two-step hydrothermal process for preparing Ni-doped WO3 nanoplate arrays (NPAs) is developed, and the obtained samples were used as a photoanode to...     

WO3 homojunction photoanode: Integrating the advantages of WO3 different facets for efficient water oxidation

The manipulation of the surface property of WO₃ photoanode is the main breakthrough direction to improve its solar water oxidation performance both in thermodynamics and kinetics.Here,we report a WO₃(002)/m-WO₃ homojunction film that is composed of an upper WO₃ layer with predominant(002)facet(WO₃(002))and a lower WO₃ layer with multi-crystal facets(m-WO₃)as a photoanode for solar water oxidation.Due to the synergistic effect of WO₃(002)layer and m-WO₃ layer,better water oxidation activity and stability are achieved on the WO₃(002)/m-WO₃ homojunction film relative to the m-WO₃ and WO₃(002)film.Specifically,the improved water oxidation performance on the WO₃(002)/m-WO₃ homojunction film is attributed to the followings.In thermodynamics,the band position differences between WO₃(002)layer and m-WO₃ layer lead to the formation of WO₃(002)/m-WO₃ homojunction,which has positive function of improving their charge separation and transfer.In kinetics,the upper WO₃(002)layer of the WO₃(002)/m-WO₃ film has superior activity in the adsorption and activation of water molecules,water oxidation on this homojunction film photoanode is inclined to follow the four-holes pathway,and the corrosion of photoanode from the H₂O₂ intermediate is restrained.The present work provides a new strategy to modify the WO₃ photoanodes for thermodynamically and kinetically efficient water oxidation.     

Unravelling the essential difference between TiOx and AlOx interface layers on Ta3N5 photoanode for photoelectrochemical water oxidation

Tantalum nitride(Ta₃N₅) is a very promising photoanode material due to its narrow band gap(2.1 eV)and suitable band alignment for solar water splitting.However,it suffers from severe photocorrosion during water oxidation.In this work,it was found that surface passivation by AlO_x and TiO_x layers results in dramatically different PEC performance of Ta₃N₅ photoanode for water oxidation.The mechanism study indicates that the negative ...     

g-C_3N_4基多功能层光阳极在光电化学水分解中的应用（英文）

光电化学分解水制氢可以一并解决环境问题和能源危机,因而成为研究热点.由于TiO_2 禁带宽度较大,不能有效吸收太阳光中的可见光,使光电化学分解水制氢的应用受限.g-C_3N_4的禁带宽度约为2.7 e V,能有效吸收可见光,但g-C_3N_4薄膜制备研究较少.我们通过热聚缩合法直接在FTO导电玻璃上制备出g-C_3N_4薄膜,发现其光电化学分解水制氢稳定性不高,选择易制备的TiO_2 作为保护层可以提高g-C_3N_4的耐用性.此外,为提高g-C_3N_4光生电子空穴对的分离能力,依靠Co-Pi对光生空穴的捕获作用而将其覆盖在最外层.因此本文首次制备一种新型的g-C_3N_4/TiO_2 /Co-Pi光阳极用于光电化学分解水制氢,其中g-C_3N_4用作光吸收层,TiO_2 用作保护层,Co-Pi用作空穴捕获层.并在此基础上,通过扫描电子显微镜(SEM),X射线衍射(XRD),紫外可见光谱(UV-Vis)等手段研究了g-C_3N_4/TiO_2 /Co-Pi光阳极的形貌特征和光电化学性能.SEM、EDS和XRD结果表明,g-C_3N_4/TiO_2 /Co-Pi光阳极被成功制备在了FTO导电玻璃上,厚度约为3μm.UV-Vis测试表明,g-C_3N_4的光吸收边约为470 nm,可以有效地吸收可见光,并且g-C_3N_4的框架结构使光多次反射折射增加了光的捕获能力,由此可见,g-C_3N_4能够发挥很好的光吸收层作用.通过对g-C_3N_4光阳极,g-C_3N_4/TiO_2 光阳极和g-C_3N_4/TiO_2 /Co-Pi光阳极的电流电压测试发现,g-C_3N_4/TiO_2 光阳极的光电流密度小于g-C_3N_4光阳极,而g-C_3N_4/TiO_2 /Co-Pi光阳极的光电流密在可逆氢电极1.1 V下达到了0.346 mA?cm–2,约为单独g-C_3N_4光阳极的3.6倍.这说明Co-Pi是提升g-C_3N_4光电化学性能的主要因素.电化学阻抗测试结果发现,g-C_3N_4/TiO_2 /Co-Pi光阳极的界面电荷转移电阻小于g-C_3N_4光阳极的,这表明g-C_3N_4/TiO_2 /Co-Pi光阳极界面处载流子转移较快,同时也能促进内部光生电子空穴对的分离,整体性能的提高应该主要归因于Co-Pi对光生空穴的捕获作用.恒电压时间测试展示出g-C_3N_4/TiO_2 /Co-Pi光阳极的光电流密度在2 h测试过程中没有明显下降,表明g-C_3N_4/TiO_2 /Co-Pi光阳极是相当稳定的,具有良好的耐用性,归因于TiO_2 和Co-Pi的共同保护作用,主要归因于TiO_2 层对FTO导电玻璃上的g-C_3N_4薄膜保护,从电化学沉积Co-Pi到所有测试结束.总体而言,g-C_3N_4/TiO_2 /Co-Pi光阳极加强的光电化学性能归因于以下几个因素:(1)g-C_3N_4优异的光吸收能力;(2)TiO_2 稳定的保护提升了g-C_3N_4薄膜的耐用性;(3)Co–Pi对光生空穴的捕获有效促进了光生电子空穴对的分离.     

