NNaTaO₃@Ta₃N₅ Core‐Shell Heterojunction with Controlled Interface Boosts Photocatalytic Overall Water Splitting

Abstract

Ta3N5 is a promising material for photocatalytic hydrogen production from water because of its suitable band structure for both solar energy collection and overall water splitting, while its application is restricted by severe charge recombination as well as non‐equilibrium redox capabilities. Herein, atomic‐scale N‐doped NaTaO3@Ta3N5 (NNaTaO3@Ta3N5) core‐shell cubes prepared by nitridation of cubic NaTaO3 are reported. The core‐shell heterojunction cubes present efficient and stoichiometric evolution of H2 and O2 from photocatalytic overall water splitting, with a quantum efficiency of 2.18% at 550 nm without any cocatalyst. The success relies on the Ta3N5 shell having a thickness of only ≈5 nm which enables increased lifetimes of the photogenerated charges. Moreover, the core‐shell heterojunction shows a type‐I band alignment that can steer smooth charge flow from NNaTaO3 to Ta3N5, particularly with the assistance of the shared communal Ta atoms at the interface. This efficiency can be further improved to 6.28% by in situ deposition of a Rh@Cr2O3 core‐shell cocatalyst, which is among the highest reported values over Ta3N5‐based photocatalyst. This study offers a promising pathway for the construction of well‐defined heterojunctions with manipulated charge transfer behavior for photocatalytic overall water splitting.

Enhancing the Photocatalytic Activity of CaTaO2N for Overall Water Splitting through Surface Nitride Ion Enrichment

“…In the case of the Ca 2p spectra in Figure d, the Ca 2p 3/2 and Ca 2p 1/2 doublet peaks appear at 345.5 and 349.3 eV, respectively, and the areas of these peaks are almost unchanged following the renitriding process. Figure c displays Ta 4f high-resolution XPS data, which contain two groups of doublet peaks at 26.7/24.8 and 25.7/23.8 eV, corresponding to Ta–N and Ta–O bonds, respectively . It should be noted that the intensity of the Ta–N peaks increases with increasing heating time during the renitridation, indicating a greater degree of nitridation of the NCTON, in accordance with the N 1s XPS and XRD results.…”

“…In other work, Lu et al. reported that modification to increase the nitrogen content is a promising means of tuning charge transfer characteristics to enhance photocatalytic overall water splitting …”

Emerging transition metal nitrides in solar energy conversion: design strategies and future perspectives for efficient photocatalysis

“…46,51 With the assistance of Rh@CrO x core–shell cocatalyst, the solar-to-hydrogen efficiency for overall water splitting of the reported Ta 3 N 5 -based semiconductor photocatalyst has achieved 0.09%. 52 In addition to the orthorhombic Ta 3 N 5 , the hexagonal TaN has also shown potential applications in various photocatalytic reactions. 53…”

“…52,78 For instance, it has been reported that this N-doped NaTaO 3 /Ta 3 N 5 core–shell heterojunction facilitates the smooth and rapid migration of photogenerated charge carriers to the surface active sites. 52 Additionally, the combination of different materials in the heterojunctions can leverage the advantages of each component, thereby achieving enhanced photocatalytic performance. Depending on the specific photocatalytic reaction, the surface of TMN photocatalysts can be loaded with reducing co-catalysts or oxidizing co-catalysts.…”

“…79,80 For high-efficiency TMN-based photocatalysts, it is often preferred to simultaneously construct heterojunctions and load co-catalysts to achieve spatial separation of charge carriers and enable photocatalytic oxidation and reduction reactions to occur at different reaction active sites. 46,52 In fact, the construction of composite materials has become a necessary approach to achieve industrial-level efficiency for TMN-based photocatalysts.…”