Cobalt-embedded in ultrahigh boron and nitrogen codoped hierarchically porous carbon nanowires as excellent catalysts toward water splitting

The ultrahigh boron and nitrogen doping amounts (especially the electrochemically active B/N species) boost the full water splitting electrocatalytic efficiency of three-dimensional cobalt nanoparticles embedded hierarchically porous carbon nanowires in alkaline solution. [Display omitted] •The novel Co nanoparticles embedded B/N codoped 3D hierarchically porous Co@BNPCFs.•The ultrahigh B (6.86 atom %) and N (6.59 atom %) doping amounts of Co@BNPCFs-800.•The HER Eonset and E10 values of Co@BNPCFs-800 are just 22.9 and 82.4 mV more negative than 20 wt% Pt/C.•The OER Eonset and E10 values of Co@BNPCFs-800 are 5.0 and 2.0 mV more negative than RuO2.•A low voltage of 1.596 V at 10 mA cm−2 for Co@BNPCFs-800||Co@BNPCFs-800 is 19 mV smaller than 1.615 V of 20 wt% Pt/C||RuO2. The low heteroatoms doping amount and uncontrollable formation of electrochemically inactive boron (B)–nitrogen (N) bonds have hindered the electrocatalytic activities of B and N codoped carbonaceous catalysts. Herein, the novel three-dimensional (3D) cobalt (Co) nanoparticles (NPs)-embedded and ultrahigh B and N doped hierarchically porous carbon nanowires (denoted as Co@BNPCFs) have been successfully synthesized via pyrolyzing the 3D cobalt acetate/hydroxybenzeneboronic acid/polyvinylpyrrolidone precursor networks woven by electrospinning. After optimizing the pyrolysis temperatures, the optimal Co@BNPCFs-800 owns a large surface area and abundant carbon edges/defects. Especially, 6.86 atom % of B and 6.59 atom % of N atoms are doped into carbon frameworks with affording 13.45 atom % of B/N active centers (i.e. BC3, pyridinic-N, Co-Nx-C, pyrrolic-N, and graphitic-N). In alkaline solution, the hydrogen evolution reaction overpotential at 10 mA cm−2 of the optimal Co@BNPCFs-800 (151.3 mV) is just 82.4 mV larger than 20 wt% Pt/C (68.9 mV). Especially, the oxygen evolution reaction potential at 10 mA cm−2 of the optimal Co@BNPCFs-800 (1.554 V vs. RHE) is even 2 mV more negative than RuO2 (1.556 V vs. RHE). For full water splitting, Co@BNPCFs-800 based electrolysis cell just requires a small voltage of 1.596 V to achieve 10 mA cm−2, which is 19 mV smaller than that of the state-of-the-art 20 wt% Pt/C||RuO2 benchmark (1.615 V). The perfect 3D hierarchically porous structures and fairly abundant electrocatalytic active sites dispersed along Co@BNPCFs-800′s surface are responsible for the outstanding water splitting performances. In addition, as the good structural and chemical stabilities, Co@BNPC