Independently enhanced ethanol detection using photocurrent on higher surface electron density of rutile black TiO2

• Black TiO 2 exhibited superior ethanol sensitivity; UV raises the response by ∼20 % at room temperature. • Gas sensing is governed by oxygen vacancies (O V s) and reduced Ti states (Ti³⁺). • Weakened Ti–O bonding enhances photocurrent and interfacial charge transfer, boosting ethanol response. TiO 2 generates charge carriers under light irradiation, which are transported to chemical molecules to drive catalytic reactions or serve as signals for detecting hazardous chemicals. Considering the higher light absorption, improved charge-carrier separation, and suppressed recombination, leading to photocurrent generation, black TiO 2 , with a higher concentration of oxygen vacancies in the rutile phase, has been proposed as a promising candidate. In this work, we applied black TiO 2 to chemiresistive gas sensing, achieving not only a higher gas response at room temperature but also exclusively enhanced ethanol sensitivity under UV illumination. Increasing oxygen-vacancy concentration and reduced-valence Ti (e.g., Ti³⁺) progressively convert pristine white TiO 2 into yellow and black forms, which correlates with enhanced gas detection. Under UV illumination, the ethanol response of black TiO 2 increases by ∼20 % relative to the no-UV condition, consistent with a photocurrent-assisted mechanism. These results demonstrate that higher UV-active black TiO 2 suggests that UV-active black TiO 2 facilitates ethanol adsorption/detection via weakened Ti–O bonding. Regarding the higher physisorption contribution for room temperature operational gas sensing, modulating surface electron density from O V , reduced Ti cation ratio and photocurrent on chromatic TiO 2 is possible to provide platforms for low temperature operable chemical application.