Improvement of the photoelectrochemical performance of vertically aligned WO3 nanosheet array film with a disordered surface layer by electroreduction

Journal of Solid State Electrochemistry - The search for efficient and powerful photoanode materials remains one of the toughest challenges in photoelectrochemical (PEC) water splitting because the...     

Si-doped Fe2O3 nanotubular/nanoporous layers for enhanced photoelectrochemical water splitting

The present work reports the enhancement of the photoelectrochemical water splitting performance of in-situ silicon (Si)-doped nanotubular/nanoporous (NT/NP) layers. These layers were grown by self-organizing anodization on Fe-Si alloys of various Si content. The incorporation of Si is found to retard the layer growth rates, leads to a more pronounced nanotubular morphology, and most importantly, an improved photoelectrochemical behavior. By increasing Si content from 1, 2 to 5 at.% in the iron oxide NT/NP photoanodes, the photocurrent onset potential shifts favorably to lower values. At 1.3 V vs. RHE, hematite layer with 5 at.% Si shows a 5-fold increase of the photocurrent, i.e. 0.5 mA cm^− 2 in comparison to 0.1 mA cm^− 2 for the undoped samples. The study also reveals that a suitable layer thickness is essential to achieve a beneficial effect of the Si doping.     

Direct Z-scheme WO3-x nanowire-bridged TiO2 nanorod arrays for highly efficient photoelectrochemical overall water splitting

All-solid-state Z-scheme photocatalysts for overall water splitting to evolve H2 is a promising strategy for efficient conversion of solar energy.However,most o...     

镍修饰WO3膜光电化学氧化水的研究

在强碱性溶液中低电压低电流条件下在W基底上经阳极氧化得到致密WO3层,而后在酸性条件下在WO3表面经光辅助电化学还原沉积镍,所获得的复合电极具有优异的光电化学氧化水的活性和稳定性.SEM,EDX,XPS和TEM等表征表明复合电极中具有体心立方结构的W基底经阳极氧化形成了具有单斜结构的WO3层,表面修饰的镍物种以Ni(OH)2形式存在.光电化学实验表明WO3层对可见光具有良好的光响应,表面修饰镍后,光电氧化水的起始电位显著降低,电极的稳定性也得以提高.     

电沉积WO_3薄膜及其光电性能的表征

本文采用电化学法制备了均匀、附着力强的WO3薄膜,研究了不同沉积电位和不同的沉积时间对薄膜的光电性能影响,并使用了XRD,UV-vis,M-S,光电流光谱(IPCE)等分析表征手段对薄膜进行了表征。实验结果表明,所制得的WO3薄膜为单斜晶系,退火后沿(200)晶面择优生长;对比所有沉积电位,-0.45 V沉积电位(vs.SCE)所获得的WO3薄膜均匀致密,薄膜的带边在460 nm(≈2.7 eV),其光电转换性能最好;在实验范围内薄膜越厚,其光电转换性能越好。     

Interfacial design of new generation of dye-sensitized photoelectrochemical cells for water oxidation

正Artificial photosynthesis involves the conversion of solar energy, water, and CO2into chemical fuels and oxygen. One of the most challenging steps is the production of oxygen from water oxidation, as it involves multi-electron and proton transfer processes. Recently, dye-sensitized photoelectrochemical cells (DSPECs) have been widely investigated as the devices to attain the goal of water oxidation. Generally, these devices are comprised of a wide band gap semiconductor, typically TiO2or SnO2, a molecular chromophore as a sensitizer, and a water oxidation catalyst     

Determining the role of oxygen vacancies in the photoelectrocatalytic performance of WO3 for water oxidation

