Effects of alkali ion on boosting WO3 photoelectrochemical performance by electrochemical doping.

Electrochemical doping is a promising method to modify the photoelectrochemical performance of semiconductors. The published works using H ions as compensated cations have shown increased photocurrents, but theories vary about the causes of the improvement of photoelectrochemical performance. In this paper, we present the effects of cation ion and the key factors of enhancement using alkali sulfates ((Li/Na/K) 2 SO 4) as the electrolyte for electrochemical doping. The effective electrode surface area (ECSA) was increased for the WO 3 film after electrochemical doping. The Li-ion, with the smallest radius and thereby the highest potential to insert into the WO 3 cell, results in the Li ion inserted WO 3 with the highest photocurrent in the three electrochemically doped samples. To investigate the possible factors affecting the photoelectrochemical performance, the electrochemically doped samples and a control sample were annealed under inert gas (Ar). The lower photocurrents were observed for the electrochemically doped samples after annealing, confirming that the key factors are the increase of the effective electrode surface area caused by electrochemical doping and ion compensation, rather than the ions themselves and the chemical bonds between alkali ions and W or O. Image 1 • Electrochemical doping was performed for WO 3 particle based film. • Enhanced photoelectrochemical activity was gained after treatment. • The effect of cations for electrochemical doping was studied. • Inserted model (Li) shows better performance than the absorption model (K) or complex model (Na). [ABSTRACT FROM AUTHOR]