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

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.