Oxygen evolution catalysis in alkaline conditions over hard templated nickel-cobalt based spinel oxides

In this work, two series of cobalt-based spinel catalysts, Co3O4 and NiCo2O4, were synthesised by a hard template method with SBA-15 and were investigated as non-noble catalysts for the oxygen evolution reaction (OER) under basic conditions. The effect of synthesis conditions, i.e., heating rate and calcination temperature, and the addition of minor amounts of iron were evaluated with respect to the OER activity. Moreover, the influence of the alkali cation type in the electrolyte (Li, Na, K) was also evaluated. The highest activity was found for the NiCo2O4 obtained with the lowest heating rate. The increase in the heating rate and calcination temperature results in the decrease of the available surface area for the reaction, leading to the deterioration of the activity. The incorporation of 3 wt.% of iron in the lattice of NiCo2O4 and Co3O4 resulted in a decrease of the OER activity, however, the deactivation was much less severe in the case of NiCo2O4 than for Co3O4. Among the alkaline electrolytes used, KOH resulted in the highest catalytic activity both for NiCo2O4 and Co3O4.