Insights into catalytic roles of noble-metal-free catalysts CoxSy for reduction of 4-nitrophenol

Abstract

To develop noble-metal-free catalysts, three Co_xS_y samples, i.e. Co₉S₈, CoS and CoS₂, have been prepared and investigated for the reduction of 4-nitrophenol. Co₉S₈ has the best surface electron immigration efficiency and the highest H₂-adsorption capability, which make it the most promising catalyst. On the other hand, CoS has higher electron transfer efficiency than CoS₂, leading to stronger H absorption capability. As a result, the catalytic activity of the three catalysts shows the following trend: Co₉S₈ > CoS > CoS₂ under the same reaction conditions. Finally, a plausible catalytic mechanism has also been proposed, which is helpful in acquiring an in-depth insight into the catalytic role of Co_xS_y.