Got TiO2 Nanotubes? Lithium Ion Intercalation Can Boost Their Photoelectrochemical Performance

Cations such as H+ and Li+ are intercalated into TiO2 nanotube arrays by subjecting them to short-term electrochemical pulses at controlled potentials (<-1.0 V vs Ag/AgCl). The intercalation of these small cations has a profound effect toward enhancing photocurrent generation under UV light irradiation, A nearly three-fold increase in the photoconversion efficiency (IPCE) was observed upon intercalation of Li+ ions into TiO2 nanotube arrays. The intercalation process is visualized by the color change from gray to blue. Spectro-electrochemical measurements were carried out to monitor the absorption changes at different applied potentials. The analysis of the V-oc decay following termination of UV light shows a significant decrease in the rate of recombination of accumulated electrons upon Li+ ion intercalation.