Copper\nSelenides as High-Efficiency Electrocatalysts\nfor Oxygen Evolution Reaction

Abstract

Designing high-efficiency\nwater oxidation catalysts from earth-abundant\nresources has attracted significant attention in the last couple of\nyears owing to the potential application of this technology in several\nenergy conversion devices. Among the transition metals, copper is\none of the cheapest earth-abundant nonprecious element which can enhance\nelectrocatalytic activity due to heavily occupied <i>d</i>-orbitals. In this article we have shown electrocatalytic activity\nof copper selenide for the first time for water oxidation reaction.\nThe copper selenide phases were synthesized by direct electrodeposition\non electrodes, as well as by hydrothermal and chemical vapor deposition\n(CVD) techniques. Structure and morphology characterization through\npowder X-ray diffraction, Raman, X-photoelectron spectroscopy, and\nelectron microscopy revealed that all the synthesized phases were\npure crystalline copper selenide of composition Cu₂Se and\ncomprising nanostructured granular morphology. Electrocatalytic performance\nfor water oxidation was investigated in alkaline solution (1 M KOH)\nand it was observed that Cu₂Se showed a low overpotential\nof only 270 mV to achieve 10 mA cm^–2. This catalyst\nalso displayed a low Tafel slope of 48.1 mV dec^–1. Interestingly Cu₂Se showed comparable electrocatalytic\nactivity irrespective of the method of synthesis indicating that it\nis indeed an intrinsic property of the material. Chronoamperometric\nstudies revealed that the catalyst retained its activity for prolonged\nperiods of continuous oxygen evolution exceeded 6 h, while postactivity\ncharacterization revealed that crystallinity and surface composition\nwas preserved after catalytic activity. Because copper selenides can\nbe found in nature as stable minerals, this article can initiate a\nnew concept for efficient catalyst design.