Electrochemical Assessment of Refractory Metallic Catalysts for Application in Oxygen Evolution Reaction

The development of electrocatalysts for water splitting is a challenging issue for researchers in the field, because the oxygen evolution reaction (OER) occurs in multiple stages and with slow kinetics. In this study, Tungsten (W) and Molybdenum (Mo) (refractory metals) particles with a Body-Centered Cubic (BCC) structure were obtained through the high-energy milling of precursors Ammonium paratungstate (APT) and Ammonium heptamolybdate (AHM)) followed by reduction/decomposition in hydrogen (H2) atmosphere. It was found that particle size and oxygen vacancies strongly influence the catalytic activity of refractory metals. In fact, the W smaller particle/ crystallite size, confirmed by Scanning Electron Microscope (SEM) and X-ray diffraction (XRD) techniques, as well as the larger ratio O2/O1 = 0.81 determined by X-ray photoelectron spectroscopy (XPS), leads to a sharp increase in current density compared to Mo that have O2/O1 = 0.75. The W particles only require 322 mV vs. RHE to generate a current density of 10 mA cm-2, against 334 mV vs. RHE for Mo. The W showed superior electrocatalytic performance, with low overpotential, Tafel slope of 53 mV dec-1, CDL of 1.79 mF cm-2, ECSA of 44.75 cm2, the specific activity of 10.72 mA cm- 2, and mass activity of 2400 A g-1. Therefore, this two-step synthesis method is highly effective in producing catalysts with excellent electrochemical responses for energy applications.