Nanoconfined Ni single-atom Ni–O–Ti atomic asymmetric sites for highly efficient and stable photocatalytic hydrogen evolution

Photocatalytic hydrogen production is a promising route toward sustainable energy conversion. However, the overall efficiency remains limited by severe charge recombination and low carrier utilization. Herein, asymmetric interfacial Ni–O–Ti sites were constructed via oxygen-defect-induced nanoconfinement, forming oxygen bridges between hollow TiO 2 nanospheres (HTNSs) and single–atom Ni species. The hollow TiO 2 nanosphere catalyst with oxygen defects and Ni single atoms (Ni/BHTNSs) exhibited a high hydrogen evolution activity of 816 μmol·h –1 , which is more than 80 times higher than that of pure TiO 2 . Experimental and theoretical analyses demonstrated that the oxygen defects and hollow structure accelerated the charge carrier separation and transfer, which significantly boosted the hydrogen generation. Compared with symmetric Ni–O–Ni coordination, the asymmetric Ni–O–Ti configuration shortens the Ni–O bond length, enabling more favorable linear H⁺ adsorption and electron accumulation while lowering the energy barrier for H 2 formation. These effects collectively accelerate hydrogen evolution kinetics. This work presents an atomic-level asymmetric site design coupled with nanoconfinement engineering, offering a robust strategy for efficient and stable photocatalytic water splitting.