Effect of Surface Charge Distribution of Phosphorus-Doped MoS<sub>2</sub> on Hydrogen Evolution Reaction
Chunlian Peng, Lili Song, Lian Wang, Fan Yang, Jianjun Ding, Fangzhi Huang, Yuqiao Wang
Abstract
MoS2 used for effective hydrogen evolution mainly depends on the activity of Mo–S edge sites. The exposure of abundant active edge sites has become an important way to broadly enhance the MoS2 catalytic activity. However, it is difficult to establish a visual evaluation method to determine the intrinsic catalysis of MoS2. Herein, the effect of surface charge distribution of phosphorus-doped MoS2 on hydrogen evolution can be visually described by mapping the differential charge density. The design and analysis are based on density functional theory calculations with the comparison of the electronic structure before and after nonmetal atom doping. Furthermore, the atom interaction before and after doping can be extracted by the projected crystal orbital Hamiltonian population (pCOHP). The bond strength between sulfur and hydrogen atoms is measured with the integrated COHP (ICOHP). Due to electronegativity difference, phosphorus doping causes the electron rearrangement around Mo and S atoms. The doped phosphorus acts as a bridge to more uniformly improve the charge gradient distribution between Mo and S atoms. Meanwhile, phosphorus doping reduces the hydrogen adsorption energy on the S atom surface, ensuring that the free energy of hydrogen evolution is effectively reduced by moderate doping. The hydrogen evolution reaction can achieve a low overpotential of 152 mV at 1 mA cm–2, a Tafel slope of 86 mV dec–1, and a continuous 30 h operation. We have explored an effective method for designing efficient catalysts by combining theory with experiment.