MXene-based Photocatalysts Research Articles

Recent advancements in MXene-based nanocomposites as photocatalysts for hazardous pollutant degradation - A review

The recent expeditious industrialization and urbanization showcase the increasing need for renewable and non-renewable energy and the severe environmental crisis. In this regard, numerous 2-dimensional (2D) nanomaterials have been developed as a facile approach to meet the futuristic energy essentials and to resolve the crisis. In contrast, the newly explored 2D MXenes (transition metal carbide/nitrides/carbonitride) have been employed as an intriguing material for various environmental applications. This development is accredited to their unique properties, which include a vast surface area, strong electrical conductivity, fascinating photophysical properties, high mechanical properties, stability in an aqueous medium, high hydrophilicity, biocompatibility, ease of functionalization, and excellent thermal properties. MXenes act as a potential candidate in water desalination, energy storage devices such as electrodes of Li-ion batteries and pseudo capacitors, hydrogen production, sensors, and wastewater treatment. This review article deliberates the synthesis of MXene and nanocomposites of MXene and their photo-catalytic actions against various toxic pollutants such as organic dyes and heavy metals in wastewater. This review also precises the various preparation methods of MXene-based photocatalyst and the enhanced photocatalytic activity of MXene and MXene-based nanocomposites in wastewater treatment. Also, it details the attempts made to improve the photocatalytic activity of MXene-based nanocomposites in terms of their structural compositions. In addition, the merits and demerits of the MXene-based photocatalysts are deliberated, which may pave the way for future research in this arena.

Composite nanoarchitectonics with TiO2 nanocrystals and superior thin Ti3C2Tx nanosheets towards efficient NO removal

Accordion-like Ti3C2Tx MXene supplied a possibility to construct two-dimensional composites with novel performance. In this paper, few-layered Ti3C2Tx MXene was created via a chemical etching strategy. The oxidation in-situ using a powerful alkaline solution resulted successfully in TiO2 nanocrystals grown on Ti3C2Tx nanosheets. The alkaline treatment adjusted terminations of the Ti3C2Tx MXene and controlled the oxidation degree by changing temperature. The ratio of Ti3C2Tx and TiO2 was finally optimized. Because of Ti3C2Tx nanosheets with well conductivity and excellent light absorption as well as TiO2 nanocrystal arrays on Ti3C2Tx nanosheets with a high specific surface area and more active sites, TiO2/Ti3C2Tx composites revealed excellent photocatalystic activity, especially for NO removal. The improvement of separation and transfer efficiency of phootogenerated carriers is ascribed to the microstructure of TiO2/Ti3C2Tx composites. The composite sample synthesized at 75 °C revealed the best NO removal efficiency, in which 70% of NO was removed at a concentration of 600 ppb. This study offers a new thought for preparing high performance MXene-based photocatalysts.

Enhanced Photocatalytic Hydrogen Production of ZnIn2S4 by Using Surface-Engineered Ti3C2Tx MXene as a Cocatalyst.

Developing efficient and stable photocatalysts is crucial for photocatalytic hydrogen production. Cocatalyst loading is one of the effective strategies for improving photocatalytic efficiency. Here, Ti3C2Tx (Tx = F, OH, O) nanosheets have been adopted as promising cocatalysts for photocatalytic hydrogen production due to their metallic conductivity and unique 2D characterization. In particular, surface functionalized Ti3C2(OH)x and Ti3C2Ox cocatalysts were synthesized through the alkalization treatment with NaOH and a mild oxidation treatment of Ti3C2Fx, respectively. ZnIn2S4/Ti3C2Tx composites, which were fabricated by the in-situ growth of ZnIn2S4 nanosheets on the Ti3C2Tx surface, exhibited the promoted photocatalytic performance, compared with the parent ZnIn2S4. The enhanced photocatalytic performance can be further optimized through the surface functionalization of Ti3C2Fx. As a result, the optimized ZnIn2S4/Ti3C2Ox composite with oxygen functionalized Ti3C2Ox cocatalyst demonstrated excellent photocatalytic hydrogen evolution activity. The characterizations and density functional theory calculation suggested that O-terminated Ti3C2Ox could effectively facilitate the transfer and separation of photogenerated electrons and holes due to the formation of a Schottky junction, with the largest difference in work function between ZnIn2S4 and Ti3C2Ox. This work paves the way for photocatalytic applications of MXene-based photocatalysts by tuning their surface termination groups.

