A Schottky/Z-Scheme Hybrid for Augmented Photocatalytic H2 and H2O2 Production.

The prodigious employment of fossil fuels to conquer the global energy demand is becoming a dreadful threat to the human society. This predicament is appealing for a potent photocatalyst that can generate alternate energy sources via solar to chemical energy conversion. With this interest, we have fabricated a ternary heterostructure of Ti3C2 nanosheet modified g-C3N4/Bi2O3 (MCNRBO) Z-scheme photocatalyst through self-assembly process. The morphological analysis clearly evidenced the close interfacial interaction between g-C3N4 nanorod, Bi2O3 and Ti3C2 nanosheets. The oxygen vacancy created on Bi2O3 surface, as suggested by XPS and EPR analysis, supported the Z-scheme heterojunction formation between g-C3N4 nanorod and Bi2O3 nanosheets. The collaborative effect of Z-scheme and Schottky junction significantly reduced charge transfer resistance promoting separation efficiency of excitons as indicated from PL and EIS analysis. The potential of MCNRBO towards photocatalytic application was investigated by H2O2 and H2 evolution reaction. A superior photocatalytic H2O2 and H2 production rate for MCNRBO is observed, which are respectively around 5 and 18 folds higher as compared to pristine CNR nanorod. The present work encourages for the development of a noble, eco-benign and immensely efficient dual heterojunction based photocatalyst, which can acts as saviour of human society from energy crisis.

Augmented photocatalysis induced by 1T-MoS2 bridged 2D/2D MgIn2S4@1T/2H-MoS2 Z-scheme heterojunction: mechanistic insights into H2O2 and H2 evolution.

In the realm of composite photocatalysts, the fusion of the co-catalyst effect with interfacial engineering is recognized as a potent strategy for facilitating the segregation and migration of photo-induced charge carriers. Herein, an innovative mediator-based Z-scheme hybrid, i.e. MIS@1T/2H-MoS2, has been well designed by pairing MIS with 1T/2H-MoS2via a facile hydrothermal strategy as a competent photocatalyst for H2O2 and H2 generation. The co-catalyst, i.e. metallic 1T-phase bridging between semiconducting 2H-MoS2 and MIS, serves as a solid state electron mediator in the heterostructure. Morphological findings revealed the growth of 1T/2H-MoS2 nanoflowers over MIS microflowers, verifying the close interaction between MIS and 1T/2H-MoS2. By virtue of accelerated e-/h+ pair separation and migration efficiency along with a proliferated density of active sites, the MMoS2-30 photocatalyst yields an optimum H2O2 of 35 µmol h-1 and H2 of 370 µmol h-1 (ACE of 5.9%), which is 3 and 2.7 fold higher than pristine MIS. This obvious enhancement can be attributed to photoluminescence and electrochemical aspects that substantiate the diminished charge transfer resistance along with improved charge carrier separation, representing a good example of a noble metal-free photocatalyst. The proposed Z-scheme charge transfer mechanism is aided by time-resolved photoluminescence (TRPL), XPS, radical trapping experiments, and EPR analysis. Overall, this endeavour provides advanced insights into the architecture of noble metal-free Z-scheme heterostructures, offering promising prospects in photocatalytic applications.

Nanoarchitecture of a Ti3C2@TiO2 Hybrid for Photocatalytic Antibiotic Degradation and Hydrogen Evolution: Stability, Kinetics, and Mechanistic Insights.

