Effect of annealing and nanostructuring on pulsed laser deposited WS2 for HER catalysis

Replacement of platinum with cheap and abundant materials is a key step to enable the large scale application of water splitting schemes to produce hydrogen. Tungsten disulfide, a metal dichalcogenide showing catalytic activity toward the hydrogen evolution reaction (HER), is rapidly emerging as a cost effective alternative. In this paper we report the synthesis of WS2 thin films with pulsed laser deposition (PLD), a versatile technique which combined with thermal treatments allows us to investigate the correlation between key material properties, such as crystallinity and morphology, with HER catalysis performance. Following FESEM, XRD, Raman and electrochemical characterization, we link increased activity with higher crystallinity, different from recently reported results for related materials such as MoS2. An annealing temperature of 500 degrees C yields a markedly low onset potential of 160 mV relative to Pt metal and the introduction of nanostructuring proves a successful strategy for current density enhancement.