Activating Iron Based Materials for Overall Electrochemical Water Splitting via the Incorporation of Noble Metals

Although the presence of iron in mixed metal oxide based catalysts has shown significant performance improvement in the oxygen evolution reaction (OER), iron oxides themselves demonstrate much poorer activity. In this study, we investigate improving the performance of iron catalysts via surface decoration with gold or platinum for not only the OER but also the hydrogen evolution reaction (HER) for overall water splitting in an alkaline electrolyte. Two types of iron catalysts were synthesised, iron nanocubes and iron oxide via electrochemical deposition methods which were decorated with either Au or Pt via galvanic replacement. It was found that the presence of Au significantly enhanced the OER performance of iron oxide and the HER performance of iron nanocubes. The presence of Pt resulted in moderate improvement in the OER but significant improvement for the HER but did not surpass the performance of gold decorated iron nanocubes. This indicates that the speciation of the iron catalyst and the decorating metal was important for tuning the activity to the OER and the HER. For the OER, the formation of iron oxide/Au interfaces was determined to be an important component for high activity whereas the metallic nature of metal decorated iron nanocubes was important for the HER. Therefore, iron based catalysts can be modified to demonstrate bifunctional behaviour for overall water splitting via the inclusion of gold nanoparticles.