Abstract:

Transition-metal based hybrids with excellent stability and activity are favorable candidates for hydrogen evolution reaction (HER). The development of typical Co₃S₄ has recently received considerable attention due to the multiple valences of the spinel-structured compound. However, the in-depth effect of the dopants on the HER performance of Co₃S₄ has not been systematically clarified. Here, we report a sequential synthesis of a spinel-structured cobalt phosphosulfate nanoneedle arrays grown on carbon cloth (namely, P-Co₃S₄/CC). Results indicate that P-Co₃S₄/CC exhibits high electrocatalytic performance for HER with a low overpotential of 65 mV to drive10 mA cm^-2, a small Tafel slope of 76.6 mV per decade, and great long-term stability for 25 h at various current densities in alkaline electrolyte. The first-principle calculation result reveals that the phosphorous doping work at Co₃S₄ enhances the HER performance significantly because the tetrahedral Co²⁺ active sites nearest the P atoms more easily weaken the H-O bond to form intermediates. The experiment result characterization and theoretical calculations further show that the introduction of P atom not only offers more active sites but also improves the electrical conductivity in an alkaline electrolyte solution. Consequently, the identification of active species provides feasible guidance for the further design of high-performance spinel-structured catalysts.

Key words: P-Co₃S₄/CC, P substitution, Electronic conductivity, HER