Hydrothermal self-assembly of needle and sheet spherical array CuCo₂O₄ nanostructures on graphene aerogels for oxygen evolution reaction

Oxygen evolution reaction (OER) plays an important role in the field of renewable energy conversion. It is imminent to develop a highly active, inexpensive and easily available electrocatalyst. Here, we used hydrothermal method and calcination process to combine graphene aerogel with cobalt-copper-based oxide, and obtained two kinds of composite aerogel materials (CuCo₂O₄/GA) with different (needle spherical and sheet spherical) nanoarray morphology for catalyzing the oxygen evolution reaction. Compared with commercial catalyst Ir/C (338mV) and sheet spherical nanoarray CuCo₂O₄/GA (GCA-2) (292 mV), the needle spherical nanoarray CuCo₂O₄/GA (GCA-1) exhibits a lower overpotential (269 mV) to drive a current density of 10 mA/cm². At the same time, the Tafel slope of CGA-1 (87 mV dec⁻¹) is similar to Ir/C (88 mV dec⁻¹) and has the best kinetics of oxygen evolution reaction. Moreover, both the needle and sheet spherical nanoarray CuCo₂O₄/GA have excellent durability of 8 h. The optimized nanoarray CuCo₂O₄/GA has excellent electrocatalytic activity due to the successful combination of graphene aerogel substrate and cobalt-copper-based oxide, which together promotes the reversible reaction of the electrode-electrolyte interface during the oxygen evolution reaction. The electron conduction rate is increased, and the accessible reactive sites are increased. This article provides a simple and efficient morphological engineering strategy for designing and exploring electrocatalysts for oxygen evolution reactions.