Enhancing the photoelectrochemical water splitting performance of WS2 nanosheets by doping titanium and molybdenum via a low temperature CVD method

Abstract

In photoelectrochemical (PEC) water splitting, the efficiency of an electrode is determined by light absorption and charge transformation between the electrode and electrolyte. Titanium (Ti) and molybdenum (Mo) doped tungsten sulfide (WS2) nanosheets were prepared via a relatively low-temperature chemical vapor deposition (CVD) method and applied to enhance the light absorption of WS2 nanosheets as the water oxidation catalyst in the PEC water splitting process. Both Ti and Mo doping showed significant enhancement in photoelectrochemical performance of prepared WS2 nanosheets. The novel Ti-doped WS2 photoanode exhibited a high photocurrent density of 10.44 mA/cm2 at 1.23 V versus the reversible hydrogen electrode (RHE) under standard AM 1.5 G illumination, which was >100% increase compared to that of the pristine WS2 photoanode. The maximum of applied bias photon-to-current efficiency (ABPE) of Ti-doped WS2 photoanode was 2.84% that showed a 338% growth comparing to WS2 photoanode. The charge transfer resistance (Rct) of Ti-doped WS2 nanosheets was 6.3 kΩ, which corresponds about two times less than pristine WS2 nanosheets. The high donor density of Ti-doped WS2 nanosheets leads to improve electrical conductivity and confirms the lower Rct which enhancing the electrocatalytic activity and PEC performance. This work demonstrates the feasibility process for doping foreign element in the WS2 nanosheets as an excellent photoanode for PEC water splitting.