Engineered CO2 conversion performance of nanostructured TiO2 photocatalysts via electrochemical hydrogenation

Abstract

Modification of TiO₂ by the hydrogenation process is one of the promising ways to achieve favorable properties for efficient photocatalytic CO₂ conversion but typical chemical hydrogenation methods such as H₂ thermal treatment and the use of hydrides are not easy to control for practical application. Moreover, the study on the applications to photocatalytic CO₂ conversion by using electrochemically hydrogenated TiO₂ nanotubes (TNTs) has not been fully implemented. In this work, we demonstrate the fabrication of hydrogenated TiO₂ nanotubes (TNTs) via an electrochemical method for photocatalytic CO₂ conversion. The hydrogenated TNT surface is well-controlled in a few nm regime, with varied reaction voltages. The hydrogenated TNT photocatalysts display a remarkable production rate of 0.57 μmol cm⁻² h⁻¹ (= ca. 297 μmol g⁻¹ h⁻¹) of CH₄, which is four times higher than that by bare TNT. These significantly enhanced photocatalytic performances are attributed to the synergistic effects of hydrogenated nanostructures of the TiO₂ surface, which represent enhanced light absorption, highly ordered nanostructures, and improved electrical properties due to the electrochemical hydrogenation.