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

Abstract

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. Spectroelectrochemical 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.