Highly Efficient, Remarkable Oxygen Reduction Reaction (Orr) Activity of Vanadium Doped Mayenite Electride Nanocomposite

Abstract

Low-carbon emission is very critical for high energy production, which us to explore high performance electrocatalyst for fuel cells. Therefore for high performance electrocatalyst, we study to synthesize vanadium doped mayenite electride, C12A7-xVx:e- (where, C = CaO, A = Al2O3, and doping level, x = 0-1) (thereafter, simply expressed as V-C12A7:e-) nanocomposite with reduced graphene oxide (rGO), by employing a facile synthesis protocol based on modified sol-gel method. Herein, the highest obtained conductivity of synthesized composite was 440 S·cm-1 and the electron concentration measured by iodometry was ~2.5×1021 cm-3 at 300 K with “V” doping level x = 1. The significantly manifested more positive onset potential, and limited current density of 1.35 V, and 5.9 mA∙cm-2, was obtained, respectively, which were higher than the benchmark Pt/C (20%) requirement (0.98 V, 5.2 mA∙cm-2) in alkaline/acidic medium. Also, this synthesized composite shows superior selectivity to the desired four-electron pathway. In acidic medium, again heat treated V-C12A7:e- nanocomposite shows compatible performance to benchmark Pt/C (20%) in terms of ORR activity, current density, stability, and methanol tolerance. In real systems, the maximum power density reached to 240, 285 and 330 mW/cm2 for the benchmark Pt/C, the as-synthesized V-C12A7:e- nanocomposite, and again-heat-treated V-C12A7:e- nanocomposite, respectively. The high ORR activity is ascribed to the co-existence of extrinsic doped element, rGO and sufficient metallic V-C12A7:e-, causing a faster electron movement as well as better adsorption of oxygen molecules and keep their long time electrical stability. With the high ORR activity, the V-C12A7:e- nanocomposite can be used as an efficient, novel, lowest cost, potential non-Pt electrocatalyst in future fuel-cell industry.

Keywords: Vanadium doped C12A7:e-, conductivity enhancement, rGO coating, ORR, fuel cells