Water Splitting Using a Photocatalyst with Single-Atom Reaction Sites

Abstract

Nanosheets doped with isolated single-atom reaction sites for hydrogen evolution are a potential means of suppressing recombination during photocatalytic water splitting. Oxide nanosheets show higher activity during photocatalytic hydrogen evolution from CH 3 OH/water after doping with singleatom reaction sites in the lattice. However, water splitting into H 2 and O 2 from pure water has not yet been achieved on such materials because backward reactions, such as oxygen reduction, are also accelerated at these same reaction sites. In the present study, calcium niobate nanosheets incorporating Rh single-atom reaction sites covered with ultrathin NiO x atomic layers are fabricated. The nanosheets having a Ni/Rh atomic ratio of 7/1 are found to promote evolution of H 2 and O 2 from water. In this system, the ultrathin NiO x atomic layers prevent oxygen penetration but allow H + to access the Rh reaction sites, thus promoting photocatalytic water splitting for H 2 and O 2 production. This is the first demonstration of perfect water splitting using a nanosheet photocatalyst with single-atom reaction sites.

Single-atom catalysts for high-efficiency photocatalytic and photoelectrochemical water splitting: distinctive roles, unique fabrication methods and specific design strategies

“…80,81 Reducing the particle size of cocatalysts to NPs, NCs and SAs, improving the active site dispersion, increasing the specific surface area, and tailoring the electronic structure and morphology of the substrate are reported to be effective in increasing the number of active sites for surface redox reactions in photocatalytic water splitting. 82–85 Among them, tuning the electronic structure of the substrate and reducing the particle size of cocatalysts are particularly effective in boosting the photocatalytic activity due to some additional benefits brought about by these two strategies including simultaneously enhanced light-harvesting and charge transfer capability. 57,86,87…”

“…80,81 Reducing the particle size of cocatalysts to NPs, NCs and SAs, improving the active site dispersion, increasing the specic surface area, and tailoring the electronic structure and morphology of the substrate are reported to be effective in increasing the number of active sites for surface redox reactions in photocatalytic water splitting. [82][83][84][85] Among them, tuning the electronic structure of the substrate and reducing the particle size of cocatalysts are particularly effective in boosting the photocatalytic activity due to some additional benets brought about by these two strategies including simultaneously enhanced light-harvesting and charge transfer capability. 57,86,87 Although most of the photocatalysts with excellent activity for photocatalytic water splitting cannot be directly applied to photoelectrochemical water splitting because of their poor electrochemical activity, the basic principles of photoelectrochemical water splitting are similar to those of photocatalytic water splitting, also involving three steps, lightharvesting, charge carrier separation/transfer and surface redox reactions.…”

Photocatalytic overall water splitting by graphitic carbon nitride

“…Catalyst size control is now an energetic research frontier for the whole catalysis field since within some ranges the smaller particle size with more active sites can lead to the better catalytic activity in principle. Single atom cocatalyst development is now attracting the increasing attention with the potential to achieve the breakthrough of photocatalytic water splitting 39–41 . Its high activity and selectivity can significantly decrease the usage of catalyst loading, which is viewed as a crucial step to achieve the low‐cost photocatalysis since most of the high performance cocatalysts are now still noble‐metal based.…”

Recent Progress in the Synthesis and Applications of Composite Photocatalysts: A Critical Review

“…As a result, the photoactivity of the catalyst for selective CO 2 conversion was remarkably improved. According to the recent report by Hsu et al [406] the nanosheets of calcium niobate incorporated single atom Rh reactive sites shielded by ultrathin atomic layered NiOx catalyst exhibited enhanced photocatalytic performance for water splitting to generate H 2 and O 2 . In this complex system, the ultrathin atomic layered NiOx prevented the oxygen penetration but allowed H + to access the reactive sites of Rh, thereby promoted the generation of H 2 and O 2 through H 2 O splitting.…”