Stepwise oxygen vacancy‑titanium ensemble engineering and phosphorus-doping strategy to boost rhodium...

The introduction of defects and heteroatoms into metal oxides represents an effective strategy for engineering the electronic environments and surface areas of active sites, thereby enhancing hydrogen production from ammonia borane hydrolysis (ABH). In this study, we fabricated oxygen vacancies (O_v), Ti³⁺ and phosphorus (P) heteroatom co-modified TiO₂ (P-TiO_2-X) as a robust platform to anchor ultrafine and electron-rich Rh nanoparticles (NPs). The modifications of O_v, Ti³⁺ and P motifs on TiO₂ co-constructed ultrafine and electron-rich Rh sites, facilitating the activation of H₂O molecules and the dissociation of OH bonds, which promoted hydrogen evolution from ABH. Consequently, the well-engineered Rh/P-TiO_2-X catalyst demonstrated a high turnover frequency of 1008 ± 18 min^-1 or 2313 ± 48 min^-1 based on Rh dispersion and a low activation energy of 28.5 ± 0.3 kJ·mol^-1. Despite undergoing six cycling tests, Rh/P-TiO_2-X maintained good stability. Additionally, demand-based hydrogen evolution could be achieved using Zn²⁺/EDTA-2Na as an "on-off" switch, allowing for flexible and efficient hydrogen utilization. This study presents a novel modification strategy involving O_v, Ti³⁺ and P motifs to co-create electron-rich Rh active sites, thereby facilitating high-efficiency and on-demand hydrogen production from ABH.