Optimization of Hydrogen Evolution Performance in ZnIn₂S₄ Photocatalysts via Ho-Doped Induced Tensile Strain

The photocatalytic hydrogen evolution (PHE) is a crucial technique for converting solar energy into green hydrogen. However, the PHE efficiency remains limited by metal-acid site spacing. In this study, we present a lattice-strain strategy to precisely control the distance between the metal and acid site by doping rare-earth Ho atoms onto a ZnIn₂S₄ nanosheet. Ho-doped ZnIn₂S₄ exhibits a hydrogen evolution rate of 1865.49 µmol g^-1 h^-1 under visible light, approximately 2.4 times that of the pure sample, with an apparent quantum efficiency of 14.7% at 420 nm. This performance is attributed to precise control of the distance between metal and acid sites via tensile strain induced by Ho, resulting in greatly improved charge-transfer capability and reduced energy barrier of the reaction. This work provides new insights into the design of highly efficient photocatalysts via strain engineering, revealing the role of the metal-acid site distance as a crucial structural parameter in the synergistic regulation of charge dynamics and the thermodynamics of hydrogen evolution.