Abstract: Oxygen reduction reaction (ORR) is a key electrochemical process in energy storage and conversion devices such as fuel cells and metal-air batteries. ORR involves complex multi-electron and proton transfer processes, and its sluggish kinetics severely limits the energy conversion efficiency of these devices. Single-atom electrocatalysts (SACs) have emerged as a prominent focus in heterogeneous catalysis due to their high atomic utilization and unique electronic structures. Heteroatom doping serves as an effective strategy for modulating ORR performance. Among various heteroatoms, phosphorus (P) possesses lone pair electrons in its 3p orbitals, which can regulate the coordination microenvironment and charge distribution around the central metal atom, thereby tuning the adsorption/desorption strength of oxygen-containing intermediates and influencing ORR catalytic activity. This review systematically summarizes the regulatory mechanisms of P heteroatoms on the ORR performance of SACs, specifically in three aspects: (i) in the first coordination sphere, where P directly substitutes for N atoms coordinated to the central metal atom; (ii) in the second or third coordination sphere, or in more peripheral regions; and (iii) through regulation by phosphorus compounds. This review elucidates the mechanisms by which heteroatom P influences ORR performance and establishes guiding principles for the design and synthesis of high-activity and high-durability single-atom ORR electrocatalysts via heteroatom doping.

Key words: Phosphorus doping, Oxygen reduction reaction, Single-atom electrocatalyst