Surface -O terminated urchin-like TiO2/Ti3C2Ox (MXene) as high performance photocatalyst: Interfacial engineering and mechanism insight

The surface groups of MXene act as a decisive role on the performance of MXene-based photocatalysts. In this work, TiO2 nano-whiskers were grown in-situ on Ti3C2Tx, through a hydrothermal and post-heat treatment process, meanwhile, the surface groups of Ti3C2Tx were unified -O adsorption. The as-prepared urchin-like TiO2/Ti3C2Ox composite have efficient activity for photocatalytic hydrogen evolution and degradation of levofloxacin (LEV). The optimized hydrogen evolution reaction (HER) performance reached 346.8 μmol g-1 h−1, and the apparent quantum yield at 313 nm was 7.67%. Its hydrogen production performance and degradation rate of LEV were 9.7 and 7.7 folds higher than those of pure TiO2, respectively. The -O terminated Ti3C2Ox achieving a work function about 0.3 eV larger than TiO2, as both DFT calculation and UPS measurement depicted. Therefore, the photogenerated e-/h+ were separated at the TiO2/Ti3C2Ox interface via Schottky junction, a large amount of e- was enriched on Ti3C2Ox, which enabled the photocatalyst with remarkable charge separation and photocatalytic performance. Meanwhile, the reaction pathways of TiO2/Ti3C2Ox photocatalytic HER and LEV degradation/mineralization were carefully investigated. This study underlines the significance of surface groups on photocatalysts composed of MXenes, and sheds light on the new approach to the rational design of high-efficiency MXene-based photocatalysts.

Interface plasmon damping in the Cd33Se33/Ti2C MXene heterostructure.

MXenes, a class of two-dimensional materials, have shown immense potential in various applications such as energy storage, electromagnetic shielding, solar cells, smart fabrics, optoelectronics, and plasmonics. In this study, we employ first-principles density functional theory (DFT) and time-dependent DFT calculations to investigate a semiconductor-metal heterostructure composed of a Cd33Se33 cluster and Ti2C MXene monolayer flakes. Our research focuses on the formation and damping of localized surface plasmon resonances (LSPRs) within this heterostructure. We discover that the Cd33Se33/Ti2C interface gives rise to a Schottky barrier. Importantly, this interface formation results in the damping of the Ti2C LSPR, thereby facilitating the transfer of electrons into the Cd33Se33 cluster. By directly visualizing the LSPR damping phenomenon, our study enhances our understanding of the semiconductor-MXene interface and provides novel insights for the design of MXene-based photocatalysts.

Design and synthesis of TiO2/Ti3C2 composites for highly efficient photocatalytic removal of acetaminophen: The relationships between synthesis parameters, physicochemical properties, and photocatalytic activity

In this study, we report the potential of TiO2/Ti3C2 composite fabricated by oxidation of MXene for degradation of persistent organic pollutants. The effect of the synthesis conditions (time, temperature, and reaction environment) on the morphology, physicochemical properties, and photocatalytic activity was investigated. It was found that acetaminophen degradation was positively correlated with TiO2 content in the composite structure. Furthermore, the findings confirmed that the synthesis reaction environment strongly influenced the obtained materials photocatalytic activity. The TiO2/Ti3C2 composite obtained by solvothermal route in the presence of hydrochloric acid and ammonium fluoride exhibited the highest efficiency towards acetaminophen degradation than other composite materials, for which ACT removal reached 92 % within 60 min of irradiation under simulated solar light. The improved photocatalytic performance can be attributed to the presence of anatase-rutile polymorphs exposing highly active { 0 0 1} and { 1 0 1} facets coupled with MXene. Superoxide anion radicals and hydroxyl radicals played a major role in ACT degradation. Moreover, 3-hydroxyacetaminophen was detected as the first intermediate of ACT degradation, leading quickly to aromatic ring opening and production of aliphatic acids. Overall, this work provides an effective strategy for designing novel and efficient MXene-based photocatalysts for the degradation of emerging contaminants in water systems.

MXene-Based Photocatalysts in Degradation of Organic and Pharmaceutical Pollutants.

