Tungsten Carbides as Alternative Electrocatalysts: From Surface Science Studies to Fuel Cell Evaluation

Abstract

In the current paper we will provide a review of our recent efforts in experimental studies of tungsten carbides as alternative electrocatalysts for methanol electro-oxidation. We will first discuss ultrahigh vacuum (UHV) studies on single crystal surfaces to demonstrate the feasibility of using tungsten carbides for methanol decomposition. We then discuss UHV studies on polycrystalline thin films and foils to approximate commercially relevant catalysts, thus bridging the “materials gap” and demonstrating that the fundamental chemistry observed in UHV over single crystal surfaces is applicable to morphologically complex surfaces. Electrochemical studies of thin films will be discussed to bridge the “pressure gap” and to verify that tungsten carbides are both active and stable in an electrochemical environment. Finally, we will provide performance data from direct methanol fuel cell (DMFC) testing that incorporates tungsten carbides as the anode electrocatalysts.

Core-shell structured tungsten–tungsten carbide as a Pt catalyst support and its activity for methanol electrooxidation

“…Ganesan et al [10] reported that Pt on mesoporous WC nanoparticles were more active for MOR than commercial PteRu/C catalyst. High activity of Pt/WC was confirmed in the measurements with DMFC [7] in which Pt/WC and Pt/Ru anode catalysts demonstrated similar power density calculated per mass of metal at anode, but no similar study with pure WC as the anode catalyst was reported.…”

“…Therefore, on the Pt surface in contact with tungsten oxide, full monolayer of CO ads in not achieved. This can be caused by the presence of tungsten oxides capable to oxidize a part of CO ads [7,23,26], thus preventing a full monolayer to be developed. The effect points out that CO ads stripping voltammetry is not reliable for determination of Pt surface area in Pt/W-C catalyst.…”

Recent advances in heterogeneous electrocatalysts for the hydrogen evolution reaction

“…DFT calculations have suggested that the hybridization between metal and carbon orbitals gives rise to higher electron density of states at the Fermi level and a broad unoccupied d-band, affording characteristics resembling those of the Pt metal 87,88. As a result, early transition metal carbides often exhibit Pt-like electrocatalytic activity not only for HER, but also for the oxidation of hydrogen and small organic molecules such as methanol and formic acid 89,90. In addition, it is worth noting that they are not as vulnerable as Pt to poisoning and deactivation.other carbon-containing compounds 86.…”

Core–Shell-Structured Low-Platinum Electrocatalysts for Fuel Cell Applications

“…This weaker CO binding energy can subsequently facilitate CO oxidation by using surface -OH species to produce CO 2 , and thereby increase the availability of active sites on the Pt monolayer. This has been confirmed by both DFT calculations and experimental results [509,510,[521][522][523]. However, nanosize core-shell-structured WC@ Pt catalysts for MORs have only been reported by a few groups [516,524], and in one example, Chen et al [516] synthesized core-shell WC@meso-Pt nanocatalysts through the carburization of ammonium tungstate and copper nitrate using gas-solid reactions followed by a Pt replacement (Fig.…”