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 (CoTiO 3 ) 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 CoTiO 3 . We further show the application of this diagram toward the interpretation of the electrochemical behavior of nanostructured CoTiO 3 for electrochemical water splitting reactions and the electrochemical CO 2 reduction reaction (eCO 2 RR). Conclusion:The presented electrochemical and photoelectrochemical studies demonstrate nanostructured CoTiO 3 as an effective catalyst for electrochemical water oxidation and the eCO 2 RR. Moreover, our results provide valuable information for further investigation of water splitting and photovoltaic energy conversion.

A comparison between 2D and 3D cobalt–organic framework as catalysts for electrochemical CO2 reduction

“…After the characterization of the prepared samples, they were investigated for electrochemical reduction of CO 2 , a process that happens in negative potentials where cobalt nodes in ZIF-67 have already been reduced in alkaline solution via [ 52 ]: …”

“…From the mechanistic viewpoint, the first step in HER is cleaving the O–H bond of adsorbed water molecules [ 52 , 70 ], here on the cobalt nodes of ZIF-67 (Co–ZIF), which is called the Volmer step with a Tafel slope of 120 mV dec −1 : and after that, HER occurs either via the reaction between another water molecule with an adsorbed hydrogen atom (Hyrovsky step) with a Tafel slope of 40 mV dec −1 : or via the reaction between two adsorbed hydrogen atoms (Tafel step) with a Tafel slope of 30 mV dec −1 : …”

Hyperaccumulating Plants: An Emerging Avenue in Electrocatalytic Water Splitting

“…The metals these plants accumulate are precisely the catalysts needed for efficient water splitting. Nickel, for instance, is a crucial component of the hydrogen-evolving reaction, while cobalt and iron are essential for the oxygen-evolving reaction [7][8][9]. By harnessing these naturally accumulated metals, researchers are unlocking a pathway to more efficient and sustainable hydrogen production.…”