In Situ Integrated Co3W−WN Hybrid Nanostructure as an Efficient Bifunctional Electrocatalyst by Accelerating Water Dissociation and Enhancing Oxygen Evolution

Graphical In the hybrid Co 3 W−WN catalyst , the tungsten cobalt alloy not only acts as a water-dissociation promoter to accelerate the Volmer step, thus improving the HER activity, but also transforms in situ into OER active species to facilitate the water-oxidation process. So, the Co 3 W−WN hybrid electrocatalyst exhibits enhanced HER and OER activities with overpotentials of 43 and 273 mV, respectively, at 10 mA cm −2 . Due to the difference of catalytic mechanisms, the design of an efficient alkaline bifunctional catalyst not only needs to organically integrate different active sites, but also has to simultaneously optimize the catalytic activity of both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Here, we propose a strategy of killing two birds with one stone to construct the efficient bifunctional electrocatalyst by simultaneously accelerating water dissociation and enhancing oxygen evolution. The self-supported tungsten nitride nanowires decorated with tungsten cobalt alloy nanoparticles (Co 3 W/WN/CC) were synthesized on the flexible carbon cloth. Co 3 W can act as both a water dissociation promoter to enhance HER activity and OER active species to facilitate water oxidation via in situ transformation, thus effectively improving the overall water splitting performance. As expected, compared with pure tungsten nitride catalysts, the hybrid electrocatalyst not only shows enhanced HER activity with an overpotential decrease from 255 to 43 mV, but also achieves an excellent OER performance with overpotential of 273 mV in 1 M KOH aqueous solution. Furthermore, by employing Co 3 W/WN/CC as cathode and anode, the overall water splitting process needs 1.582 V to drive a current density of 10 mA cm −2 and maintains without decay for 80 hours. This work expands the effective strategy for building efficient, stable and low-cost alkaline bifunctional electrocatalysts.