Two‐Dimentional Nanostructured Metal Oxide/Sulfide–Based Photoanode for Photoelectrochemical Water Splitting

Abstract

The utilization of solar energy plays a vital role in relieving energy crisis and associated environmental problems. Photoelectrochemical (PEC) water splitting, which can directly transform solar energy into clean hydrogen energy, is one of the most promising strategies to utilize solar energy. 2D nanostructured metal oxides/sulfides have been widely applied as photoanodes in PEC cells due to their unique configuration and features, which can efficiently improve light absorption, enlarge electrode/electrolyte contacting interfaces, and promote carrier transfer and injection. This article begins with the introduction of performance parameters, carrier dynamics measurement, and mechanism exploration techniques for photoanodes, which is followed by an overview of research progress in using 2D nanostructure metal oxides/sulfides to fabricate efficient photoanodes for PEC water splitting. Subsequently, the recent representative strategies to optimize the PEC performance of 2D metal oxides/sulfides photoanodes, including structure engineering, defect engineering, element doping, heterojunction construction, and surface modification, are summarized. Finally, the exciting advances and future research directions for designing highly efficient 2D photoanodes are provided.

Few-Layer ZnIn2S4/Laponite Heterostructures: Role of Mg2+ Leaching in Zn Defect Formation

“…Photocatalysis is an effective means of utilization of solar energy for chemical transformation and environmental remediation. − However, due to the narrow spectral range of sunlight, improving photocatalytic efficiency for practical applications remains a major challenge. , To address these shortcomings, photocatalysts with a suitable band gap, efficient charge transfer capability, and low cost are sought for solar energy conversion. Two-dimensional (2D) semiconductors with tunable band gaps and unique photophysical properties have shown much promise for photocatalysis in recent years. − Among various layered semiconductor materials, the ternary metal sulfide ZnIn 2 S 4 (ZIS) represents an interesting material for photocatalysis due to its narrow band gap, photostability, and high visible light absorption range. − To date, numerous approaches to enhance its photocatalytic performance have been carried out, including shape, crystal facet, defect, and interface engineering. − Among these, constructing ultrathin nanostructures of ZnIn 2 S 4 can tune its photophysical properties to facilitate improved photocatalysis.…”

Enhanced Light Trapping and Charge Separation via Pyramidal Cu2O/NiCo-LDH Photocathode for Efficient Water Splitting

“…The sustainable energy economy urgently needs cheap and efficient solar chemical storage methods. The direct solar energy conversion to chemical fuels is listed among those most hopeful solutions to address the problem. , Water splitting based on photoelectrochemistry (PEC) arouses great concern as a straightforward and effective route for achieving solar energy conversion into chemical energy, for instance, renewable H 2 production from PEC water splitting. − Mickle metal oxide semiconductor materials such as Cu 2 O (2.0 eV), CaFe 2 O 4 (1.9 eV), CuFeO 2 (1.5 eV), and CuNb 3 O 8 (1.5 eV) show p-type conductivity due to mental vacancies defects, thus can be employed as photocathodes. − Among them, Cu 2 O has emerged as one of the candidate materials with nontoxicity, simple production, and low cost, as well as prominent photovoltage and photocurrent properties. At the 2.0 eV band gap, theoretically, Cu 2 O allows the efficiency in water splitting solar energy conversion to hydrogen up to 18%. − …”

Interfacial Bi–S bonds modulate band alignment for efficient solar water oxidation

“…Under the influence of an internal electric field, the photo-generated electrons on the conduction band of semiconductors with a relatively lower Fermi level ( E F ) can transfer to the valence band of semiconductors with higher E F values, thus modulating the band bending and realizing the Z-scheme charge transfer. 23 Furthermore, the existence of interfacial chemical bonds may change the work function of materials forming heterojunctions, which in turn affects the E F and internal electric field of heterojunctions. 24 Therefore, an efficient Z-scheme heterojunction can be obtained by reasonably modulating the interfacial chemical bond within the heterojunction.…”