Co1Al2(OH)m Layered Double Hydroxide/Graphitic Carbon Nitride Composite Nanostructure: An Efficient Water Oxidation Reaction Electrocatalyst in an Alkaline Electrolyte

Abstract

Earth-abundant and noble-metal-free electrocatalysts are highly desirable for an efficient alkaline oxygen evolution reaction (OER). Herein, we report the cobalt aluminum hydroxide [Co1Al2(OH)m] supported on graphitic carbon nitride (g-CNx) composite materials for superior OER activity in alkaline conditions. One-pot microwave heating of aqueous solution of Co(NO3)2·6H2O and Al(NO3)3·9H2O in the presence of g-CNx successfully produced Co1Al2(OH)m nanosheets impregnated on g-CNx. The composite catalyst requires a low overpotential of 0.32 V to reach the current density of 10 mA cm–2 with a low value of the Tafel slope (36 mV/dec). The catalyst has very high mass activity and turnover frequency values of 1211 mA mg–1 and 0.62 s–1 at 0.35 V, which are ∼25 and 36 times higher compared to commercial IrO2, respectively. Most importantly, the electrocatalyst shows remarkably high stability compared to commercial IrO2 in alkaline medium. The two-dimensional sheet morphology, higher electrochemical surface area of the Co1Al2(OH)m layered double hydroxide (LDH)/g-CNx composite, and strong interaction between the support and Co1Al2(OH)m LDH nanosheets could be the reason for superior activity and durability of the composite material.