Increasing electron density by surface plasmon resonance for enhanced photocatalytic CO2 reduction

Construction of CdIn2S4/MXene-TiO2 Z-Scheme Heterojunction for High-Gain Organic Photoelectrochemical Transistor to Achieve Maximized Transconductance at Zero Bias

Interfacial charge-carrier complexation is a bottleneck problem governing the gating effect of organic photoelectrochemical transistor (OPECT) biosensors. Therefore, it has long been desired to enhance the OPECT gating effect and realize the maximum transconductance at zero bias. In this study, an in situ engineered heterojunction gating and nano-enzymatic catalytic integration of OPECT-colorimetric dual-mode sensing platform is developed for dibutyl phthalate detection. Specifically, highly efficient photoactive CdIn2S4/MXene-TiO2 Z-scheme heterojunction is constructed by two-step in situ engineering to promote effective separation of electron-hole pairs to achieve sensitive gating of poly(ethylene dioxythiophene):poly(styrene sulfonate)-based OPECT. Target-induced rolling circle amplification is used as the signal amplification unit, and Ag@Carbon Sphere (Ag─CS) is used as the signal conditioning element, which on the one hand causes shunting of photogenerated electrons, leading to energy transfer and reduced gating. At the same time, Ag─CS acts as a peroxidase-mimicking nanozyme to oxidize the TMB discoloration. Importantly, the prepared sensor exhibits good selectivity and high sensitivity for the detection of dibutyl phthalate with a detection limit of 0.08 fM and also shows superior detection ability in real water bodies. Therefore, the sensor provides an ideal choice for toxic molecule detection and has a promising application in environmental monitoring and food analysis.

Z-scheme CeO2-TiO2@CNT Heterojunction for Efficient Photoredox Removal of Mix Pollutants (CPF, MB, MO, and RhB)

Z-scheme CeO2-TiO2@CNT (CTC) heterojunction is fabricated using hydrothermal method and evaluated for removing mixed pollutants (MIX-P) from ciprofloxacin (CPF) and textile contaminations. CTC demonstrated ≈99% removal efficiency against MIX-P under solar irradiation of ≈105 lumens. High removal efficiency of CTC is attributed to reduced bandgap (Eg), 2.65 eV, and high specific surface area (68.193 m2 g-1). Lower Eg extends light absorption that generates more charge carriers and reactive species, RS (•O2 -, h+, •OH), to facilitate the photocatalytic removal process. These RS are confirmed through trapping experiments using IPA, N2, and KI. Binding energies of 282.5, 283.7, and 285 eV, corresponding to Ti─C, Ti─O─C, and Ce─C bondings, indicated coupling of TiO2, CeO2, and CNT within the CTC structure. Ionic and pH tests confirmed lower photocatalytic efficiency of CTC in an alkaline environment. Photocurrent density and EIS measurements provide insights into the charge carrier dynamics, while HPLC-MS analysis offered information on degradation pathway and identification of intermediates in the removal process. DFT studies confirmed the adjustments in electronic states, structural modifications, and band alignments in agreement with experimental results. This study highlights the potential of CTC as highly effective catalyst for sustainable removal of mixed pollutants from wastewater.

Oxygen atom activated ZIF-67/carbon cloth in plasma system for CO2 reduction

ZIF-67 was grown in situ on carbon cloth (CC) using a simple one-step method. The prepared ZIF-67/CC electrodes exhibited excellent CO2 reduction reaction (CO2RR) performance in a dielectric barrier discharge plasma reactor. The highest concentrations of produced formic acid and formaldehyde were 9.16 and 0.068 mmol L-1 at a reaction time of 1 h, respectively. The high performance is related to the unique high aspect ratio structure and pad-like cavity of ZIF-67, which results not only in an increase in the specific surface area for CO2 adsorption but also in the hydrophobicity of the electrode. Unexpectedly, the superoxide radical (·O2-) greatly affects the reduction performance of the electrode. In addition, the ZIF-67/CC electrode maintained good CO2RR performance in the presence of different pollutants, and the production of formic acid and formaldehyde increased to 10.81 and 0.11 mmol L-1 at 1 h with the addition of 10 mg L-1 phenol. This research provides new directions in the field of plasma catalysis.

Rich Sulfur Vacancies and Reduced Schottky Barrier Height Synergistically Enable Au/ZnIn2S4 with Enhanced Photocatalytic CO2 Reduction into CO

