Intrinsic Polarized Electric Field Induces a Storing Mechanism to Achieve Energy Storing Catalysis in V2 C MXene.

Efficient storage and separation of holes and electrons pose significant challenges for catalytic reactions, particularly in the context of single-phase catalysis. Herein, V2 C MXene, with its intrinsic polarized electric field, successfully overcomes this obstacle. To enhance hole storage, a multistep etching process is employed under reducing conditions to control the content of surface termination groups, thus exposing more defective active sites. The intrinsically polarized electric field confines holes to the surface of the layer and free electrons within the layer, leading to a lag in e- release compared to h+ . The quantities of stored holes and electrons are measured to be 18.13 µmol g-1 and 106.37 µmol g-1 , respectively. Under dark, V2 C demonstrates excellent and stable dark-catalytic performance, degrading 57.91% of tetracycline (TC 40 mg L-1 ) and removing 23% of total organic carbon (TOC) after 140 min. In simulated sunlight and near-infrared light, the corresponding degradation rates reach 72.24% and 79.54%, with corresponding TOC removal rates of 49% and 48%, respectively. The hole and electron induced localized surface plasmon resonance (LSPR) effects contribute to a long-lasting and enhanced broad-spectrum mineralization of V2 C MXene. This study provides valuable insights into the research and application of all-weather MXene energy storage catalytic materials.

Dual Localized Surface Plasmon Resonance effect enhances Nb2AlC/Nb2C MXene thermally coupled photocatalytic reduction of CO2 hydrogenation activity.

Nb2AlC/Nb2C MXene (NAC/NC) heterojunction photocatalysts with Schottky junctions were obtained by selective etching of the Al layer, resulting in 146.25 µmol·g-1 electrons and 15.28 µmol·g-1 holes stored in the heterojunction. The average conversion of NAC/NC thermally coupled photocatalytic reduction of CO2 under the simulated solar irradiation reached 110.15 µmol⋅g-1⋅h-1, and the CO selectivity reached over 92%, which was 1.49 and 1.74 times higher than that of pure Nb2AlC and Nb2C MXene, respectively. After light excitation, the localized surface plasmon resonance (LSPR) effect of holes distributed on the surface of Nb2C MXene crystals in the heterojunction will form high-energy thermal holes to dissociate H2 to H+ and reduce CO2 to form H2O at the same time. The high-energy electrons formed by the LSPR effect of Nb2C MXene and the conduction band electrons generated by the photoexcitation of Nb2C MXene can be migrated to Nb2AlC under the action of the interfacial Schottky junction to supplement the electrons needed for the LSPR effect of Nb2AlC, which continuously forms high-energy hot electrons to convert the adsorbed CO2 into *CO2-, b-HCO3, and HCOO. Subsequently, HCOO releases ⋅OH in a cyclic reaction to continuously reduce to form CO. The dual LSPR effect of Nb2AlC and Nb2C MXene is used to enhance the hydrogenation activity of thermally coupled photocatalytic reduction of CO2, which provides a new research idea for the application of MXene in thermally coupled photoreduction of CO2.

Construction of Ag/NaBiO3 with dual active sites for photocatalytic NO deep oxidation and long-lasting organic pollutants degradation in the dark.

Ag/NaBiO3 with dual active sites and high capacitance was prepared by the photo-deposition method. Upon light illumination, the reduction of Ag+ to Ag, the introduction of oxygen vacancies, and the electron storage in Ag nanoparticles simultaneously happened. NO, and O2 adsorbed and activated at Ag site and oxygen vacancy site, respectively, to produce active ON* and •O2- radical species. The increased concentrations of the active oxygen species and the pre-oxidation of NO resulted in the enhanced NO removal with inhibited production of NO2. Moreover, the high capacitance of Ag and the continuous charge transfer from defective NaBiO3 to Ag offered the enhanced and long-lasting dark catalytic activity of the Ag/NaBiO3. The stored electrons in Ag were directly released in dark to decompose methyl orange and/or tetracycline. This work provides a novel idea of designing and preparing a multifunctional catalytic material for environmental cleaning.

Defects and internal electric fields synergistically optimized g-C3N4-x/BiOCl/WO2.92 heterojunction for photocatalytic NO deep oxidation.

In this work, g-C3N4-x/BiOCl/WO2.92 heterojunction with "N-O" vacancies was prepared using NaBiO3 and WCl6 as raw materials and non-metal plasma of WO2.92 grew in-situ on the surface of BiOCl, resulting in the enhanced photocatalytic NO deep oxidation. XPS tests and DFT calculation indicated the formation of internal electric fields from g-C3N4-x to BiOCl, BiOCl to WO2.92, which induced the transition from Ⅱ-Ⅱ-type to double Z-scheme hetero-structure. High separation efficiency, prolong lifetime and strong redox ability of photo-generated electron-hole pairs were simultaneously achieved due to the charge capture effect of defects and double Z-scheme mechanism. Therefore, g-C3N4-x/BiOCl/WO2.92 exhibited the significantly increased NO removal rates from 21.17% (BiOCl/WO2.92) and 36.52% (g-C3N4-x) to 68.70% and the main oxidation product of NO was NO3-. This study revealed that the carrier dynamics of heterojunction photocatalysts could be optimized by the synergistic effect of defects and internal electric fields to achieve photocatalytic NO deep oxidization.

Dual defects and build-in electric field mediated direct Z-scheme W18O49/g-C3N4-x heterojunction for photocatalytic NO removal and organic pollutant degradation.

In this work, dual defects mediated W18O49/g-C3N4-x heterojunction was prepared by in-situ hydrothermal method. The conversion from Ⅱ-type to Z-scheme heterojunction was achieved due to the formation of build-in electric field from g-C3N4-x to W18O49. Tests results indicated that the LSPR hot electrons of W18O49 could directly drive oxygen reduction reaction to generate O2- species and the partial electrons of g-C3N4-x were captured by O defect states of W18O49 to stabilize its free charge density, resulting in the continuous generation of high-energy hot electrons. The photo-generated carriers had the stronger redox ability compared with g-C3N4-x and W18O49 due to the Z-scheme charge transfer paths. Combined with the promoted exciton dissociation induced by N vacancies, the enhanced light absorption and accelerated carriers' separation induced by near-field enhancement effect in visible-NIR range of oxygen vacancies, W18O49/g-C3N4-x heterojunction exhibited enhanced photocatalytic performance for NO removal and full-solar-spectrum-driven pollutants degradation.