Site-coverage dependent single-atom-layer catalysts toward hydrogen production

Engineering the site density of single-atom catalysts (SACs) on a confined catalyst surface has great potential to improve catalytic performances. Especially, the dispersed status of single metal atoms and optimal site distributions are crucial during the catalytic process. Here, using integrated theoretical and experimental approaches, we demonstrate an optimal single Pt site coverage (about 0.34 Pt/nm2) over a CdS-confined Pt single-atom-layer surface for high-effective hydrogen evolution. A volcanic-type relation between hydrogen products and Pt site densities is found when progressively increasing Pt concentrations. Further theory calculations show the individual Pt monomer within the CdS matrix could trigger an effect radius (about 8.6 Å) to weaken the hydrogen adsorption of neighbor S atoms and enhance hydrogen products. This radial range will lead into an optimal density distribution of 0.33 Pt/nm2 to maximally activate the whole surface. Furthermore, the interactions between overly dense Pt monomers will deteriorate the adsorption and desorption behaviors of hydrogen.