Constructing the plasmonic metal/semiconductor heterostructure with a suitable Schottky barrier height (SBH) and the sufficiently reliable active sites is of importance to achieve highly efficient and selective photocatalytic CO2 reduction into hydrocarbon fuels. Herein, we report Au/sulfur vacancy-rich ZnIn2S4 (Au/VSR-ZIS) hierarchical photocatalysts, fabricated via in situ photodepositing Au nanoparticles (NPs) onto the nanosheet self-assembled ZnIn2S4 (ZIS) micrometer flowers (MFs) with rich sulfur vacancies (VS). Density functional theory (DFT) calculations confirm that for the Au/VSR-ZIS system, the Au NPs serve as the reaction sites for H2O oxidation, and the VSR-ZIS MFs serve as those for CO2 reduction. The rich VS in the Au/VSR-ZIS hybrid can reduce its SBH so as to boost more hot electrons in the Au NPs across its Schottky barrier and then inject into the conduction band (CB) of the VSR-ZIS MFs. In addition, VS can also act as the electron sink to trap the photogenerated electrons, retarding the recombination of photogenerated carriers. The two merits effectively enhance the photogenerated electron density in the surface of VSR-ZIS MFs, availing CO2 photoreduction. In addition, the introduction of rich VS in the Au/VSR-ZIS hybrid can offer more active sites, benefiting the CO2 adsorption and accelerating the desorption of CO* from the surface of the photocatalyst. Therefore, under visible light illumination with no sacrificial reagent, the optimum photocatalyst (Au/VSR-ZIS-0.4) presents the enhanced and selective CO2 photoreduction into CO (8.15 μmol g-1h-1 and near 100%), which are superior to those of most of ZIS-based and plasmon-based photocatalysts. The photocatalytic activity is about 40.0-fold as high as that of the Vs-poor-ZIS (VSP-ZIS) MFs. This work contributes a viable strategy for designing highly efficient plasmonic photocatalysts by using the synergism of the anion vacancies and the optimized SBH induced by them.

Construction of an In2O3/Bi2S3 Z-Scheme Heterojunction for Enhanced Photocatalytic CO2 Reduction

Photocatalytic conversion of CO2 to hydrocarbon fuel is a potential strategy to solve energy shortage and mitigate the greenhouse effect. Here, direct Z-scheme heterojunction photocatalysts (In2O3/Bi2S3) without an electron mediator are prepared by a simple hydrolysis method. The In2O3/Bi2S3 composite photocatalysts show greatly boosted photoactivity on CO2 conversion to CO compared with the pristine In2O3 and Bi2S3. The highest CO evolution rate of 2.67 μmol·g-1·h-1 is achieved by In2O3/Bi2S3-3, without any sacrificial agent or cocatalyst, which is about 3.87 times that of In2O3 (0.69 μmol·g-1·h-1). The boosted photocatalytic performance of In2O3/Bi2S3 composite catalysts can be ascribed to the establishment of a Z-scheme heterojunction, improving the photoabsorption and facilitating charge separation and transfer. This study provides a reference for designing and fabricating high-efficiency Z-scheme heterojunction photocatalysts for photocatalytic CO2 reduction.

Improved Charge Separation and CO2 Affinity of In2O3 by K Doping with Accompanying Oxygen Vacancies for Boosted CO2 Photoreduction

The CO2 photocatalytic conversion efficiency of the semiconductor photocatalyst is always inhibited by the sluggish charge transfer and undesirable CO2 affinity. In this work, we prepare a series of K-doped In2O3 catalysts with concomitant oxygen vacancies (OV) via a hydrothermal method, followed by a low-temperature sintering treatment. Owing to the synergistic effect of K doping and OV, the charge separation and CO2 affinity of In2O3 are synchronously promoted. Particularly, when P/P0 = 0.010, at room temperature, the CO2 adsorption capacity of the optimal K-doped In2O3 (KIO-3) is 2336 cm3·g-1, reaching about 6000 times higher than that of In2O3 (0.39 cm3·g-1). As a result, in the absence of a cocatalyst or sacrificial agent, KIO-3 exhibits a CO evolution rate of 3.97 μmol·g-1·h-1 in a gas-solid reaction system, which is 7.6 times that of pristine In2O3 (0.52 μmol·g-1·h-1). This study provides a novel approach to the design and development of efficient photocatalysts for CO2 conversion by element doping.

Construction of BiOIO3/AgIO3 Z-Scheme Photocatalysts for the Efficient Removal of Persistent Organic Pollutants under Natural Sunlight Illumination

The efficient removal of persistent organic pollutants (POPs) in natural waters is vital for human survival and sustainable development. Photocatalytic degradation is a feasible and cost-effective strategy to completely disintegrate POPs at room temperature. Herein, we develop a series of direct Z-scheme BiOIO₃/AgIO₃ hybrid photocatalysts via a facile deposition-precipitation method. Under natural sunlight irradiation, the light intensity of which is ∼40 mW/cm², a considerable rate constant of 0.185 min^-1 for photodecomposing 40 mg/L MO is obtained over 0.5 g/L Bi@Ag-5 composite photocatalyst powder, about 92.5 and 5.3 times higher than those of pristine AgIO₃ and BiOIO₃. The photoactivity of Bi@Ag-5 for photodecomposing MO under natural sunlight illumination surpasses most of the reported photocatalysts under Xe lamp illumination. After natural sunlight irradiation for 20 min, 95% of MO, 82% of phenol, 78% of 2,4-DCP, 54% of ofloxacin, and 88% of tetracycline hydrochloride can be photodecomposed over Bi@Ag-5. Relative to the commercial photocatalyst TiO₂ (P25), Bi@Ag-5 exhibits greatly higher photoactivity for the treatment of MO-phenol-tetracycline hydrochloride mixture pollutants in the scale-up experiment of 500 mL of solution, decreasing COD, TOC, and chromaticity value by 52, 19, and 76%, respectively, after natural sunlight irradiation for 40 min. The photodegradation process and mechanism of MO have been systematically investigated and proposed. This work provides an archetype for designing efficient photocatalysts to remove POPs.