Composition-controlled ultrathin holey TiO1_ xNx nanosheets as powerful hybridization matrices for highly mass-efficient electrocatalysts

Highly porous holey inorganic nanosheets have received growing attention as emerging 2D nanostructures because of their excellent functionalities as active materials and hybridization matrices. Here we report the composition-controlled synthesis of ultrathin holey metal oxynitride nanosheets with subnanometer-level thickness of ~0.8 nm and tunable defect/surface structures. The application of the obtained holey TiO1_xNx nanosheets as immobilization substrates allowed to maximize mass electrocatalytic activity of hybridized Pt nanoclusters via enhanced interfacial interaction at defective sites. The strong electronic coupling between positively-charged Pt nanoclusters and holey TiO1_xNx nanosheets with interfacial oxygen linkers enabled to achieve a superior electrocatalytic performance for hydrogen evolution reaction with an unusually high gravimetric efficiency (20.8 AmgPt_ 1), i.e., one of the most efficient values for Pt nanostructures. Density functional theory calculations and in-situ Raman analysis emphasize the significant contributions of interfacial oxygen linker in holey TiO1_xNx substrates and positive charge of Pt nanocluster to optimizing the electrocatalytic activity. The present study underscores that employing composition-controlled holey TiO1_xNx nanosheets as immobilization substrates provides a novel efficient methodology to explore high-performance electrocatalysts via the improvement of charge/mass transport and electrocatalytic kinetics, and the optimization of d-band center upon hybridization.