Electrodeposited tungsten alloys containing nickel are well-known electrocatalysts for the hydrogen evolution reaction (HER), with the added benefit of being corrosion resistant.¹ The addition of nano-scale, solid oxide particles in the deposit could serve as a potential strategy to further improve the electrocatalytic properties. In the present study, Ni-W-TiO₂ composites were fabricated by electrodeposition with different loadings of TiO₂ nanoparticles in the electrolyte. The influence of (1) the titania particles in the electrodeposition electrolyte on the hydrogen evolution side reaction and the metal partial current densities are assessed, and (2) the embedded titania particles in Ni-W on the HER kinetics in an alkaline electrolyte are also examined.

Electrodeposition

A citrate-boric acid electrolyte was used to deposit Ni-W alloys and Ni-W-TiO₂ composites onto rotating cylinder electrodes, at a pH of 8. The partial current density ratio of Ni/W was affected by the amount of particles in the electrolyte, explained, in part, by differences in adsorption that governs the metal ion induced codeposition mechanism. The hydrogen evolution side reaction was enhanced during deposition when particles were present.

HER Electrocatalysis

HER kinetic parameters of the electrodeposited Ni-W-TiO₂ composites and their alloy counterparts, were examined in 1 M NaOH. The embedded TiO₂ improved the HER Tafel slope of the electrocatalyst. To compare the overpotential and the exchange current density the electroactive surface area was characterized using a ferricyanide electrolyte with cyclic voltammetry. Under comparable surface areas and metal composition ratio, there was an improvement in lowering the overpotential with the composites but there was no change in the exchange current density. The addition of TiO₂ to a Ni-W matrix to enhance HER serves as a model system that can be adapted to other alloy electrocatalysts.

In both electrodeposition and electrocatalysis, the TiO₂ is suspected of altering the adsorption of reaction intermediates.

Reference

1. Tsyntsaru, H. Cesiulis, M. Donten, J. Sorte, E. Pellicer, and E. J. Podlaha-Murphy, Surface Engineering and Applied Electrochemistry, 48 491 (2012).