An interesting synergistic effect of heteronuclear dual-atom catalysts for hydrogen production: Offsetting or promoting

To elucidate the synergistic effect of dual-atom catalysts (DACs) at the microscopic level, we propose and construct a prototype heteronuclear system, CuNi/TiO₂, in which the two elements of a pair have significantly different d electron-donating abilities, as a piece in the puzzle. Using density functional theory calculations, we investigate charge-dependent configurations of Cu-Ni dimers anchored on TiO₂ by the mixing of individual constituent atoms. The d electron-donating ability determines deposition sequence and position of transition metal atoms on oxides, establishing dimer pattern and metal–support interactions. The interaction between Cu and Ni, beyond the coordination environment, predominately contributes to the synergistic effect. A complex adsorption–reduction behavior of H species on CuNi/TiO₂ is observed. The reaction mechanism and catalytic activity of CuNi/TiO₂ for hydrogen production are explored. At room temperature and high H coverages, CuNi/TiO₂ shows better performance and efficiency than Ni₁/TiO₂. Our findings provide a new understanding of the synergistic effect on structure–activity relationships of supported dimers, which would be beneficial in the future design of various DACs or even atomically dispersed metal catalysts.