These days, explorations have focused on designing two-dimensional (2D) nanomaterials with useful (photo)catalytic and environmental applications. Among them, MXene-based composites have garnered great attention owing to their unique optical, mechanical, thermal, chemical, and electronic properties. Various MXene-based photocatalysts have been inventively constructed for a variety of photocatalytic applications ranging from pollutant degradation to hydrogen evolution. They can be applied as co-catalysts in combination with assorted common photocatalysts such as metal sulfide, metal oxides, metal–organic frameworks, graphene, and graphitic carbon nitride to enhance the function of photocatalytic removal of organic/pharmaceutical pollutants, nitrogen fixation, photocatalytic hydrogen evolution, and carbon dioxide conversion, among others. High electrical conductivity, robust photothermal effects, large surface area, hydrophilicity, and abundant surface functional groups of MXenes render them as attractive candidates for photocatalytic removal of pollutants as well as improvement of photocatalytic performance of semiconductor catalysts. Herein, the most recent developments in photocatalytic degradation of organic and pharmaceutical pollutants using MXene-based composites are deliberated, with a focus on important challenges and future perspectives; techniques for fabrication of these photocatalysts are also covered.

A Review on MXene Synthesis, Stability, and Photocatalytic Applications.

Photocatalytic water splitting, CO2 reduction, and pollutant degradation have emerged as promising strategies to remedy the existing environmental and energy crises. However, grafting of expensive and less abundant noble-metal cocatalysts on photocatalyst materials is a mandatory practice to achieve enhanced photocatalytic performance owing to the ability of the cocatalysts to extract electrons efficiently from the photocatalyst and enable rapid/enhanced catalytic reaction. Hence, developing highly efficient, inexpensive, and noble-metal-free cocatalysts composed of earth-abundant elements is considered as a noteworthy step toward considering photocatalysis as a more economical strategy. Recently, MXenes (two-dimensional (2D) transition-metal carbides, nitrides, and carbonitrides) have shown huge potential as alternatives for noble-metal cocatalysts. MXenes have several excellent properties, including atomically thin 2D morphology, metallic electrical conductivity, hydrophilic surface, and high specific surface area. In addition, they exhibit Gibbs free energy of intermediate H atom adsorption as close to zero and less than that of a commercial Pt-based cocatalyst, a Fermi level position above the H2 generation potential, and an excellent ability to capture and activate CO2 molecules. Therefore, there is a growing interest in MXene-based photocatalyst materials for various photocatalytic events. In this review, we focus on the recent advances in the synthesis of MXenes with 2D and 0D morphologies, the stability of MXenes, and MXene-based photocatalysts for H2 evolution, CO2 reduction, and pollutant degradation. The existing challenges and the possible future directions to enhance the photocatalytic performance of MXene-based photocatalysts are also discussed.

Steering interfacial charge kinetics: Synergizing cocatalyst roles of Ti3C2Mx (MXene) and NCDs for superior photocatalytic performance over TiO2

Steering the kinetics of photoexcited electron-hole pairs to achieve the elongated lifetime of carrier is one of key strategies to enhance the photocatalytic performance. Here, 0D/2D/2D NCDs/TiO2/Ti3C2Mx photocatalyst is fabricated for the first time via hydrothermal route, the mixed group terminated MXene (Ti3C2Mx, M = -O, –OH, -F) and N-doped carbon dots (NCDs) are exploited as an electron acceptor and hole mediator, respectively, enhancing the photocatalytic activity of TiO2 nanosheets by steering interfacial charge kinetics. The photocatalytic hydrogen evolution and tetracycline hydrochloride (TC) degradation of 0.1 NCDs/TiO2/Ti3C2Mx-12 h are ∼ 4 and 9 times higher than those of TiO2, respectively. UPS and DFT calculation results determine that the work function (Φ) of Ti3C2Mx as 4.16 eV and 3.63 eV, respectively, which are larger than that of bare Ti3C2 (Φ = 3.55 eV), while the work function of TiO2 and NCDs are 3.98 and 3.09 eV, respectively. The results of charge transfer dynamics reveal that the photocatalytic enhancement of NCDs/TiO2/Ti3C2Mx is dominantly attributed to the synergizing cocatalyst roles of Ti3C2Mx (MXene) and NCDs. The insight into the surface termination dominated electronic property of MXene and synergistic steering the interfacial charge kinetics is an effective way to fabricate high performance MXene-based photocatalysts.

