Particle size-controlled synthesis of high-performance MnCo-based materials for alkaline OER at fluctuating potentials

Abstract

For the large-scale generation of hydrogenviawater electrolysis the design of long term stable and active catalysts for the oxygen evolution reaction (OER) remains a key challenge. Most catalysts suffer from severe structural corrosion that becomes even more pronounced at fluctuating potentials. Herein, MnCo based cubic particles were preparedviaa hydrothermal approach, in which the edge length of the micron-sized particles can be controlled by changing the pH value of the precursor solution. The cubes are composed of varying amounts of MnCo2O4, CoCO3and a mixed (Mn/Co)CO3phase. Structure-activity relationships were deduced revealing a volcano-type behavior for the intrinsic OER activity and fraction of spinel oxide phase. A low overpotential of 0.37 V at 10 mA cm−2and a stability of more than 25 h was achieved in 1.0 M KOH using a rotating disc electrode (RDE) setup. The best performing catalyst material was successfully tested under dynamic process conditions for 9.5 h and shows a superior catalytic activity as anode for the overall water splitting in an electrolyser setup in 1.0 M KOH at 333 K compared to a reference NiCo-spinel catalyst.