Copper Selenides as High-Efficiency Electrocatalysts for Oxygen Evolution Reaction

Abstract

Designing high-efficiency water oxidation catalysts from earth-abundant resources has attracted significant attention in the last couple of years owing to the potential application of this technology in several energy conversion devices. Among the transition metals, copper is one of the cheapest earth-abundant nonprecious element which can enhance electrocatalytic activity due to heavily occupied d-orbitals. In this article we have shown electrocatalytic activity of copper selenide for the first time for water oxidation reaction. The copper selenide phases were synthesized by direct electrodeposition on electrodes, as well as by hydrothermal and chemical vapor deposition (CVD) techniques. Structure and morphology characterization through powder X-ray diffraction, Raman, X-photoelectron spectroscopy, and electron microscopy revealed that all the synthesized phases were pure crystalline copper selenide of composition Cu2Se and comprising nanostructured granular morphology. Electrocatalytic performance for water oxidation was investigated in alkaline solution (1 M KOH) and it was observed that Cu2Se showed a low overpotential of only 270 mV to achieve 10 mA cm–2. This catalyst also displayed a low Tafel slope of 48.1 mV dec–1. Interestingly Cu2Se showed comparable electrocatalytic activity irrespective of the method of synthesis indicating that it is indeed an intrinsic property of the material. Chronoamperometric studies revealed that the catalyst retained its activity for prolonged periods of continuous oxygen evolution exceeded 6 h, while postactivity characterization revealed that crystallinity and surface composition was preserved after catalytic activity. Because copper selenides can be found in nature as stable minerals, this article can initiate a new concept for efficient catalyst design.