Tungsten based electrocatalysts as non-noble alternatives to common platinum based fuel cell catalysts

摘要

Today fuel cells are far from being common place in the commercial market, primarily due to their high cost. The cost of such a system is largely determined by the platinum based catalysts used at both the anode and cathode of the fuel cell. If a non-noble fuel cell electrocatalyst could be used at either of these electrodes, the cost of a fuel cell system would be drastically reduced. Highthroughput physical vapour deposition and the modification of single crystal surfaces, has been used to synthesise candidate non-noble electrocatalysts which were then screened to determine their activity.Amorphous tungsten carbide thin films were shown to be catalytically active towards both the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR). The constituent elements were seen to be less active than the alloys. These results are consistent with the literature where it has also been seen that WC is active, with W2C showing poorer activity.1,2 The trend in current density with respect to alloy composition confirms the results in the literature, with the highest activity seen at compositions corresponding to the WC phase, and a local minima in activity seen at compositions correspondingto the W2C phase.Metastable and amorphous intertransition metal alloys of WCu are shown to catalyse both the HER and the HOR. The constituent metals again exhibit poor activity. The results are consistent with ab initio calculations predicting HER activity for Cu overlayers on W, with the detected changes of the density of states (DOS) at the Fermi level associated with alloy formation.3 Two maxima in the HER activity are observed as a function of composition. This activity is associated with a metastable phase at W20Cu80 and a second at W50Cu50. The alloy at 50 at% also shows a maximum in the HOR activity, whereas the phase at W20Cu80 is not HOR active. The W20Cu80 phase is found to beoxygen covered at the HOR potential, explaining its inactivity. These results highlight the potentials of developing non-noble metal alloy catalysts for hydrogen fuel cells.