Application of changing the valence state of metals through the reaction time for efficient oxygen evolution reaction

Abstract

Although many types of efficient non-precious metal catalysts have been developed as efficient catalysts for oxygen evolution reaction (OER), their application potential remains limited due to their complex synthesis processes. To overcome this shortcoming, novel FeNi sulfide catalysts loaded on carbon nanotubes (CNTs) (FeNiS/CNTs) were synthesized via a one-step process at room temperature and pressure for OER. The valence states of the metal in the catalysts could be regulated by changing the reaction time. The catalytic activity for the OER could be enhanced by adjusting the metal valence states in the obtained catalyst. Furthermore, altering the metal ratio allowed for further optimization of the catalyst. As a result, the obtained catalyst FeNiS/CNTs demonstrated excellent OER activity. Electrochemical tests indicated that FeNiS/CNTs has a lower overpotential and smaller Tafel slope, and needs a mere 230 mV overpotential to obtain a current density of 10 mA cm⁻², and its Tafel slope was only 45 mV dec⁻¹. Also, it demonstrated a high turnover frequency (TOF) of greater than or equal to 1.97 s⁻¹ when the overpotential was 300 mV. This synthesis strategy also offers new insights for other OER catalysts.