Development of robust noble-metal free lanthanum, neodymium doped Li1.05Ni0.5Mn1.5O4 as a bifunctional electrocatalyst for electrochemical water splitting

Abstract

Catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are at the heart of water oxidation reactions. Despite continuous efforts, the development of OER/HER electrocatalysts with high activity at low cost remains a big challenge. Herein, we report a composite material consisting of Li_1.05Ni_0.5Mn_1.5O₄, Li_1.05Ni_0.5 La_0.10Mn_1.40O₄, and Li_1.05Ni_0.5 Nd_0.10Mn_1.40O₄ as a bifunctional electrocatalyst for OER and HER applications. Though the catalyst has a modest activity for HER, it exhibits high OER activity thereby making it a better nonprecious electrocatalyst for both OER and HER. The catalytic activity arises from the synergetic effects between LNM-La and LNM-Nd by a facile route that shows excellent and durable bifunctional catalytic activity for OER and HER in the alkaline medium developed. The LNM, LNM-La, and, LNM-Nd displayed current densities of 2.17 V, 1.68 V, and 1.93 V vs. RHE at 10 mA cm⁻² respectively. The Tafel slope values obtained for LNM, LNM-La, and LNM-Nd are about 419 mV dec⁻¹, 118 mV dec⁻¹, and 378 mV dec⁻¹ respectively. These results indicate the superior electrocatalytic activity of LNM-La with facile OER kinetics.