Insights into the Mo-Doping Effect on the Electrocatalytic Performance of Hierarchical CoxMoyS Nanosheet Arrays for Hydrogen Generation and Urea Oxidation

Energy-efficient, low-cost, and highly durable catalysts for the electrochemical hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) are extremely important for related sustainable energy systems. In the present work, hierarchical coassembled cobalt molybdenum sulfide nanosheets deposited on carbon cloth (CC) were synthesized as catalysts for hydrogen evolution and urea oxidation. By adjusting the doping amount of Mo, 2D nanosheets with different morphologies and compositions (CoxMoyS-CC) can be obtained. The as-prepared nanosheet materials with abundant active sites exhibit superior properties on the electrochemical HER and UOR in alkaline medium. Significantly, the Mo-doping concentration and composition of the formed nanosheets have large effects on the electrocatalytic activity. The fabricated nanosheets with optimal Mo doping (Co3Mo1S-CC) illustrate the best catalytic properties for the HER in N2-saturated 1.0 M KOH. A small overpotential (85 mV) is needed to meet the current density of 10 mA/cm2. This study indicates that the doping of an appropriate amount of molybdenum into CoS2 nanosheets can efficiently improve the catalytic performance. Also, the nanosheet catalyst exhibits an extremely high electrocatalytic activity for the UOR, and the electrochemical results indicate that a relatively low cell voltage of 1.50 V is needed to obtain the current density of 10 mA/cm2. The present work demonstrates the potential application of CoMoS nanosheets in the energy electrocatalysis area and the insights into performance-boosting through heteroatom doping and optimization of the composition and structure.