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

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, L 1 ) and 2-methylimidazole (MeMI, L 2 ) as ligands with the ratio of 2:5, Co 2+ and Zn 2+ as metal centers. Based on the concept of acid-base neutralization reaction, the proton-transfer induced “deprotonation and protonation” for L 1 and L 2 , respectively. Thus, the coordination was dominated by the deprotonated L 1 . Owing to also partial of protonated L 2 adsorbed as “counter ions”, carbonization of the obtained precursor at 800 °C under N 2 atmosphere endows the pyrolysis product with nitrogen-doped carbon supported metal pyrophosphate (M 2 P 2 O 7 @NC). Thus, the resulting M 2 P 2 O 7 @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 H 2 SO 4 , it only needs an over potential of 180 mV to realize a current density of 10 mA cm −2 .