Enhanced photoelectrocatalysis in porous single crystalline rutile titanium dioxide electrodes

Abstract

Titanium dioxide (TiO₂) is an important photocatalyst in the applications of photocatalysis and energy conversion. Due to its unique physical and chemical properties as an n-type semiconductor, efforts have been made to enhance its photoelectrochemical performance through structural engineering aimed at manipulating intrinsic vacancies and titanium interstitials. Nevertheless, the rapid electron/hole recombination in photo-anodes, inducing short charge carrier lifetimes that are insufficient to sustain surface photochemical reactions, poses fundamental challenges to the research of photoelectrocatalysis. Here we grow porous single-crystalline (PSC) rutile TiO₂ with (110) facets at centimeter scale in solid–solid phase transformation, and fabricate PSC rutile Ti_nO_2n−1 with the Magnéli phase in a reducing atmosphere. The PSC rutile Ti_nO_2n−1 monolith exhibits both structural coherence and porous architecture, which effectively reduces photon scattering and carrier recombination, thereby demonstrating enhanced visible light absorption to facilitate surface catalytic reactions. Therefore, PSC rutile Ti_nO_2n−1 (n = 9, 38) provide enhanced exciton lifetime (4–7 ns) and significant visible light absorption. The PSC rutile Ti_nO_2n−1 monolith delivers a high photocurrent of 2–8 mA cm⁻² under 10 AM 1.5G illumination and maintains stability for 10 hours.