Co₂P/MnP Nanoarrays Loaded on Coal-Based Carbon Nanofibers Serve as Effective Bifunctional Catalysts for Overall Water Splitting

Transition metal phosphides (TMPs) exhibit excellent catalytic activity in the field of electrocatalysis and are considered to be promising electrocatalysts. In this study, CoMn layered double hydroxide (CoMn-LDH) was first prepared on coal-based carbon nanofibers (C–CNFs) by a hydrothermal method. Then, using CoMn-LDH@C–CNFs as a self-sacrificing template, the CoMn Prussian blue analogue (CoMn PBA) was grown in situ. Finally, through low-temperature phosphating treatment, Co2P/MnP hierarchical nanoarrays (Co2P/MnP@C–CNFs) were successfully synthesized on C–CNFs. Benefiting from this hierarchical nanoarray structure and the synergistic effect between the highly conductive C–CNFs substrate and the phosphides, Co2P/MnP@C–CNFs exhibit highly efficient bifunctional electrocatalytic activity in a 1.0 M KOH solution. At 10 mA cm–2, the overpotential of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is 96 and 180 mV, respectively. In addition, it only requires a voltage of 1.58 V to achieve an overall water splitting of 10 mA cm–2 and can operate stably for 160 h at 10 mA cm–2. This work provides a promising approach for the preparation of transition-metal-based electrocatalysts with the fractional structure of Prussian blue analogues.