The shape-controlled synthesis of gallium–palladium (GaPd2) nanomaterials as high-performance electrocatalysts for the hydrogen evolution reaction

Abstract

Recently, great efforts have been focused on developing more active and stable Pd-based electrocatalysts to partially or completely replace rare and costly Pt. We developed a facile hot injection method and successfully synthesized well-dispersed and shape-controlled GaPd₂ nanomaterials including polyhedrons, nanoparticles and nanowires. All the as-synthesized catalysts exhibit superior HER activity compared to commercial pure Pd catalysts and are stable in acidic media. Among them, the GaPd₂ nanoparticles required only 24.3 mV overpotential to achieve a 10 mA cm⁻² current density, which is outstanding compared to most Pt-based nanomaterials. Also, cycling tests over 10 000 CV sweep cycles (−0.3 to 0.2 vs. RHE) and durability testing for 24 hours were applied, with the GaPd₂ catalysts exhibiting similar i–V curves and stable current densities to those obtained in the initial tests. We further evaluated the mass activities of the GaPd₂ catalysts, and it is fascinating that the GaPd₂ polyhedrons, nanoparticles and nanowires achieved factors of 3.7, 5 and 2.3 enhancement in mass activity at −0.1 V vs. RHE compared with a commercial Pd black catalyst. Meanwhile, with the assistance of a reduced graphene oxide (rGO) support, the GaPd₂ nanoparticles/rGO (20 wt%) electrocatalyst presents outstanding HER activity comparable with that of a carbon-supported Pt catalyst (20% Pt/C). This work provides an avenue to develop effective and stable Pd-based catalysts with reduced Pd usage and high HER performance.