Synthesis of three-dimensional (3D) hierarchically porous iron–nickel nanoparticles encapsulated in boron and nitrogen-codoped porous carbon nanosheets for accelerated water splitting

Designing two-dimensional (2D) porous carbon nanosheets is a promising strategy for enhancing the water-splitting activities of non-noble metal catalysts. In this study, we developed a novel method for synthesizing the novel three-dimensional (3D) hierarchically porous iron-nickel (FeNi) nanoparticles encapsulated in boron (B) and nitrogen (N)-codoped porous carbon nanosheets (denoted as FeNi@BNPCNS). Owing to the advantages of morphology and structure of B and N, 10.31 atom % of B/N active centers were successfully doped into the optimal FeNi@BNPCNS-800 nanosheets. FeNi@BNPCNS-800 exhibited better hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalytic activities than control catalysts in an alkaline solution. However, the HER and OER electrocatalytic activities of FeNi@BNPCNS-800 were slightly lower than 20 wt% Pt/C and RuO2. The FeNi@BNPCNS-800||FeNi@BNPCNS-800 electrolyzer achieved 10 mA cm-2 at 1.514 V, which was 73 mV lower than that of 20 wt% Pt/C||RuO2 electrolyzer (1.587 V). The perfect 3D honeycomb-like architectures, abundant mesopores/defects, and abundant electrocatalytic active sites were attributed to the outstanding water-splitting performances of FeNi@BNPCNS-800 nanosheets. This study provides an efficient strategy for the large-scale, rapid, and low-cost fabrication of 2D porous carbon nanosheets without using any template, surfactant, or expensive raw material, thus presenting a simple approach to design advanced non-noble metal electrocatalysts for water splitting.