Chemical vapor deposition of monolayer WS2 nanosheets on Au foils toward direct application in hydrogen evolution

Monolayer tungsten disulfide (WS2), a typical member of the semiconducting transition metal dichalcogenide family, has drawn considerable interest because of its unique properties. Intriguingly, the edge of WS2 exhibits an ideal hydrogen binding energy, which makes WS2 a potential alternative to Pt-based electrocatalysts for the hydrogen evolution reaction (HER). Here, we demonstrate for the first time the successful synthesis of uniform monolayer WS2 nanosheets on centimeter-scale Au foils using a facile, low-pressure chemical vapor deposition method. The edge lengths of the universally observed triangular WS2 nanosheets are tunable from ∼100 to ∼1,000 nm. The WS2 nanosheets on Au foils featuring abundant edges were then discovered to be efficient catalysts for the HER, exhibiting a rather high exchange current density of ∼30.20 μA/cm2 and a small onset potential of ∼110 mV. The effects of coverage and domain size (which correlate closely with the active edge density of WS2) on the electrocatalytic activity were investigated. This work not only provides a novel route toward the batch-production of monolayer WS2 via the introduction of metal foil substrates but also opens up its direct application for facile HER.