Photoelectrochemical Enhancement of Graphene@WS2 Nanosheets for Water Splitting Reaction

Tungsten disulfide nanosheets were successfully prepared by one-step chemical vapor deposition using tungsten oxide and thiourea in an inert gas environment. The size of the obtained nanosheets was subsequently reduced down to below 20 nm in width and 150 nm in length using high-energy ball milling, followed by 0.5 and 1 wt% graphene loading. The corresponding vibrational and structural characterizations are consistent with the fabrication of a pure WS2 structure for neat sampling and the presence of the graphene characteristic vibration modes in graphene@WS2 compounds. Additional morphological and crystal structures were examined and confirmed by high-resolution electron microscopy. Subsequently, the investigations of the optical properties evidenced the high optical absorption (98%) and lower band gap (1.75 eV) for the graphene@WS2 compared to the other samples, with good band-edge alignment to water-splitting reaction. In addition, the photoelectrochemical measurements revealed that the graphene@WS2 (1 wt%) exhibits an excellent photocurrent density (95 mu A/cm(2) at 1.23 V bias) compared with RHE and higher applied bias potential efficiency under standard simulated solar illumination AM1.5G. Precisely, graphene@WS2 (1 wt%) exhibits 3.3 times higher performance compared to pristine WS2 and higher charge transfer ability, as measured by electrical impedance spectroscopy, suggesting its potential use as an efficient photoanode for hydrogen evolution reaction.

Automated summary

In this study, tungsten disulfide (WS2) nanosheets were synthesized via one-step chemical vapor deposition and further reduced in size through high-energy ball milling with the addition of graphene. The resulting graphene@WS2 samples exhibited high optical absorption and a lower band gap compared to other samples, demonstrating good band-edge alignment with the water-splitting reaction. Additional characterization using high-resolution electron microscopy confirmed the morphology and crystal structure of the samples. Photoelectrochemical measurements revealed that the graphene@WS2 (1 wt%) sample exhibited excellent photocurrent density and higher charge transfer ability compared to pristine WS2, indicating its potential as an efficient photoanode for the hydrogen evolution reaction.