Polyol Synthesis of Ni and Fe Co-Incorporated Tungsten Oxide for Highly Efficient and Durable Oxygen Evolution Reaction

The development of inexpensive transition metal-based catalysts for water splitting has attracted global attention, which should be accomplished in the simplest and most scalable way feasible. In this study, nickel and iron co-incorporated tungsten oxides (Ni x Fe 1-x WO 4 ) were synthesized using a simple polyol method, and the materials achieved a highly efficient and stable oxygen evolution reaction (OER) in an alkaline electrolyte. The product as-synthesized using the polyol method consisted of an undeveloped wolframite structure, which was converted to its complete crystal by heat treatment at 600 °C, with an increase in crystallite size. The OER properties of Ni x Fe 1-x WO 4 could be controlled by the ratio of Ni and Fe present and heat treatment temperature. A ternary tungsten oxide (Ni 0.5 Fe 0.5 WO 4 ) with a Ni:Fe:W molar ratio of 0.5:0.5:1 deposited on a glassy carbon electrode required 297 mV to reach a current density of 10 mA cm −2 in 1.0 M KOH solution. The 10 mA cm −2 electrolysis with the electrode was continued for at least 100 h. This was quite different from a similarly-synthesized NiFe oxide without W, which required an additional 47-mV overpotential to reach 10 mA cm −2 and had inferior durability.