Detailed surface vs. bulk composition studies of LaxCa1−xMnO3 oxides provide clear evidence that the ORR activity increases as the effective electron population at the Mn site increases.

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Abstract: The kinetics of the oxygen reduction reaction (ORR) at carbon supported transition metal oxides in alkaline solutions is systematically investigated as a function of the nature of the B-site. The study is focused on LaBO3 (B = Cr, Co, Fe, Mn and Ni) nanoparticles synthesized by an ionic liquid route, offering fine control over phase purity and composition. Activity towards the ORR was compared with commercial Pt/Etek catalyst. Detailed electrochemical analysis employing a rotating ring-disc electrode provides conclusive evidences that the carbon support plays an important contribution in the faradaic responses. Decoupling the contribution of the carbon support uncovers that the reactivity of LaMnO3 towards the 4e-ORR pathway is orders of magnitude higher than for the other lanthanides. We rationalise these observations in terms of changes in the redox state at the B-site close to the formal oxygen reduction potential.

A detrimental competition between the urea oxidation reaction (UOR) and oxygen evolution reaction is identified. Strategies are proposed to alleviate such competition and boost the performance of the UOR and other organic compound oxidation reactions.

Coating black silicon needles in a uniform layer of conducting boron-doped CVD diamond produces a high-surface-area electrode material that promising for electrochemical applications, as well as acting as a robust bactericidal surface.