Revealing electronic structure of nanostructured cobalt titanate via a combination of optical and electrochemical approaches toward water splitting and CO2 reduction

Abstract

Background: The shortage of clean energy has become a serious problem due to the rapid development of societies and the increasing consumption of fossil fuels. Metal oxide semiconductor nanomaterials have been studied as photo-/electrocatalysts for water splitting in terms of clean energy generation. Applications of semiconductors depend on their electronic structures. Therefore, elucidating the electronic diagram is essential for determining the specific applications of novel semiconductors. Results: Herein, we demonstrate using a combination of UV–visible diffuse reflectance spectroscopy (DRS) and Mott–Schottky analysis via electrochemical impedance spectroscopy for sketching the electronic diagram of nanostructured cobalt titanate (CoTiO3) prepared by the sol–gel method. UV–visible DRS studies reveal a band gap of 2.5 and 2.1 eV for direct and indirect transitions of prepared nanostructured materials, respectively. Mott–Schottky analysis shows a 0.8 V versus Ag/AgCl value for the flat band potential for CoTiO3.We further show the application of this diagram toward the interpretation of the electrochemical behavior of nanostructured CoTiO3 for electrochemical water splitting reactions and the electrochemical CO2 reduction reaction (eCO2RR). Conclusion: The presented electrochemical and photoelectrochemical studies demonstrate nanostructured CoTiO3 as an effective catalyst for electrochemical water oxidation and the eCO2RR. Moreover, our results provide valuable information for further investigation of water splitting and photovoltaic energy conversion.