Interface engineering of ultrathin nickel metallene on titanium dioxide nanosheets for efficient photocatalytic...

Interfacial charge transfer plays a decisive role in determining photocatalytic hydrogen evolution efficiency, yet its potential remains underexplored in photocatalyst structural design. Here, an ultrathin two-dimensional (2D) Ni metallene is synthesized and employed as a cocatalyst with titanium dioxide(TiO₂) nanosheets for the first time, constructing an efficient 2D/2D photocatalytic architecture. Distinct from conventional approaches that rely on noble-metal loading or multimetallic synergy, this system achieves a pronounced activity enhancement through the structural engineering of earth-abundant Ni. The resulting Ni metallene/titanium dioxide(Ni-ene/TiO₂) composite delivers a hydrogen evolution rate of 8277 µmol h^-1 g^-1 under simulated solar irradiation, representing a 24-fold improvement over pristine TiO₂. The superior activity is mainly ascribed to the 2D metallic Ni metallene, which establishes a large-area interfacial contact with TiO₂, in contrast to conventional Ni nanoparticles with limited interfacial coupling, a conclusion further supported by density functional theory calculations. Notably, Ni metallene also exhibits effective cocatalytic activity when loaded onto 2D graphitic carbon nitride (g-C₃N₄) nanosheets, indicating that its interfacial advantages are transferable beyond TiO₂-based systems. Overall, this work establishes interfacial structural engineering of earth-abundant nickel as a powerful strategy for boosting photocatalytic hydrogen evolution, offering a new paradigm for designing high-performance noble-metal-free cocatalysts through interface-driven optimization.