Tuning the composition of tri-metal iron based phosphides integrated on phosphorus-doped vertically aligned graphene arrays for enhanced electrocatalytic activity towards overall water splitting

Iron-based metal phosphides (IMPs) have emerged as a new type of bifunctional electrocatalyst for overall water splitting with high efficiency and good stability. We report IMPs nanoparticles' fabrication with different metal element compositions anchored on phosphorus-doped vertically aligned graphene arrays (IMPs/P-VG), which is successfully achieved by tuning the different phosphates in the electroless plating solution. Compared with other metal ratios of electrocatalysts , Fe 0.5 Co 1.5 Ni 0.5 P/P-VG exhibits the best apparent and intrinsic activity in 1 M KOH, and it also shows good stability up to 12 h without any significant degradation. Moreover, benefiting the unique hierarchical vertical arrays nanostructure of the substrate and the trimetallic phosphides' synergetic effects, the Faraday efficiency of the electrolytic cell based on Fe 0.5 Co 1.5 Ni 0.5 P/P-VG double electrode for the overall water-splitting is up to 90%. This study suggests that proper tuning of the composition of metal elements in IMPs and integrated on compatible substrates can effectively improve the electrocatalytic activity of IMPs for water splitting.