Designing of a visible-light-driven semiconductor-based heterojunction with suitable band alignment and well-defined interfacial contact is considered to be an effective strategy for the transformation of solar-to-chemical energy and environmental remediation. In this context, MXenes have received tremendous attention in the research community due to their merits of abundant derivatives, elemental composition, excellent metallic conductivity, and surface termination groups. Meanwhile, a facile synthetic strategy for MXene-derived TiO2 nanocomposites with stable framework and higher photocatalytic activity under visible-light irradiation still remains a challenge for researchers. Herein, we report a novel synthetic strategy of preparing a two-dimensional Ti3C2@TiO2 nanohybrid by a facile reflux method under acidic conditions. In this oxidation reaction, protonation of the hydroxyl terminal group of MXene creates Ti more electrophilic and susceptible to an oxidative nucleophilic addition reaction with the presence of both water and oxygen. The physicochemical properties of the nanohybrid Ti3C2@TiO2 were verified by varieties of characterization techniques. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy analysis specifically elucidated the intimate interfacial interaction between Ti3C2 and TiO2. The optimized Ti3C2@TiO2-48 h photocatalyst exhibited the highest tetracycline hydrochloride (TCH, 90% in 90 min) degradation efficiency in comparison to pristine TiO2 with a rate constant (k) of 0.02463 min-1. The major contribution of •O2- and •OH radicals throughout photocatalytic TCH degradation was confirmed by the trapping experiment. Moreover, the photocatalyst showed the highest hydrogen generation rate of 140.8 µmol h-1 along with an apparent conversion efficiency of 2.2%. The excellent photocatalytic activity of Ti3C2@TiO2 originated from the superior electrical conductivity of cocatalyst Ti3C2, which facilitated spatial photogenerated e-/h+ separation and transfer at the Ti3C2 MXene@TiO2 interface. Overall, this research work will describe a promising protocol of designing MXene-derived photocatalysts toward efficient environmental remediation and wastewater treatment applications.

Architecture and Kinetic Studies of Photocatalytic H2O2 Generation and H2 Evolution through Regulation of Spatial Charge Transfer via Z-Scheme Path over a (001) Facet Engineered TiO2@MXene/B-g-C3N4 Ternary Hybrid.

Spatial charge separation and migration are the critical shortcomings dominating the core energy conversion corridors of photocatalytic systems. Here, a biomimetic multi-interfacial architecture providing strong coupled interaction and rapid charge transmission for photostable and competent photocatalytic H2O2 production and H2 evolution is proposed. The triple-hybrid all-solid-state Z-scheme system was formed with the (001) facet exposed TiO2 nanosheets derived from MXene layers and B-g-C3N4 nanosheets (M/(001)TiO2@BCN) through an electrostatic self-assembly strategy with intimate electronic interaction due to Ti orbital modulation and proper stacking among the hybrids. The metallic and highly conductive MXene layers act as solid state electron mediators in the Z-scheme heterojunction that promote electron-hole separation and migration efficiency. Specifically, the MTBCN-12.5 composite provides optimum yield of H2O2 up to 1480.1 µmol h-1 g-1 and a H2 evolution rate of 408.4 µmol h-1 (with ACE 6.7%), which are 4 and 20 fold greater than the pristine BCN, respectively. The enhanced photocatalytic performance is systematically identified by the increased surface area, higher cathodic and anodic current densities of -1.01 and 2.27 mA cm-2, delayed charge recombination as supported by PL and EIS measurement, and excellent photostability. The Z-scheme charge transfer mechanism is validated by time-resolved photoluminescence (TRPL) analysis, cyclic voltametric analysis, and the radical trapping experiment as detected by PL analysis. This research marks a substantial advancement and establishes the foundation for future design ideas in accelerating charge transfer.

Robust direct Z-scheme exciton transfer dynamics by architecting 3D BiOI MF-supported non-stoichiometric Cu0.75In0.25S NC nanocomposite for co-catalyst-free photocatalytic hydrogen evolution.

