Band Structures Of Photocatalysts Research Articles

Deciphering the Superior Electronic Transmission Induced by the Li-N Ligand Pairs Boosted Photocatalytic Hydrogen Evolution.

Atomic level decoration route is designated as one of the attractive methods to regulate both the charge density and band structure of photocatalysts. Moreover, to enable more efficient separation and transport of photocarriers, the construction of novel active sites can enhance both the reactivity and electrical conductivity of the crystal. Herein, an Li-N ligand is constructed via co-doping lithium and nitrogen atoms into ZnIn2 S4 lattice, which achieves a promoted photocatalytic H2 evolution at 9737µmol g-1 h-1 . The existence of Li-N ligand pairs and the behaviors of photocarriers on L40 N5 ZIS are determined systematically, which also provides a unique insight into the mechanism of the improved photocarrier migration rate. With the introduction of Li-N dual sites, the vacancy form of ZnIn2 S4 has changed and the photocatalytic stability is significantly improved. Interestingly, the change of charge density around Li-N ligand in ZnIn2 S4 is determined by theoretical simulations, as well as the regulated energy barrier of photocatalytic water splitting caused by Li-N dual sites, which act as both adsorption site for H2 O and stronger reactive sites. This work helps to extend the understanding of ZnIn2 S4 and offers a fresh perspective for the creation of a Li-N co-doped photocatalyst.

High-efficiency photocatalytic decomposition of toluene over defective InOOH: Promotive role of oxygen vacancies in ring opening process

The potential of oxygen vacancies (OVs) has been demonstrated in controlling photocatalytic activities by altering the electronic and/or band structures of photocatalysts. The effects of oxygen vacancies on photocatalytic reaction processes are yet unclear. In this work, indium oxyhydroxide (InOOH), well known as a wide band p-block metal compound with OVs, was synthesized through a one-pot solvothermal method to explore the roles of OVs in photocatalytic oxidation and ring opening of toluene. The defect level introduced by OVs enhanced light absorption and charge carrier separation, while promoting the activation of reactants to generate active oxygen species. As such, the modified InOOH was validated to enhance the photocatalytic performance by lowering the reaction energy barrier of the key intermediates during toluene oxidation (relative to the pristine InOOH). More strikingly, the energy barrier for the formation of benzoic acid was reduced with the increasing number of OVs on InOOH (accompanied by the increases in the ring opening reaction rates), in line with the results derived from the in situ DRIFTS investigation and theoretical calculation. Accordingly, it is possible to explain the mechanism regulating the photocatalytic oxidation of toluene on defective InOOH. This work could provide an electronic insight into oxygen vacancy engineering as a new strategy to enhance the photocatalytic selectivity and activity for VOC degradation.

A Covalent Triazine-Based Framework Consisting of Donor-Acceptor Dyads for Visible-Light-Driven Photocatalytic CO2 Reduction.

Photocatalytic conversion of CO2 into value-added chemical fuels is a promising approach to address the depletion of fossil energy and environment-related concerns. Tailor-making the electronic properties and band structures of photocatalysts is pivotal to improve their efficiency and selectivity in photocatalytic CO2 reduction. Herein, a covalent triazine-based framework was developed containing electron-donor triphenylamine and electron-acceptor triazine components (DA-CTF). The engineered π-conjugated electron donor-acceptor dyads in DA-CTF not only optimized the optical bandgap but also contributed to visible-light harvesting and migration of photoexcited charge carriers. The activity of photocatalytic CO2 reduction under visible light was significantly improved compared with that of traditional g-C3 N4 and reported covalent triazine-based frameworks. This study provides molecular-level insights into the mechanism of photocatalytic CO2 reduction.

Product selectivity of photocatalytic CO2 reduction reactions

Photocatalytic carbon dioxide (CO 2 ) reduction to obtain hydrocarbon solar fuels is one of the promising strategies to solve energy crisis and complement carbon cycle. However, the low activity and poor product selectivity greatly limit its practical application. Tuning product selectivity is of great significance to improve the yield of target product and deepen the understanding of CO 2 reduction reaction mechanism. In this review, we firstly summarize the widely accepted pathways of photocatalytic CO 2 reduction reactions. Secondly, important factors affecting product selectivity are analyzed, mainly including light-excitation attributes, band structure of photocatalysts, separation of photogenerated charge carriers, adsorption/activation of reactants, surface active sites of catalytic reaction, and adsorption/desorption of intermediates. Finally, the challenges and perspectives in developing photocatalysts with high CO 2 reduction efficiency and product selectivity are presented.

Adjusting the Reduction Potential of Electrons by Quantum Confinement for Selective Photoreduction of CO2 to Methanol

The production of CH3 OH from the photocatalytic CO2 reduction reaction (PCRR) presents a promising route for the clean utilization of renewable resources, but charge recombination, an unsatisfying stability and a poor selectivity limit its practical application. In this paper, we present the design and fabrication of 0D/2D materials with polymeric C3 N4 nanosheets and CdSe quantum dots (QDs) to enhance the separation and reduce the diffusion length of charge carriers. The rapid outflow of carriers also restrains self-corrosion and consequently enhances the stability. Furthermore, based on quantum confinement effects of the QDs, the energy of the electrons could be adjusted to a level that inhibits the hydrogen evolution reaction (HER, the main competitive reaction to PCRR) and improves the selectivity and activity for CH3 OH production from the PCRR. The band structures of photocatalysts with various CdSe particle sizes were also investigated quantitatively to establish the relationship between the band energy and the photocatalytic performance.

Adjusting the Reduction Potential of Electrons by Quantum Confinement for Selective Photoreduction of CO2 to Methanol

AbstractThe production of CH3OH from the photocatalytic CO2 reduction reaction (PCRR) presents a promising route for the clean utilization of renewable resources, but charge recombination, an unsatisfying stability and a poor selectivity limit its practical application. In this paper, we present the design and fabrication of 0D/2D materials with polymeric C3N4 nanosheets and CdSe quantum dots (QDs) to enhance the separation and reduce the diffusion length of charge carriers. The rapid outflow of carriers also restrains self‐corrosion and consequently enhances the stability. Furthermore, based on quantum confinement effects of the QDs, the energy of the electrons could be adjusted to a level that inhibits the hydrogen evolution reaction (HER, the main competitive reaction to PCRR) and improves the selectivity and activity for CH3OH production from the PCRR. The band structures of photocatalysts with various CdSe particle sizes were also investigated quantitatively to establish the relationship between the band energy and the photocatalytic performance.