Tailoring the Nonmetal Elements in Carbon-Based Single-Atom Catalysts toward Hydrogen Energy Catalysis

Single-atom catalysts (SACs) have been intensively studied due to their merits including extremely high atom utilization, excellent catalytic activity, and unique selectivity. The catalytic activity of SACs is mainly regulated by factors including central metal atoms, the chelation atoms, and thereby the electronic structure of the SACs. Studies have shown that the alternation in heteroatom configuration can significantly tailor the catalytic performance, as the electronic structure of the center metal is highly sensitive to its chelating elements and coordination structure. In this review, we mainly focus on the influence of P and S doping on the catalytic activity of SACs from the perspectives of hydrogen energy conversion. The doping methods of S/P heteroatoms are first introduced in detail, with the active centers for multiheteroatom coordination identified using advanced characterization techniques. Then, through specific applications of SACs in oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), the superiority of multidoping over single doping is demonstrated, and the mechanism of S/P doping toward catalytic activity promotion is explained. Finally, future developments and challenges of multidoped atom coordination are discussed.