Cobalt-substituted iron-based wolframite synthesized via polyol route for efficient oxygen evolution reaction

Abstract

Binary tungsten oxides with a wolframite crystal structure, such as FeWO4 and CoWO4, have poor electrocatalytic activity for the oxygen evolution reaction (OER). However, the incorporation of a third element into the crystalline framework increased the OER activity in an alkaline medium. Specifically, Co0.5Fe0.5WO4 prepared through a polyol route generated a current density of 10 mA cm−2 at a considerably small overpotential (η) and Tafel slope (331 mV and 36.8 mV dec−1, respectively). This overpotential value was superior to those of Co0.5Fe0.5WO4 fabricated through a conventional hydrothermal route (η at 10 mA cm−2 = 360 mV) and commercial RuO2 (365 mV), a benchmark catalyst for the OER. The turnover frequency (TOF) of the polyol-synthesized Co0.5Fe0.5WO4 was estimated to be 0.235 s−1 at an overpotential of 400 mV, while stable operation at 10 mA cm−2 was maintained for at least 24 h.

Keywords

• Wolframite
• Polyol method
• Oxygen evolution reaction
• Ternary tungstates