Abstract:
To determine the effect of Ba addition to LaCoO3 perovskite structures as efficient oxygen evolution reaction (OER) catalysts, we have synthesized different composite materials in the LaCoO3-BaCoO3 compositional series using a combinatorial sol-gel method. Rietveld refinement X-ray diffraction data reveals that no significant incorporation of Ba into the LaCoO3 structure, forming a solid solution, occurs with Ba addition. Rather, BaCoO3 and BaCO3 side phases are formed at higher amounts of Ba. As determined from X-ray photoelectron spectra, the surface oxygen contribution gets more pronounced at the expense of the lattice oxygen with increasing Ba content, pointing towards a higher number of oxygen species located near surface oxygen vacancies. In direct correlation, electrochemical activity measurements in the OER reaction reveal that the addition of Ba in the LaCoO3-BaCoO3 compositional series increases the beneficial influence of BaCoO3. The peak of maximum activity is observed for pure BaCoO3, with an at the same time low overpotential of 266 mV at 10 mA cm2 at excellent stability. Our results suggest a new generation of Ba-based perovskite materials with the potential to improve the electrochemical performance of current OER catalysts.
