An Operando Investigation of (Ni-Fe-Co-Ce)O_x System as Highly Efficient Electrocatalyst for Oxygen Evolution Reaction

Abstract

The oxygen evolution reaction (OER) is a critical component of industrial processes such as electrowinning of metals and the chlor-alkali process. It also plays a central role in the developing renewable energy field of solar-fuels generation by providing both the protons and electrons needed to generate fuels such as H_2 or reduced hydrocarbons from CO_2. To improve these processes, it is necessary to expand the fundamental understanding of catalytically active species at low overpotential, which will further the development of novel electrocatalysts with high activity and durability. In this context, performing experimental investigations of the electrocatalysts under realistic working regimes, i.e. under operando conditions, is of crucial importance. Here, we study a highly active quinary transition metal oxide-based OER electrocatalyst by means of operando ambient pressure X-ray photoelectron spectroscopy and X-ray absorption spectroscopy performed at the solid/liquid interface. We observe that the catalyst undergoes a clear chemical-structural evolution as a function of the applied potential with Ni, Fe and Co oxy-hydroxides comprising the active catalytic species. While CeO_2 is redox inactive under catalytic conditions, its influence on the redox processes of the transition metals boosts the catalytic activity at low overpotentials, introducing an important design principle for the optimization of electrocatalysts and tailoring of novel materials.