Mesoporous Ni-Pt nanoparticles on Ni foam by electrodeposition: Dual porosity for efficient alkaline hydrogen evolution

In order to maximise electrochemically active surface area for water splitting, mesoporous Ni-Pt nanoparticles (NPs) are electrodeposited onto open-cell Ni foam to obtain a dual (macro- and meso-) porosity. Homogeneous deposition of the NPs is achieved by the use of a cylindrical Pt-coated mesh counter electrode, establishing a uniform electric field around the Ni foam substrate during electrodeposition. The Ni/Pt ratio is tunable with the electrodeposition parameters and all NPs are single-phase face-centred cubic solid solution and nanocrystalline, with a pore size of approx. 10 nm. Ni foam decorated with the Ni-rich particles, with mean particle sizes ranging from 50 to 80 nm, shows significantly higher activity at hydrogen evolution reaction (HER) in alkaline media with respect to the bare Ni foam. The highest HER efficiency was found fora relatively low Pt content of the NPs of about 26 at% (i. e., at 74 at% Ni) with an improvement of a factor 8 over bare Ni foam after durability assessment. These improvements are attributed to the higher surface area thanks to the NP structure, the dual porosity, and the alloying with Pt.