Earth-abundant layered tungsten disulfide (WS2 ) is a well-known electrocatalyst for acidic hydrogen evolution, but it becomes rather sluggish for alkaline hydrogen or oxygen evolution due to the low-density edge sites, poor conductivity, and unfavorable water dissociation behavior. Here, an interfacial engineering strategy to construct an efficient bifunctional electrocatalyst by in situ growing N-doped WS2 nanoparticles on highly conductive cobalt nitride (N-WS2 /Co3 N) for concurrent hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) is demonstrated. Benefiting from the good conductivity of Co3 N, rich well-oriented edge sites and water-dissociation sites at the nanoscale interfaces between N-WS2 and Co3 N, the resultant N-WS2 /Co3 N exhibits remarkable HER activity in 1 m potasium hydroxide (KOH) requiring a small overpotential of 67 mV at 10 mA cm-2 with outstanding long-term durability at 500 mA cm-2 , representing the best alkaline hydrogen-evolving activity among reported WS2 catalysts. In particular, this hybrid catalyst also shows exceptional catalytic activities toward theurea oxidation reaction featured by very low potentials of 1.378 and 1.41 V to deliver 100 and 500 mA cm-2 along with superb large-current stability in 1 m KOH + 0.5 m urea. Moreover, the assembled two-electrode cell delivers the industrially practical current density of 500 mA cm-2 at a low cell voltage of 1.72 V with excellent durability in alkaline urea-containing solutions, outperforming most MoS2 -like bifunctional electrocatalysts for overall water splitting reported hitherto. This work provides a promising avenue for the development of high-performance WS2 -based electrocatalysts for alkaline water splitting.
Keywords: alkaline water electrolysis; electrocatalysts; electrooxidation; hydrogen evolution reaction; tungsten disulfide.
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