Phosphorus-doped CoS2 nanoparticles with greatly enhanced electrocatalytic performance as Pt-free catalyst for hydrogen evolution reaction in acidic electrolyte

Abstract

In the present study, we have proposed the phosphorus (P)-doped CoS2 electrocatalyst through a simple hydrothermal route and utilized as an economical and earth-abundant electrocatalyst for hydrogen evolution reaction (HER). A sequence of P-doped CoS2 electrocatalysts were obatined by using different NaH2PO4 contents. The as-synthesized samples were characterized by XRD, SEM, HR-TEM, element mapping, and XPS analyses. It is found that these P-doped CoS2 materials composed of high purity nanoparticles and stacked in a block structure. The electrochemical performance has been investigated in 0.5-M H2SO4 electrolyte. The results indicate that the doping of phosphorus can significantly increase the electrocatalytic hydrogen evolution activity of CoS2. Among the different samples, the P-doped CoS2 attained with 5 mmol of NaH2PO4 contents offers the highest HER performance with a minimum overpotential of 109 mV at 10 mA cm-2, the smallest Tafel slope of 48 mV dec-1, and an excellent long-term durability over 1,000 cycles. The analysis results illustrate that the doped phosphorus may change the internal properties of CoS2, which promotes the ability of charge transfer and electrochemical active sites, resulting in the significantly increased HER activity compared with bare CoS2. Therefore, this work demonstrates that a proper doping of phosphorus is a suitable approach to improve the catalytic ability of metal sulfides for HER application.