Tuning the (111)/(110) facet-area ratio of rutile TiO2 nanorods for enhanced charge separation and formaldehyde photo-oxidation

Regulating the exposed-facet area ratio of rutile TiO 2 is an effective route to tune charge separation, but its influence on gas-phase formaldehyde photo-oxidation remains unclear. Here, rutile TiO 2 nanorods with different (111)/(110) facet-area ratios were synthesized by an HCl-assisted hydrothermal route by varying the HCl concentration. Increasing the acid concentration promoted the formation of well-defined rutile nanorods, while the corresponding facet-area ratio decreased from 0.138 to 0.044 as the rods became longer and thinner. Among the samples, TNH-3M (R f = 0.138) exhibited the weakest photoluminescence, the highest photocurrent response, and the smallest electrochemical impedance arc, indicating the most efficient charge separation and interfacial charge transfer. Mott-Schottky analysis further showed that TNH-3M possessed the most positive valence-band position among the rutile nanorod samples, which favored the generation of •OH radicals. Accordingly, TNH-3M delivered complete removal of gaseous formaldehyde within 2 h under 420 nm LED irradiation and maintained >95% efficiency after repeated cycling. Batch synthesis also retained high activity, confirming the scalability of the preparation strategy. The improved performance is therefore attributed to the optimized balance between the oxidation-dominant (111) facets and reduction-dominant (110) facets, which promotes spatial charge separation and enhances ROS generation. Download: Download high-res image (171KB) Download: Download full-size image