Ternary Hierarchical Cu₇S₄/TiO₂/CoCr‐LDH Heterostructured Nanorod Arrays with Multiphase Reaction Interfaces for More Efficient Photoelectrochemical Water Splitting

Abstract

harvesting and converting solar energy into clean hydrogen and oxygen fuel is one of the most promising process to acquire inexhaustible clean energy and thus to fundamentally solve global energy crises. [2,3] As a critical component in the threeelectrode structured PEC cells, plenty of efforts have been made on the semiconductor photoelectrode. Since Fujishima and Honda succeeded in reporting the photoelectrolysis of water using a singlecrystal TiO 2 electrode in 1972 for the first time, [4] till now, multifarious nanostructured semiconductor materials, such as WO 3 , [5][6][7][8] Fe 2 O 3 , [9,10] ZnO, [11] TiO 2 , [12] and BiVO 4 , [13] have been extensively investigated and selected as candidates in PEC water splitting system due to their significant advantages including low cost, low-temperature solution fabrication technique, insensitivity of impurities, and high stability under working conditions. However, since the pristine metal oxides normally suffer from wide bandgap, high bulk recombination losses, poor holes transfer efficiency, and sluggish surface oxidation reaction, the exploitation of suitable electrode materials with high light-to-electricity conversion efficiency and excellent stability is highly imperative but still quite challenging. [14] As a typical wide bandgap semiconductor, TiO 2 is undoubtedly considered as an excellent photoanode candidate due to its favorable optical bandgap, sufficient positive valence band position for water oxidation, environmental compatibility, outstanding chemical stability, low toxicity, and earth abundance. [15] However, the PEC performance of TiO 2 -based photoanodes is severely hindered due to the slow surface water oxidation kinetics, which is originated from its wide bandgap, narrow optical-response range, and fast electronhole recombination. [16] Extensive efforts have been devoted to circumventing these drawbacks mentioned above and improving the performance, including sensitization with a narrow bandgap semiconductor, [14] elemental doping, [17] heterojunction construction, [18] hierarchical nanostructuring, [19] and surface modification, [20] which could not only increase the visible light absorption but also enhance the hole transfer efficiency. Among the various narrow bandgap semiconductors, metal Fabricating hierarchical and highly matched heterostructure with large surface areas and multiple interfaces is an effective approach to enhancing the photo electrochemical performance. Here, well-aligned hierarchical Cu 7 S 4 / TiO 2 /CoCr-layered double hydroxide (LDH) nanorod arrays are reported, aiming at accelerating charge separation and transfer kinetics. The modifications of Cu 7 S 4 and CoCr-LDH based on TiO 2 have endowed the photoanode a surprising enhancement in both ultraviolet light absorption and charge separation efficiency due to highly matched band alignment. The formation of heterojunction is an effective strategy to prevent photocorrosion of Cu 7 S 4 by attaching protective layers on Cu 7 S 4 . Moreover, other than the hierarchical morp...

Highly active deficient ternary sulfide photoanode for photoelectrochemical water splitting

“…Among others, metal sulfides have long been the topic of research, especially photocatalytic applications due to their suitable electronic bandgaps, exposed active sites, diverse and adjustable chemical structures 11 . However, apart from the factor of photochemical photocorrosion, which can be dramatically suppressed by the usage of sacrificial agents or surface decoration of passive layers [12][13][14] , the metal sulfides directly employed as photoanodes usually exhibit low photoinduced electron-hole separation efficiencies and sluggish surface water oxidation kinetics [15][16][17][18] , which limits the application of metal sulfides-based photoanodes. The defects in metal sulfide, especially for introducing sulfur vacancies, are evidenced as an effective strategy to enhance the photocatalytic and PEC properties [19][20][21][22] .…”

Engineering Layered Double Hydroxide–Based Photocatalysts Toward Artificial Photosynthesis: State‐of‐the‐Art Progress and Prospects

“…However, Cu 7 S 4 /TiO 2 has poor photostability, but with the addition of CoCr‐LDH, the photostability and the specific surface area of the nanohybrid remarkably improve for enhanced activity. [ 149 ] A similar phenomenon can be witnessed by TaON/Au/ZnCo‐LDH, which has a commendable synergic relationship, thus resulting in an astounding absorption range of 440–800 nm ( Figure a) with an optical bandgap of 2.13 eV to produce 0.206 min −1 of oxygen. This is plausible as both Au and ZnCo‐LDH act as light‐harvesting components to generate photoexcited electrons, which transfer to TaON.…”

Photoactive Tungsten-Oxide Nanomaterials for Water-Splitting

“…There are three different component systems with different morphology in which the hierarchy of the band structure observed for effective water-splitting. The main types of morphology include multi-heterojunction-based photocatalysts composed of WO 3 nanorods, Pt nanoparticles and TiO 2 nanoparticles [ 175 ], hierarchical heterostructures with core and double shells [ 176 ], rectangular AgIn(WO 4 ) 2 nanotubes which showed excellent photocatalytic properties for decomposing water to evolve H 2 [ 177 ] and linked porous structures such as WO 3 /porous–BiVO 4 /FeOOH [ 178 ]. Special attention should be paid to the three-component system made on spiral WO 3 nanostructures decorated with doped Mo and BiVO 4 nanoparticles [ 179 ].…”