High bifunctional electrocatalytic activity of FeWO₄/Fe₃O₄@NrGO nanocomposites towards electrolyzer and fuel cell technologies

Electrolyzer and fuel cell technologies are tremendously considered expert solutions for storing and converting renewable energy sources. The most important electrocatalytic reactions using electrolyzers and fuel cell technologies are the hydrogen evolution reaction (HER) and the oxygen reduction reaction (ORR). The development of electrocatalysts without noble metals of high economic value for HER and ORR in alkali environments continues to be a significant challenge. Here we report a new strategy for the straightforward microwave approach of synthesizing the FeWO₄/Fe₃O₄ embedded in the electrically nitrogen-doped reduced graphene oxide nanosheets (FeWO₄/Fe₃O₄@NrGO) acting as a useful electrocatalytic converter for HER and ORR in an alkaline environment. FeWO₄/Fe₃O₄@NrGO nanocomposite displays more significant electrocatalytic activity and stability, for HER enabling a current density of 10 mA cm⁻² at a low overpotential (292 mV), and also ORR enabling a limiting current density of 5.1 mA cm⁻² at a low onset potential (0.93 V). The electrocatalytic activity of FeWO₄/Fe₃O₄@NrGO was much higher than that of NrGO, FeWO₄, Fe₃O₄, FeWO₄/Fe₃O₄, and very close to that of 20 wt% Pt/C. Such outstanding catalytic properties may be attributed to the abundant active sites and the synergy provided by the combination of FeWO₄, Fe₃O₄, and NrGO for the improved electrocatalytic performance of FeWO₄/Fe₃O₄@NrGO nanocomposite towards HER and ORR. These findings pave the way for novel graphene-metal tungstate-based nanocomposites as heavy electrode materials in electrically conductive for future energy-related applications.