Cation modulation in dual-phase nickel sulfide nanospheres by pulsed laser irradiation for overall water splitting and methanol oxidation reaction

Abstract

The development of a non-precious and highly active multifunctional electrocatalyst is essential for obtaining efficient electrochemical energy storage and conversion devices. Nickel derivate occupies the most important place when it comes to the transition metal-based electrocatalyst. In this study, we used a simple and extremely effective controllable pulsed laser irradiation (PLI) technique to fabricate dual-phase nickel sulfide, and we studied cation modulation using Co and Cu atoms. The multifunctional activity was witnessed by the performances of oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and methanol oxidation reaction (MOR) measured in an alkaline medium. The cation adjustment resulted in the improvement of the catalytic performance of HER and OER during Cu and Co substitution, respectively. For the Co-Ni-S sample in OER, we achieved an overpotential of 368 mV at 10 mA/cm2 in OER. The higher ECSA Cu-Ni-S sample improved HER activity at a lower overpotential of 271 mV at 10 mA/cm2 and a lower Tafel slope of 98 mV/dec. The excellent bifunctional activity enhanced overall water splitting with a lower voltage of 1.88 V to achieve a geometrical current density of 10 mA/cm2, with high durability. Meanwhile, the high selectivity of Cu resulted in a very high methanol electrooxidation activity with a current density as high as 55.4 mA/cm2. The detailed electrochemical studies were presented with their supporting physiochemical analysis. This report shows the efficiency and simplicity of fabricating transition metal derivatives and cation modulation using superficial laser methods.