Oxygen vacancies are common to most metal oxides, whether intentionally incorporated or otherwise, and the study of these defects is of increasing interest for solar water splitting. In this work, we examine nanostructured WO₃ photoanodes of varying oxygen content to determine how the concentration of bulk oxygen-vacancy states affects the photocatalytic performance for water oxidation. Using transient optical spectroscopy, we follow the charge carrier recombination kinetics in these samples, from picoseconds to seconds, and examine how differing oxygen vacancy concentrations impact upon these kinetics. We find that samples with an intermediate concentration of vacancies (∼2% of oxygen atoms) afford the greatest photoinduced charge carrier densities, and the slowest recombination kinetics across all timescales studied. This increased yield of photogenerated charges correlates with improved photocurrent densities under simulated sunlight, with both greater and lesser oxygen vacancy concentrations resulting in enhanced recombination losses and poorer J–V performances. Our conclusion, that an optimal – neither too high nor too low – concentration of oxygen vacancies is required for optimum photoelectrochemical performance, is discussed in terms of the competing beneficial and detrimental impact these defects have on charge separation and transport, as well as the implications held for other highly doped materials for photoelectrochemical water oxidation.

A medium concentration of oxygen vacancies (V_O ≈ 2%) is critical to the performance of WO₃ photoanodes for solar water oxidation, enhancing charge separation and reducing recombination across all timescales examined.     

WO3 coatings for photoelectrochemical synthesis of persulfate: efficiency,stability and applicability

Journal of Solid State Electrochemistry - Light-assisted electrochemical processes have the potential to replace energy-intensive electrosynthesis technologies, especially in the area of strong...     

A co-activation strategy for enhancing the performance of hematite in photoelectrochemical water oxidation

Hematite(α-Fe_2O_3) is a promising photoanode for photoelectrochemical(PEC) water splitting.However,the severe charge recombination and sluggish water oxidation kinetics extremely limit its use in photohydrogen conversion.Herein,a co-activation strategy is proposed,namely through phosphorus(P)doping and the loading of CoAl-layered double hydroxides(CoAl-LDHs) cocatalysts.Unexpectedly,the integrated system,CoAl-LDHs/P-Fe_2O_3 photoanode,exhibits an outstanding photocurrent density of 1.56 mA/cm~2 at 1.23 V(vs.reversible hydrogen electrode,RHE),under AM 1.5 G,which is 2.6 times of pureα-Fe_2O_3.Systematic studies reveal that the remarkable PEC performance is attributed to accelerated surface OER kinetics and enhanced carrier separation efficiency.This work provides a feasible strategy to enhance the PEC performance of hematite photoanodes.     

The effects of adjusting pulse anodization parameters on the surface morphology and properties of a WO3 photoanode for photoelectrochemical water splitting

Journal of Solid State Electrochemistry - An ordered porous nanostructure provides a large reaction interface with an unusually high number of active sites, meaning that such a nanostructure is...     

Unraveling the role of Ti_3C_2 MXene underlayer for enhanced photoelectrochemical water oxidation of hematite photoanodes

Hematite is regarded as a promising photoanode for photoelectrochemical(PEC) water splitting.However,the charge recombination occurred at the interface of FTO/hematite strictly limits the PEC performance of hematite.Herein,we reported a Ti3C2 MXene underlayer modified hematite(Ti-Fe2O3) photoanode via a simple drop-casting followed by hydrothermal and annealing processes.Owing to the bifunctional role of Ti3C2 MXene underlayer in improving the interfacial properties of FTO/hematite and providing Ti source for the construction of Fe2 TiO5/Fe2O3 heterostructure in hematite nanostructure,the bulk and interfacial charge transfer dynamics of hematite are significantly enhanced,and consequently enhancing the PEC performance.Compared with the pristine hematite,the as-prepared Ti-Fe2O3 photoanode shows an increased photocurrent density from 0.80 mA/cm² to 1.30 mA/cm² at 1.23 V vs.RHE.Moreover,a further promoted PEC performance including a dramatically increased photocurrent density of 2.49 mA/cm² at1.23 V vs.RHE and an obviously lowered onset potential is achieved for the Ti-Fe2O3 sample after the subsequent surface F-treatment and the loading of FeNiOOH cocatalyst.Such results suggest that the introduction of Ti3C2 MXene underlayer is a facile but effective approach to improve the PEC water splitting activity of hematite.     

Electrodeposited Cu thin layers as low cost and effective underlayers for Cu2O photocathodes in photoelectrochemical water electrolysis

Journal of Solid State Electrochemistry - Cu2O is one of the most studied semiconductors for photocathodes in photoelectrochemical water splitting (PEC-WS). Its low stability is counterbalanced by...