Polymer-Mediated Self-Assembly of Amorphous Metal-Organic Complexes toward Fabrication of Three-Dimensional Graphene Supported CoP Nanoparticle-Embedded N-Doped Carbon as a Superior Hydrogen Evolution Catalyst

Abstract

Hydrogen evolution catalysts with effectively integrated structures at different length scales are promising to remarkably boost the efficiency of the hydrogen evolution reaction (HER), but their fabrication presents great challenges. A 3-D structure of graphene oxide (GO) conformally coated with 2,2′-biquinoline-4,4′-dicarboxylate (BQ)-Co2+ complexes is synthesized via polyvinylpyrrolidone (PVP)-mediated in situ self-assembly, in which PVP promotes attachment of BQ and Co2+ and prevents the restacking of nanosheets, while formation of amorphous BQ-Co2+ complexes allows their uniform growth. This structure is subsequently converted to 3-D graphene supported CoP NP-embedded N-doped carbon via calcination and low-temperature phosphidation and applied as a catalyst toward the HER. The onset overpotential, overpotenitial at 10 mA cm-2, Tafel slope, and exchange current density of this catalyst are 6.3 mV, 78.0 mV, 45.7 mV dec-1, and 0.3126 mA cm-2 (0.5 M H2SO4), respectively, all of which compare favorably to those of most reported non-noble-metal-based catalysts, and the catalyst displays superior durability with a slight current increase after 23 h of chronoamperometric measurement or little current loss after 2000 CV cycles. This work develops a strategy to fabricate high-performance and low-cost HER catalysts and deepens the understanding of the mechanism of the polymer-mediated in situ self-assembly of amorphous metal-organic complexes.