Origin of the catalytic activity of phosphorus doped MoS(2) for oxygen reduction reaction (ORR) in alkaline solution: a theoretical study

Phosphorus doped MoS(2) nanosheets (P-doped MoS(2)) have been reported as excellent oxygen reduction reaction (ORR) catalysts with four-electron selectivity in alkaline solution. By performing density functional theory (DFT) calculations, we revealed the detailed reaction mechanism and the key reaction sites on surface of P-doped MoS(2) for ORR catalysis. The double P-doped MoS(2) (2P-MoS(2)) is calculated to be more stable than the single P-doped MoS(2) (P-MoS(2)), and the configuration with two P atoms in neighboring sites exhibits the highest stability. The surface of P-doped MoS(2) is found highly active for dissociation of O(2). Comparative calculations reveal that P-MoS(2) is unsuitable as ORR catalyst due to the high dissociation barrier of H(2)O (1.19 and 2.06 eV for the first and second adsorbed H(2)O), while the 2P-MoS(2) shows good ORR catalytic activity with much lower dissociation barrier of H(2)O (0.62 eV). Furthermore, we elucidated that the ORR catalytic activity in 2P-MoS(2) originates from the activated S2 atom, which provides an extra adsorption site for the first H(2)O and the following OH group benefited from the enhanced hydrogen bond interaction. Our results illustrate the mechanisms of doped MoS(2) based catalysts and provide rational way for designing ORR catalysts with high activity.