Origin of the catalytic activity of phosphorus doped MoS₂ for oxygen reduction reaction (ORR) in alkaline solution: a...

Phosphorus doped MoS₂ nanosheets (P-doped MoS₂) 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 MoS₂ for ORR catalysis. The double P-doped MoS₂ (2P-MoS₂) is calculated to be more stable than the single P-doped MoS₂ (P-MoS₂), and the configuration with two P atoms in neighboring sites exhibits the highest stability. The surface of P-doped MoS₂ is found highly active for dissociation of O₂. Comparative calculations reveal that P-MoS₂ is unsuitable as ORR catalyst due to the high dissociation barrier of H₂O (1.19 and 2.06 eV for the first and second adsorbed H₂O), while the 2P-MoS₂ shows good ORR catalytic activity with much lower dissociation barrier of H₂O (0.62 eV). Furthermore, we elucidated that the ORR catalytic activity in 2P-MoS₂ originates from the activated S2 atom, which provides an extra adsorption site for the first H₂O and the following OH group benefited from the enhanced hydrogen bond interaction. Our results illustrate the mechanisms of doped MoS₂ based catalysts and provide rational way for designing ORR catalysts with high activity.