Designing thermodynamically stable noble metal single-atom photocatalysts for highly efficient non-oxidative conversion of ethanol into high-purity hydrogen and value-added acetaldehyde

The intrinsic surface atomic configuration of photocatalyst without unstable or difficult-to-generate atomic vacancies often limits the formation of effective interaction between metal single atom (MSA) cocatalyst and photocatalyst, thus inhibiting the stability and performance improvement of single-atom photocatalysts. In this study, we present a convenient and cost-effective photochemical oxygen reduction reaction (ORR) mechanism to prepare thermodynamically stable noble metal single-atom cocatalysts on TiO₂ photocatalyst under mild condition (only consuming water and oxygen at 101,325 ​Pa and 25 ​°C). The first-principles simulation firstly theoretically reveals that the intrinsic surface configuration of TiO₂ can only produce unstable Pt–O₂ structure. However, ORR occurring on TiO₂ can not only provide one foreign oxygen to coordinate with Pt single atom (PtSA), but also induce one surface lattice oxygen to move toward PtSA, promoting the formation of one thermodynamically stable Pt–O₄ species, demonstrated by the experimental synthesis of PtSA on TiO₂ in oxygen atmosphere instead of inert atmosphere. The obtained stable PtSA-TiO₂ photocatalysts exhibit a photocatalytic rate of 320.4 ​mmol·g⁻¹·h⁻¹ for the coproduction of high-purity hydrogen and value-added acetaldehyde with a selectivity of 99.65%, three-fold higher than the activity of Pt nanoparticles-loaded TiO₂. This strategy is further extended to other noble metals, such as Rh and Pd.