N-Doped amorphous MoS_x for the hydrogen evolution reaction

Herein, the functions of a N dopant in crystalline MoS₂ catalysts during the electrochemical hydrogen evolution reaction (HER) were reported via a combined experimental and first-principles approach. However, studies on the N doping of amorphous MoS_x, which is a more active catalyst, have not been reported to date. In this study, via a simple method, we fabricated N-doped amorphous MoS_x for the first time and studied the correlations between the N dopant and the HER performance. Via X-ray photoelectron spectroscopy and theoretical formation energy calculations, we have found that a N dopant in basal plane S^2- plays a very important role in the improvement of the HER performance and remains stable during this dynamic transformation process. A N dopant in basal plane S^2- can increase the number of active sites toward the HER and enhance the conductivity of the catalysts as well as a N dopant in c-MoS₂. In addition to this, the first-principles calculations further suggested that a N dopant in basal plane S^2- could improve the activity of unsaturated Mo^V active sites by bringing its hydrogen adsorption free energy closer to zero. As a result, N-doped amorphous MoS_x possesses an overpotential of 143 mV at 10 mA cm^-2 and a Tafel slope of 57 mV dec^-1, much better than those of a-MoS_x. These results provide useful insights for the future development of nonmetal-doped MoS_x catalysts in the HER.