Nitrogen-doped iron-cobalt alloy and tungsten oxide heterostructures: active electrocatalysts for alkaline hydrogen evolution.

Hydrogen has become an ideal alternative energy carrier in response to the growing global energy crisis and the transition away from fossil fuel dependence. The development of effective, affordable and long-lasting electrocatalysts for water splitting to produce hydrogen remains a major challenge. In this work, a facile coprecipitation of nitrogen-doped FeCo alloy (FCN) nanoparticles in the presence of preformed WO3 nanostructures of various quantities resulted in nitrogen-doped FeCo/WO3-based heterostructures (FCNWO). This heterostructure engineering of electrocatalysts improves the hydrogen evolution reaction (HER) by creating interfaces that expose active sites and accelerate the charge transfer. The morphology and crystal structure of the FCNWO samples synthesised with different FCN : WO3 ratios were characterised and electrochemical hydrogen generation activity evaluated. Among them, the FCNWO-2 catalyst, prepared with a precursor FeCo : WO3 ratio of 1 : 0.75 exhibited optimal performance and demonstrated the best HER activity in 1.0 M KOH, with an overpotential of 275 mV at 10 mA cm-2, a small Tafel slope of 71 mV dec-1 and a high electrochemical surface area of 322.5 cm2. These results demonstrate its promise as an effective electrocatalyst for energy conversion and storage applications.