Electrosynthesis of CuO Nanocrystal Array as a Highly Efficient and Stable Electrocatalyst for Oxygen Evolution Reaction

Electrodeposition of active catalysts on electrodes appears as a convenient approach to prepare non-noble-metal based electrocatalysts with defined micro- and nano-structures. Herein we report a new strategy of fabricating a 3-D hierarchical CuO nanocrystal array (CuO NCA) on Cu foam through a two-step sacrifice-template method. This CuO NCA possesses high conductivity, great stability, and impressive catalytic activity for oxygen evolution reaction (OER) in alkaline electrolytes. The CuO NCA can achieve a high current density of 100 mA/cm^2 at a relatively low overpotential of 400 mV for OER, which shows a better performance than other Cu-based OER catalysts and IrO_2. The high activity of CuO NCA is well retained during a 10-h OER test at a high current density around 270 mA/cm^2, which is about 10 times higher than the current density achieved by IrO_2 (around 25 mA/cm^2) with the same applied overpotential. According to our best knowledge, CuO NCA is currently the most efficient and stable Cu-based electrocatalyst for water oxidation in alkaline electrolytes.