Boosted CO2 photoreduction performance on Ru-Ti3CN MXene-TiO2 photocatalyst synthesized by non-HF Lewis acidic etching method

Photocatalytic CO2 reduction to produce value-added products is considered a promising solution to solve the global energy crisis and the greenhouse effect. In this study, Ti3CN MXene was synthesized using a Lewis acidic etching method without the usage of toxic hydrofluoric acid (HF). Ti3CN MXene was then used as a support for the in situ hydrothermal growth of TiO2 and Ru nanoparticles. In the presence of 0.5 wt% Ru, Ru-Ti3CN-TiO2 shows CO and CH4 production rates of 99.58 and 8.97 μmol/g, respectively, in 5 h under Xenon lamp irradiation, more than 20.5 and 9.3 times that of commercial P25. The enhancement in photocatalytic activity was attributed to the synergy between the in-situ growth of TiO2 on Ti3CN MXene and Ru nanoparticles. It was proven experimentally that Ti3CN MXene can provide abundant pathways for electron transfer. The separation and transfer of the photo-induced charge were further increased with the help of Ru and Ti3CN MXene, leaving more electrons to participate in the subsequent CO2 reduction reaction. We believe that this work will encourage more attention to designing environment-friendly MXene-based photocatalysts for CO2 photoreduction using the non-HF method.

Hierarchical ZnO/MXene (Nb2C and V2C) heterostructure with efficient electron transfer for enhanced photocatalytic activity

Recently, MXene has attracted much attention as photocatalysts for efficient pollutant degradation in the field of environmental remediation but a rapid recombination of photogenerated carriers usually leads to a decrease in the photocatalytic performance. Constructing a heterostructure is considered as an effective way to improve the catalytic performance of MXene-based photocatalysts due to the promoted interfacial electron transfer. In this work, the chimeric ZnO nanosheets with good carrier mobility were formed on the accordion-shaped MXene (Nb2C and V2C) surface to construct hierarchical ZnO/MXene heterostructure as a photocatalyst for dye degradation. The obtained ZnO/Nb2C and ZnO/V2C hierarchical structure exhibited excellent photocatalytic performance in the degradation of methylene blue (MB): the degradation rate reached 62.62% and 99.53%, respectively, after irradiation with ultraviolet light for 120 min. Also, the apparent degradation rate constants (k) were 0.00777 min−1 and 0.04317 min−1, respectively, which were 2.92 and 16.23 times higher than those of pure ZnO. This was probably attributed to the heterostructures between ZnO and MXene which could shorten the carrier transfer path, which could facilitate the transfer of photo-generated electrons from conduction band (CB) of ZnO to CB of MXene, thereby significantly improving the photocatalytic degradation efficiency. In addition, the ZnO/Nb2C and ZnO/V2C hierarchical structure showed good photocatalytic stability: the degradation rate remained at 58.6% and 97.3%, respectively, after 4 cycles while it only maintained at 22.0% for pure ZnO because the obtained ZnO/MXene hierarchical structure could provide uniform active sites on the surface and porous structure, preventing the aggregation of ZnO or MXene. Therefore, this work could provide a feasible design strategy to improve the catalytic performance of 2D photocatalysts and shed a light on the design of other photocatalysts.

Construction of BiOBr/Ti3C2/exfoliated montmorillonite Schottky junction: New insights into exfoliated montmorillonite for inducing MXene oxygen functionalization and enhancing photocatalytic activity

Currently, poor stability and excessive –F terminal groups of Ti3C2 MXene notably restrains the synthesis and potentiality exploitation of MXene-based photocatalysts. Herein we offered facile and cost-effective tactics by introducing exfoliated montmorillonite (MMTex) to efficiently inhibit oxidation of Ti3C2 during the hydrothermal synthesis process, simultaneously weakening the adverse effects of surface –F terminations and achieving surface oxygen (O) functionalization of Ti3C2. Ternary BiOBr/Ti3C2/MMTex was first fabricated via microsphere BiOBr assembled on O-functionalized MMTex/Ti3C2 using in-situ coprecipitation coupling with microwave hydrothermal method. Representative characterizations demonstrated that BiOBr/Ti3C2/MMTex possessed a stable hybrid structure, intimate interfacial coupling and superior photoelectric performance. Enhanced generation of •OH and •O2– radicals over the BiOBr/Ti3C2/MMTex photocatalysis system were confirmed in comparison to that of pristine BiOBr and BiOBr/Ti3C2, which owed to excellent separation and migration of photogenerated charges achieved by synergetic effects of Schottky barrier and Charges repulsion. Thus, BiOBr/Ti3C2/MMTex achieved superior degradation for multiple organic pollutants. Furthermore, the enhanced photocatalytic mechanisms, three plausible CIP degradation pathways, and detailed assessments of the biological toxicity of intermediates were proposed. The study provides a novelty option to exploit efficient and stable MXene-based photocatalysts by utilizing low-priced montmorillonite for environmental remediation.

