(702b) Synthesis of Pt-Modified Tungsten Monocarbide and Its Activity towards the Hydrogen Evolution Reaction

Hydrogen is a promising energy carrier for the future because it represents a means for carbon-free energy storage and can be produced from biomass or water using renewable energy. When produced from water in an electrolyzer or photoelectrochemical cell (PEC), H₂(g) is evolved at the cathode via the hydrogen evolution reaction (HER) while water is split at the anode to produce O₂(g). For electrolysis in acidic solutions, the best HER catalysts are precious metals such as Pt, Rh, and Pd [1], but their prohibitively high costs and limited supplies are major hurdles for the widespread production of H₂ by this means. One approach for overcoming this challenge is to disperse the active precious metal catalyst in sub-monolayer or monolayer coverages on a low-cost, stable, supporting catalyst.

In this work, we investigate the performance of tungsten monocarbide (WC), modified by sub-monolayer amounts of Pt, as a HER catalyst. WC is an attractive material for this purpose because it has shown an appreciable activity for the HER [2], is known for its electrocatalytic stability in acidic solutions [3], and has demonstrated synergistic effects when combined with Pt as an electrocatalyst [4]. In recent years, several research groups have reported high HER activity for Pt-modified tungsten carbides in acidic solutions [5],[6], but these carbides are phase mixtures of WC, WC_1-x, and W₂C. One of the goals of our research is to distinguish between the effectiveness of these various carbide phases as HER catalysts. Initial studies have investigated the activity of phase-pure WC and Pt-WC thin film electrodes for the HER in H₂SO₄. The composition and phase purity of these films has been verified using XPS and GIXRD, and their activity towards the HER investigated using linear sweep voltammetry (LSV) and chronoamperometry. The LSV measurements show a significant improvement in WC HER activity upon modification by one monolayer of Pt, and post-electrochemistry XPS measurements indicate no loss of Pt from the WC surface. Current work is focused on investigating the effect of different coverages of Pt on the HER activity of WC and its comparison to polycrystalline Pt foils.

References

[1] H. Kita, Journal of the Electrochemical Society, 113 (1966) 1095.

[2] D.V. Sokolsky, V.S. Palanker, and E.N. Baybatyrov, Electrochemica Acta, 20 (1975) 71.

[3] M.B. Zellner and J.G. Chen, Catalysis Today, 99 (2005) 299.

[4] E.C. Weigert, A.L. Stottlemyer, and J.G. Chen, Journal of Physical Chemistry C, 111 (2007) 14617.

[5] M. Wu and M. Nie, Journal of Power Sources, 166 (2007) 310.

[6] D.J. Ham, R. Ganesan, and J.S. Lee, Int. J. of Hydrogen Energy, 33 (2008) 6865.