A Facile Approach for Pt Single Atoms Deposition on Two-Dimensional Calcium Niobate Nanosheets for Photocatalytic Hydrogen Evolution

Single atoms (SAs) have drawn significant attention, because of their enormous catalytic activity and high atom-utilization efficiency. Particularly, for H2 evolution, SAs decorated on two-dimensional (2D) nanosheets have great potential, because of the distinctive advantages offered by 2D materials, such as abundant surface-active 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 Ca2Nb3O10 and N-doped Ca2Nb3O10–xNx 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 Ca2Nb3O10 and Ca2Nb3O10–xNx 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 Ca2Nb3O10 and Pt-SAs/NC on N-doped Ca2Nb3O10–xNx nanosheets, which are further validated via X-ray absorption fine structure (XAFS) spectroscopy. As a result, Ca2Nb3O10-PtSA exhibited excellent H2 production: 280.5 μmol h–1, which is 2.7 and 6.1 times higher, compared to Ca2Nb3O10-PtNP (105.08 μmol h–1) and bare Ca2Nb3O10 (46.05 μmol h–1). Furthermore, N-doped Ca2Nb3O10–xNx-PtSA/NC demonstrated 2.0 and 3.6 times superior H2 evolution, in contrast to Ca2Nb3O10–xNx-PtNP 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 soft-chemical exfoliation.