Highly active M2P2O7@NC (M = Co and Zn) for bifunctional electrocatalysts for ORR and HER

Abstract

Tuning the coordination environment between metal centers and organic ligands is a promising way to design of the precursors of electrocatalysts for water splitting or other renewable energy options. In this work, a novel coordinated polymer was prepared feasibly in polyvinyl pyrrolidone (PVP) aqueous solution using aminotrimethylene phosphonic acid (ATMP, L1) and 2-methylimidazole (MeMI, L2) as ligands with the ratio of 2:5, Co2+ and Zn2+ as metal centers. Based on the concept of acid-base neutralization reaction, the proton-transfer induced “deprotonation and protonation” for L1 and L2, respectively. Thus, the coordination was dominated by the deprotonated L1. Owing to also partial of protonated L2 adsorbed as “counter ions”, carbonization of the obtained precursor at 800 °C under N2 atmosphere endows the pyrolysis product with nitrogen-doped carbon supported metal pyrophosphate (M2P2O7@NC). Thus, the resulting M2P2O7@NC exhibits the enhanced and durable ORR and HER performance. For ORR in 0.1 M KOH, an enhanced onset potential (0.925 V vs. RHE), half wave potential (0.793 V vs. RHE) and diffusion limiting current (6.132 mA cm−2) can be obtained comparable to those of Pt/C. For HER in 0.5 M H2SO4, it only needs an over potential of 180 mV to realize a current density of 10 mA cm−2.