Mn-Modified ZnO Nanoflakes for Optimal Photoelectrochemical Performance Under Visible Light: Experimental Design and Theoretical Rationalization

Abstract

Doping of zinc oxide (ZnO) with manganese (Mn) tunes midbandgap states of ZnO to enhance its optical properties and makes it into an efficient photoactive material for photoelectrochemical water splitting, waste removal from water, and other applications. We demonstrate that ZnO modified with 1 at. % Mn exhibits the best performance, as rationalized by experimental, structural, and optical characterization and theoretical analysis. ZnO doped with the optimal Mn content possesses improved light absorption in the visible region and minimizes charge carrier recombination. The doping is substitutional and creates midgap states near the valence band. Mn atoms break localized charge traps at oxygen vacancy sites and eliminate photoluminescence peaks associated with oxygen vacancies. The optimal performance of Mn-modified ZnO is demonstrated with the photodegradation of Congo red and photoelectrochemical water splitting.

Atomic layer deposition of Al-doped ZnO nanomembrane with in situ monitoring

“…Yet, ZnO possesses relatively low conductivity and charge concentration [10]. Introducing Al [11], Cd [12], Ga [13], Mn [14] or In [15] into ZnO film significantly enhances the film's conductivity and overall performance. Previous investigation on Al-doped ZnO (AZO) films demonstrate high transparency across the visible range [16].…”

Ferroelectric Polarization and Single-Atom Catalyst Synergistically Promoting CO2 Photoreduction of CuBiP2Se6

“…Subsequently, some researchers proposed that anchoring single-atom catalyst (SACs) on the surface of a 2D material can activate CO 2 molecules. ,− Since the transition metals have unsaturated d orbitals, which can accept the lone pair electrons from CO 2 , these electrons are then back-donated to the π* orbitals to form a bent radical CO 2 •– anion that weakens the C=O bond. In addition, SACs play an important role in improving surface chemical bonding strength, band edge positions, and reaction activation energy, which has been confirmed by previous experimental and theoretical studies. − Inspired by these recent achievements, we expect to design an advanced photocatalyst with high catalytic activity and selectivity by combining ferroelectric polarization with SACs.…”

Origin of the Improved Photoelectrochemical and Photocatalytic Activity in a ZnO-TiO2 Nanohybrid Revealed by Experimental and Density Functional Theory Studies

“…The current energy demand around the globe has intensified the research for clean and renewable energy technologies that can directly abate the continuous deterioration of the environment by achieving zero CO 2 emissions. − In this context, the utilization of solar energy for photocatalysis and photoelectrochemical (PEC) water splitting has attracted an extensive amount of research interest. − In recent times, scientists have focused on photoactive metal oxides as emerging materials owing to their low cost, facile synthesis, and long-term stability. − In the past few years, there has been an enormous amount of interest in the development of heterojunction-based composite materials, with enhanced photoactivity and redox ability. , It has been reported that the selection of materials for heterojunction formation based on their respective band edge positions is crucial to achieve favorable charge carrier dynamics. , In a typical PEC system, the hydrogen evolution reaction (HER) occurs at the photocathode [H + /H 2 at 0 V vs the reversible hydrogen electrode (RHE)], while the photoanode is responsible for the oxygen evolution reaction (OER, O 2 /H 2 O at 1.23 V vs the RHE) . Both photocatalysis and PEC water splitting involve the generation of electrons and holes under light, followed by their transport to the surface.…”

“… 1 − 5 In this context, the utilization of solar energy for photocatalysis and photoelectrochemical (PEC) water splitting has attracted an extensive amount of research interest. 6 − 9 In recent times, scientists have focused on photoactive metal oxides as emerging materials owing to their low cost, facile synthesis, and long-term stability. 10 − 12 In the past few years, there has been an enormous amount of interest in the development of heterojunction-based composite materials, with enhanced photoactivity and redox ability.…”