Size-controllable Rh2P nanoparticles on reduced graphene oxide toward highly hydrogen production

[Display omitted] •One-step synthesis of Rh2P/RGO composite is demonstrated.•The GO may be lead to the controllable size and uniform distribution of Rh2P NPs.•A moderate ΔGH-ad and accelerated electron transport at Rh2P/RGO enhance HER.•Rh2P/RGO only needs 11.7 and 10.3 mV at η10 in 0.5 M H2SO4 and 1 M KOH for HER. Abundant of defective regions and oxygen-containing groups on graphene oxide (GO) could promote the nucleation and growth of metallic nanoparticles. In this work, the composite catalyst is synthesized by pyrolysis of the mixture powder of GO and rhodium organometallic reactant at 900 °C, Ar atmosphere and low pressure, in which dispersive Rh2P nanoparticles are uniformly attached on reduced graphene oxide (Rh2P/RGO). The sizes of Rh2P nanoparticles are controllable by adjusting the mass proportion of reactants. For the optimized size of Rh2P nanoparticles at 6.0 nm, only 11.7 and 10.3 mV of the overpotentials are required at the current density of 10 mA cm−2 in 0.5 M H2SO4 and 1 M KOH electrolytes, respectively, exhibiting superior HER activity over the commercial Pt/C. Theoretical calculations indicate that the hydrogen adsorption free energy of Rh2P/RGO composites is close to zero, and Bede charge analysis confirms the accelerated electron transport between the RGO and Rh2P. Therefore, the introduction of RGO substrate could not only promote a uniform distribution and tunable size of Rh2P NPs, but also be advantageous to the electron transport from RGO to Rh2P NPs, and a favorable H2 evolution during the HER process. This work provides a facile strategy to control the size of metal phosphide nanoparticles on RGO for the design of advanced HER electrocatalysts.