Co/CoP Heterojunction on Hierarchically Ordered Porous Carbon as a Highly Efficient Electrocatalyst for Hydrogen and Oxygen Evolution

• Published in: Advanced energy materials Vol. 11; no. 42
• Main Authors: Li, Wei, Liu, Jing, Guo, Peifang, Li, Haozhe, Fei, Ben, Guo, Yanhui, Pan, Hongge, Sun, Dalin, Fang, Fang, Wu, Renbing
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.11.2021
• Subjects: Carbon; Catalytic activity; Electrocatalysts; Electron transfer; Free energy; Heterojunctions; hydrogen evolution reaction; Hydrogen evolution reactions; Mass transfer; oxygen evolution reaction; Oxygen evolution reactions; Polystyrene resins; Pyrolysis; Water absorption; water splitting
• DOI: 10.1002/aenm.202102134
• ISSN: 1614-6832

Designing non‐precious electrocatalysts to synergistically achieve a facilitated mass/electron transfer and exposure of abundant active sites is highly desired but remains a significant challenge. Herein, a composite electrocatalyst consisting of highly dispersed Co/CoP heterojunction embedded within a hierarchically ordered macroporous‐mesoporous‐microporous carbon matrix (Co/CoP@HOMC) is rationally designed through the pyrolysis of polystyrene sphere‐templated zeolite imidazolate framework‐67 (ZIF‐67) assemblies. The combined experimental and theoretical calculations reveal that Co/CoP interfaces not only provide richly exposed active sites but also optimize hydrogen/water absorption free energy via electronic coupling, while the interconnected macroporous structure enables a superior mass transfer to all accessible active sites. As a result, the as‐developed Co/CoP@HOMC composites exhibit outstanding catalytic activity with overpotentials of only 120 and 260 mV at 10 mA cm−2 for the hydrogen evolution reaction and oxygen evolution reaction in 1.0 m KOH, respectively. Moreover, an alkaline electrolyzer constructed by Co/CoP@HOMC requires an ultralow cell voltage of 1.54 V to achieve 10 mA cm−2, outperforming that of the Pt@C||IrO2@C couple (1.64 V). Hierarchically ordered porous carbon‐supported heterostructured Co/CoP nanoparticles (Co/CoP@HOMC) are rationally designed. Owing to the synergistic coupling effect, highly exposed active sites, and enhanced mass transfer, the Co/CoP@HOMC exhibits an exceptional catalytic activity for both the hydrogen evolution reaction and the oxygen evolution reaction.