Designing promising photocatalytic systems with wide photon absorption and better exciton separation ability is a cutting-edge technology for enhanced solar-light-driven hydrogen production. In this context, non-stoichiometric Cu0.75In0.25S nanocrystals (CIS NCs) coupled with three-dimensional (3D) BiOI micro-flowers (BOI MFs) were synthesized through an ultra-sonication strategy forming a CIS-BOI heterojunction, which was well supported by XRD, photocurrent, XPS and Mott-Schottky analyses. Further, the co-catalyst-free CIS-BOI binary hybrid shows improved hydrogen evolution, i.e., 588.72 µmol h-1, which is 3.2 times greater than the pristine CIS NC (183.97 µmol h-1). Additionally, the binary composite confers an apparent conversion efficiency (ACE) of 9.44% (8.90 × 1016 number of H2 molecule per sec), which is extensively attributed to the robust charge carrier separation and transfer efficiency via the direct Z-scheme mechanism (proved through superoxide and H2 evolution activity). Moreover, the broad photon absorption range and productive exciton separation over the CIS-BOI composite are substantially justified by UV-Vis DRS, PL, EIS and photocurrent measurements.

Exfoliated Boron Nitride (e-BN) Tailored Exfoliated Graphitic Carbon Nitride (e-CN): An Improved Visible Light Mediated Photocatalytic Approach towards TCH Degradation and H2 Evolution.

A series of 2D/2D exfoliated boron nitride/exfoliated g-C3N4 nanocomposites denoted as e-BN/e-CN have been successfully prepared using a simple in situ technique. The successful deposition of e-BN on e-CN was confirmed from high-resolution transmission electron microscopy analysis. According to electrochemical measurements, 1.5 wt % e-BN/e-CN nanocomposites showed 1.5 times more photocurrent than e-CN, which indicates the successful formation of an e-BN/e-CN heterostructure. The photocatalytic activities of the e-CN and e-BN/e-CN composites were investigated through photocatalytic tetracycline hydrochloride (TCH) degradation and H2 evolution under visible light illumination. The 1.5 wt % e-BN/e-CN composite demonstrated the highest photocatalytic activities, which are about 21 and 1.5 fold greater than e-CN towards H2 generation with an apparent conversion efficiency of 2.34% and TCH degradation, respectively. The improved photocatalytic activities of e-BN/e-CN photocatalysts were ascribed to the augmented light-harvesting ability and enhanced separation efficiency of charge carriers. Lower photoluminescence intensity and a smaller arc value in the impedance spectra again proved the reduced recombination of the e--h+ pairs in the e-BN/e-CN nanocomposites. Trapping experiments show that •O2-, h+, and •OH radicals are the predominant reactive species that accelerated the photocatalytic activities of e-BN/e-CN composites. This study opens up a new window towards the fabrication of such 2D/2D nanocomposites in the field of photocatalysis.

Resurrection of boron nitride in p-n type-II boron nitride/B-doped-g-C3N4 nanocomposite during solid-state Z-scheme charge transfer path for the degradation of tetracycline hydrochloride.

Antibiotic contaminants have received much attention due to the increasing serious environmental concerns. In this work, for the first time, we have fabricated a series of significant type-II p-n heterostructure with Z-scheme charge transfer between p-type B-doped g-C3N4 with different proportion of n-type BN through a simple in-situ growth process. PXRD, FTIR, UV-Vis, FESEM, HRTEM and EIS analysis were applied for the detailed characterization of the as-prepared composites to study the crystal phase, structural features, optical and electrical properties. The photocatalytic behaviour of BN/BCN photocatalyst was investigated by the degradation of tetracycline hydrochloride under solar light illumination. Experimental results revealed that about 88.1% of TCH was degraded by the BN/BCN composite containing 4 wt% BN in the BN/BCN matrix, in 60 min of solar light irradiation. Reduction in recombination rate of photo generated electron-hole pair's and enhanced visible light absorption ability is credited to the enhanced photocatalytic performance of BN/BCN composite. Trapping experiment for the scavenging agents has confirmed that superoxide (O2¯) and hydroxyl (OH) radicals are the main reactive species during the TCH degradation process. The high stability shown by the BN/BCN composite opens a new path for designing of significant BN based Z-scheme photocatalyst for prevention of environmental issues.