Carbide-directed enhancement of electrochemical hydrogen evolution reaction on tungsten carbide–oxide heterostructure

Abstract

Carbide–oxide heterointerfaces have been known to be responsible for electrochemical activity, however, it is rarely investigated in tungsten carbide-oxide heterostructure for the hydrogen evolution reaction (HER). Furthermore, typical carbide preparation includes carbonization of oxide under gaseous carbon sources at a high temperature, resulting in sintering and collapse of the heterostructures. In this work, nano-sized carbon dots (CDs, ∼2 nm in diameter) were adopted as carbon sources and dispersed on tungsten oxide nanorods allowing abundant nucleation sites for oxide-to-carbide conversion, resulting in high density of carbide-oxide heterointerfaces. The resulting tungsten carbide-oxide heterostructure decorated with carbon dots (WO(3−x) − WCy/CDs) exhibited superior electrocatalytic activity toward the HER with a low overpotential of 65 mV at a current density of − 10 mA cm−2 in acidic media. This performance is among the best electrocatalytic activities compared to the state-of-the-art tungsten carbide-based electrocatalysts. Importantly, the single-cell test using WO(3−x) − WCy/CDs as the cathode showed a current density of 10 mA cm−2 with a cell voltage of only 1.47 V, which is very close to that for Pt/C (1.41 V). In addition, a combined analysis of the X-ray spectroscopic and electrochemical results suggested an optimal W–C ratio in the tungsten carbide-oxide composite to guarantee the high HER activity. Theoretical calculations provided more insight into the carbide-directed enhancement of the electrocatalytic activity of WO(3−x) − WCy/CDs.