We have sought to improve the electrocatalytic performance of tungsten nitride through synthetic control over chemical composition and morphology.In particular,we have generated a thermodynamically unstable but catalytically promising nitrogen-rich phase of tungsten via a hydrothermal generation of a tungsten oxide intermediate and subsequent annealing in ammonia.The net product consisted of three-dimensional (3D) micron-scale flower-like motifs of W2N3;this architecture not only evinced high structural stability but also incorporated the favorable properties of constituent two-dimensional nanosheets.From a performance perspective,as-prepared 3D W2N3 demonstrated promising hydrogen evolution reaction (HER) activities,especially in an acidic environment with a measured overpotential value of-101 mV at a currant density of 10 mNcm2.To further enhance the electrocatalytic activity,small amounts of precious metal nanoparticles (such as Pt and Au),consisting of variable sizes,were uniformly deposited onto the underlying 3D W2N3 motifs using a facile direct deposition method;these composites were applied towards the CO2 reduction reaction (CO2RR).A highlight of this series of experiments was that Au/W2N3 composites were found to be a much more active HER (as opposed to either a CO2RR or a methanol oxidation reaction (MOR)) catalyst.