Boosting oxygen reduction via MnP nanoparticles encapsulated by N, P-doped carbon to Mn single atoms sites for Zn-air batteries

Abstract

An electrocatalyst of single-atomic Mn sites with MnP nanoparticles (NPs) on N, P co-doped carbon substrate was constructed to enhance the catalytic activity of oxygen reduction reaction (ORR) through one-pot in situ doping-phosphatization strategy. The optimized MnSA-MnP-980℃ catalyst exhibits an excellent ORR activity in KOH electrolyte with a half-wave potential (E1/2) of 0.88 V (vs. RHE), and the ORR current density of MnSA-MnP-980℃ maintained 97.9 % for over 25000 s chronoamperometric i-t measurement. When using as the cathode, the MnSA-MnP-980℃ displays a peak power density of 51 mW cm−2 in Zinc-Air batteries, which observably outperformed commercial Pt/C (20 wt%). The X-ray photoelectron spectroscopy reveal that the doped P atoms with a strong electron-donating effectively enhances electron cloud density of Mn SAs sites, facilitating the adsorption of O2 molecules. Meanwhile, the introduction of MnP NPs can regulate the electronic structure of Mn SAs sites, making Mn SAs active sites exist in a low oxidation state and are less positively charged, which can supply electrons for ORR process to narrow the adsorption energy barrier of ORR intermediates. This work constructs novel active sites with excellent ORR properties and provides valuable reference for the development of practical application.