EXAFS Analysis of Electrocatalytic WC Materials

Abstract

Tungsten carbide is an interesting non-noble metal anode electrocatalyst that can be passivated against corrosion in acidic electrolytes for use in low-temperature fuel cells. The structure of nanocrystalline WC passivated in 1.5 M H2SO4 at 65 °C was studied using synchrotron extended X-ray absorption fine structure spectroscopy and compared with the as-prepared material. Changes in the average local structure are noted that correspond to the development of an oxide phase in the material. This is most likely to be present as a WIV-oxide phase on the surfaces of the particles.

Alloying Tungsten Carbide Nanoparticles with Tantalum: Impact on Electrochemical Oxidation Resistance and Hydrogen Evolution Activity

“…Because WC NPs have not been studied using XAS techniques, a variety of bulk micron-sized powders were used as references, including metallic W, α-WC, WO 2 , and WO 3 . We note that WO 3 is not stable under synchrotron radiation and undergoes partial reduction during analysis . Therefore, WO 3 is reported as WO 3– x in Figure .…”

“…We note that WO 3 is not stable under synchrotron radiation and undergoes partial reduction during analysis. 40 Therefore, WO 3 is reported as WO 3−x in Figure 3. A commercial bulk W 2 C powder was also analyzed, but the PXRD diffractogram shown in Figure S1 indicates that this material is actually a mixture of α-WC and W 2 C. It is therefore labeled as W 2 C-WC in Figure 3 and is included only as a qualitative reference.…”

Molybdenum and tungsten carbides can shine too

“…Since the 1970s, tungsten and molybdenum carbides have emerged as alternatives for noble metal catalysts. 23,24 From a characterisation point of view [25][26][27] and from a performance 5,28 point of view, these carbides resemble noble metals (especially Pt). For instance, in 1992, Oyama made a comparison between transition metal carbides and nitrides and noble metals.…”

Minimizing the Use of Platinum in Hydrogen‐Evolving Electrodes

“…The relatively high surface energy of WC would make small nanoparticles of the material inherently more challenging to synthesize than those of pure Pt 9. The long‐term stability of the catalyst would also need to be evaluated, especially given that WC compounds can form oxides in the harsh environment of an electrochemical cell 10…”