Ultrafine Metal Nanoparticles/N-Doped Porous Carbon Hybrids Coated on Carbon Fibers as Flexible and Binder-Free Water Splitting Catalysts

By employing in situ reduction of metal precursor and metal-assisted carbon etching process, this study achieves a series of ultrafine transition metal-based nanoparticles (Ni–Fe, Ni–Mo) embedded in N-doped carbon, which are found efficient catalysts for electrolytic water splitting. The as-prepared hybrid materials demonstrate outstanding catalytic activities as non-noble metal electrodes rendered by the synergistic effect of bimetal elements and N-dopants, the improved electrical conductivity, and hydrophilism. Ni/Mo₂C@N-doped porous carbon (NiMo-polyvinylpyrrolidone (PVP)) and NiFe@N-doped carbon (NiFe-PVP) produce low overpotentials of 130 and 297 mV at a current density of 10 mA cm⁻² as catalysts for hydrogen evolution reaction and oxygen evolution reaction, respectively. In addition, these binder-free electrodes show long-term stability. Overall water splitting is also demonstrated based on the couple of NiMo-PVP||NiFe-PVP catalyzer. This represents a simple and effective synthesis method toward a new type of nanometal–carbon hybrid electrodes.