Efficient ORR catalysts for zinc-air battery: Biomass-derived ultra-stable Co nanoparticles wrapped with graphitic layers via optimizing electron transfer

Abstract

The poor stability of non-noble metal catalysts in oxygen reduction reaction (ORR) is a main bottleneck that limits their big-scale application in metal-air batteries. Herein, we construct a chainmail catalyst (Co-NC-AD) with outstanding stability, via the competitive complexation and post absorption strategy, consisting of highly graphitic layers wrapped uniform-size Co nanoparticles (Co-NPs). Experiments combined with density functional theory (DFT) calculations jointly confirmed that the electron transfer occurred from the inner Co-NPs to the external graphitic layers. It facilitated the adsorption process of oxygen molecules and the hybridization of the O-2p and C-1p orbitals, which accelerated the ORR reaction kinetics. Consequently, our prepared Co-NC-AD shows excellent ORR activity, offered with a more positive initial potential (Eonset = 0.95 V) and half-wave potential (E1/2 = 0.86 V). The remarkable stability and resistance of methanol poisoning are merited from the protection effect of stable graphitic layers. In addition, the high electrochemical performance of Co-NC-AD-based zinc-air battery demonstrates their potential for practical applications. Therefore, our work provides new ideas for the design of nano-confined catalysts with high stability and activity.