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Single atoms (SAs) have drawn significant attention, because of their enormous catalytic activity and high atom-utilization efficiency. Particularly, for H 2 evolution, SAs decorated on two-dimensional (2D) nanosheets have great potential, because of the distinctive advantages offered by 2D materials, such as abundant surfaceactive sites, high specific surface area, and better-photoexcited charge carrier separation. Despite the significant advantages of 2D materials as support, the deposition of SAs on 2D nanosheets is still a great challenge and rarely has been reported. This work reports the facile deposition of Pt-SAs and Pt-SAs/nanoclusters (NCs) on Ca 2 Nb 3 O 10 and Ndoped Ca 2 Nb 3 O 10−x N x nanosheets, respectively, via a modified photodeposition method. We observe that the presence of a suitable concentration of tetrabutylammonium (TBA + ) ions is essential for the successful deposition of Pt-SAs and Pt-SAs/NC via Pt−O bond formation on Ca 2 Nb 3 O 10 and Ca 2 Nb 3 O 10−x N x nanosheets, respectively. The findings of aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC HAADF-STEM) validated the successful deposition of Pt-SAs on Ca 2 Nb 3 O 10 and Pt-SAs/NC on N-doped Ca 2 Nb 3 O 10−x N x nanosheets, which are further validated via X-ray absorption fine structure (XAFS) spectroscopy. As a result, Ca 2 Nb 3 O 10 -Pt SA exhibited excellent H 2 production: 280.5 μmol h −1 , which is 2.7 and 6.1 times higher, compared to Ca 2 Nb 3 O 10 -Pt NP (105.08 μmol h −1 ) and bare Ca 2 Nb 3 O 10 (46.05 μmol h −1 ). Furthermore, N-doped Ca 2 Nb 3 O 10−x N x -Pt SA/NC demonstrated 2.0 and 3.6 times superior H 2 evolution, in contrast to Ca 2 Nb 3 O 10−x N x -Pt NP under full-spectrum and visible light irradiation (λ > 420 nm), respectively. Consequently, this work provides a new direction for SAs deposition on exfoliated perovskite nanosheets in the presence of TBA + ions used during exfoliation, offering a potential strategy that can be applied to a large library of nanosheets synthesized via softchemical exfoliation.

Efficient charge–carrier separation and their utilization are the key factors in overcoming sluggish four‐electron reaction kinetics involved in photocatalytic oxygen evolution. Here, a novel study demonstrates the significance of Na2S2O8 as a sacrificial agent in comparison to AgNO3. Resultantly, BiFeO3 (BFO) and titanium doped‐oxygen deficient BiFeO3 (Ti‐BFO‐R) nanostructures achieve ≈64 and 44.5 times higher O2 evolution in the presence of Na2S2O8 compared to AgNO3 as a sacrificial agent, respectively. Furthermore, the presence of Co single atoms (Co‐SAs) deposited via immersion method on BFO and Ti‐BFO‐R nanostructures led to achieving outstanding O2 evolution at a rate of 16.11 and 23.89 mmol g−1 h−1, respectively, which is 153 and 227.5 times higher compared to BFO (in the presence of AgNO3), the highest O2 evolution observed for BFO‐based materials to date. The successful deposition of Co‐SAs is confirmed by aberration‐corrected high‐angle annular dark‐field scanning transmission electron microscopy (AC HAADF‐STEM) and X‐ray absorption near‐edge structure (XANES). The charge transfer investigations confirm the significance of Co‐SAs on BFO‐based photocatalysts for improved charge–carrier separation, transport, and utilization. This novel study validates the excellent role of Na2S2O8 as a sacrificial agent and Co‐SAs as a cocatalyst for BFO‐based nanostructures for efficient O2 evolution.

Co 3 O 4 nanoparticles were synthesized by a green synthesis method using bread fungus and cobalt nitrate hexahydrate as the precursors. The effects of the calcination temperature on the structure and properties of nanoparticles, and the ambient temperature on the photocatalytic reaction are discussed. The cubic structure of Co 3 O 4 nanoparticles was obtained, and the grain size was between 14 and 19 nm at different calcination temperatures. Co 3 O 4 calcined at 500°C shows good photocatalytic performance. Without adding any sacrificial agent and cocatalyst, the amount of hydrogen and oxygen released in 5 h were 259.4 and 135.7 μmolg −1 , respectively. The results show that, with the increase of ambient temperature, the evolution rate of hydrogen and oxygen is accelerated, and the atomic ratio of hydrogen to oxygen is close to 2:1. In addition, the Co 3 O 4 photocatalyst has good stability. Our study provides an environmentally friendly, low-cost, and efficient method for the preparation of cobalt oxide photocatalysts with excellent performance.