Photosynthesis of H₂ and its storage on the Bandgap Engineered Mesoporous (Ni²⁺/Ni³⁺)O @ TiO₂ heterostructure

A noble-metal free and surface defect-induced mesoporous mixed valent NiO decorated TiO₂ heterostructure with tuned bandgap has been successfully prepared. Its outstanding visible-light driven hydrogen evolution and its excellent H₂ storage ability have been examined and confirmed. The formation of oxygen vacancies by surface defect creates the Ni³⁺ and Ti³⁺ on the interface of the heterostructure induce the efficient H₂ evolution, bench-marked by 1200% enhancement in catalytic performance. The underlying chemistries include the near-unity occupancy of e_g orbital (t_2g⁶ e_g¹) of Ni³⁺ which speeds up the electron transfer and significantly promote the excellent electron-hole separation efficiency, establishes the outstanding overall charge-transfer efficiency and long-term photocatalytic activity in the visible light spectrum. Multiple Ti³⁺ adsorption centers in the structure attract multiple intact H₂ molecules per each center via a sigma - pi bonding motif - namely the Kubas interaction - which leads to 480% higher H₂ adsorption capability against the performance of the pristine mesoporous TiO₂. Not only the significant results, the study also provide an air-stable synthetic method on the basis of low-cost and abundant materials, which are strongly favoured for scaling up production.