Catalysis of the oxygen evolution reaction in strongly acidic electrolytes with earth-abundant crystalline nickel-manganese antimonate

Abstract

Many technologies that store renewable energy in chem. bonds rely on the oxygen evolution reaction (OER) to produce a renewable oxidant. In systems with an alk. electrolyte the OER is catalyzed by earth-abundant oxyhydroxides of the first-row transition metals, whereas systems with acidic electrolytes rely on noble metal oxides such as RuO_2 or IrO_2. The discrepancy in earth-abundance of OER catalysts in alk. and acidic electrolytes corresponds to the thermodn. instability of many first-row transition metal binary oxides in acidic conditions. Understanding how to stabilize first-row transition metals in acidic electrolytes while retaining catalytic activity towards the OER is a key milestone towards the development of scalable renewable energy technologies. We report herein a nickel-manganese antimonate OER electrocatalysts with a rutile-type crystal structure. The crystallinity of the nickel-manganese antimonate catalyst prevents dissoln. of Ni and Mn under operating conditions and at open circuit. The nickel-manganese antimonate catalyst operates at an initial overpotential of 672 ± 9 mV at 10 mA cm^(-2) of geometric c.d., and operates at an overpotential below 745 mV for 168 of continuous operation at 10 mA cm^(-2). The electrode surface, electrode bulk, and electrolyte were characterized with XPS, TEM, SEM, and ICP-MS. Surface and electrolyte measurements indicate initial preferential leaching of Mn from the electrocatalyst, followed by a leach rate of zero for Ni, Mn, and Sb after 120 h of continuous operation. The observations suggest an approach towards the development of earth-abundant, highly-activate electrocatalysts for the oxygen evolution reaction in strongly acidic conditions.