Self-supporting honeycomb coaxial carbon fibers: A new strategy to achieve an efficient hydrogen evolution reaction both in base and acid media

The electrocatalytic reaction mainly occurs on the surface of the electrocatalyst, while the active substances inside the electrocatalyst do not participate in the catalytic reaction. Therefore, core layer electrocatalysts with coaxial structures face lower utilization rates and a significant decrease in the number of exposed active sites, which in turn affects the electrocatalytic activity. Here, a novel one-dimensional (1D) honeycomb coaxial carbon nanofibers with MoC shell and Ni core layer (denoted as [Ni/C]@[MoC/C]-PCNFs) have been successfully prepared by pyrolysis of coaxial precursors fibers of [Ni(acac)2/PAN/PS]@[MoO2(acac)2/PAN]. The core layer of [Ni/C]@[MoC/C]-PCNFs) has a multi-channel honeycomb-like structure due to the pyrolysis of PS. The specific surface area of [Ni/C]@[MoC/C]-PCNFs (143.1 m2g−1) is more than twice that of the coaxial fibers with solid core structures (denoted as [Ni/C]@[MoC/C]-CNFs, 60.2 m2g−1). Simultaneously, the heterostructure formed between MoC and Ni, allowing for the adjustment of the electronic structure, acceleration of electron transfer and optimization of the electrocatalytic HER performance. The optimized self-supporting [Ni/C]@[MoC/C]-PCNFs exhibit the best catalytic activity for HER in both alkaline and acidic solutions, requiring only 84 and 160 mV to drive a current density of 10 mA cm−2. In addition, [Ni/C]@[MoC/C]-PCNFs catalyst exhibits good stability in both acidic and alkaline electrolytes. This core layer multi-channel coaxial structure designing provides an effective strategy for improving the electrocatalytic performance of catalysts.