MXenes based nano-heterojunctions and composites for advanced photocatalytic environmental detoxification and energy conversion: A review

Extensive research is being done to develop multifunctional advanced new materials for high performance photocatalytic applications in the field of energy production and environmental detoxification, MXenes have emerged as promising materials for enhancing photocatalytic performance owing to their excellent mechanical properties, appropriate Fermi levels, and adjustability of chemical composition. Numerous experimental and theoretical research works implied that the dimensions of MXenes have a significant impact on their performance. For photocatalysis to thrive in the future, we must understand the current state of the art for MXene in different dimensions. Using MXene co-catalysts in widely used in photocatalytic applications such as CO2 reduction, hydrogen production and organic pollutant oxidation, this study focuses on the most recent developments in MXenes based materials, structural modifications, innovations in reaction and material engineering. It has been reported that using 5 mg of CdS–MoS2-MXene researchers were able to generate as high as 9679 μmol/g/h hydrogen under visible light. The MXenes based heterojunction photocatalyst Co3O4/MXene was utilized to degrade 95% bisphenol A micro-pollutant in just 7 min. Numerous novel materials, their preparations and performances have been discussed. Depending upon the nature of MXene-based materials, the synthesis techniques and photocatalytic mechanism of MXenes as co-catalyst are also summarized. Finally, some final thoughts and prospects for developing highly efficient MXene-based photocatalysts are provided which will indeed motivate researchers to design novel hybrid materials based on MXenes for sustainable solutions to energy and pollution issues.

Photocatalysis over MXene-based hybrids: Synthesis, surface chemistry, and interfacial charge kinetics

Two-dimensional (2D) transition metal carbides and/or nitrides (MXenes) are a family of graphene-like 2D materials, with unique layered structures, high mechanical strength, excellent carrier mobility, and outstanding physical and chemical properties. In particular, the work function (Φ) of MXenes and Gibbs free energy of the adsorbed intermediate, such as H* (|△GH*|), can be regulated by their surface adsorption groups (–OH, –O, and –F), enabling the applications in the field of photocatalysis. This article systematically summarizes the recent advances of synthetic routes of MXene-based photocatalysts and discusses the interfacial charge kinetics and photogenerated charge transfer mechanism of MXene-based photocatalysts. Furthermore, major challenges and further research trends of MXene-based photocatalysts are also presented.

Activating two-dimensional Ti3C2Tx-MXene with single-atom cobalt for efficient CO2 photoreduction

Summary Artificial CO2 photoreduction to solar fuels represents an eco-friendly and sustainable solution to obtain “sunshine” feedstocks by using renewable energy media. Herein, we report that single cobalt atoms anchored on two-dimensional Ti3C2Tx-MXene nanosheets act as an efficient photocatalytic ensemble for visible-light CO2 reduction, wherein the Ti3C2Tx nanosheets bridge visible-light absorbers (ruthenium complex) with cobalt active sites. The single cobalt atoms build strong interactions with Ti3C2Tx by forming metal-oxygen/carbon bonds, resulting in the formation of the Co-Ti3C2Tx ensemble. As a result, the production rate of CO reaches a high value of 6.06 mmol h−1 g−1 over the optimal Co-Ti3C2Tx, which markedly exceeds previous MXene-based catalysts for CO2 photoreduction. Theoretical calculation manifests that the isolated Co atoms coordinated with Ti3C2Tx can effectively facilitate the generation of CO. This work may provide a new line of thought into the rational design of high-activity MXene-based photocatalysts toward artificial CO2 conversion.

State-of-the-art recent progress in MXene-based photocatalysts: a comprehensive review.

Recently, the emerging two-dimensional material MXene enjoys a high reputation due to its fascinating characteristics and shines in various research fields. Among them, MXene has received increasing attention and favor from the photocatalysis community due to its regular planar structure, outstanding metal conductivity, surface adjustable chemical properties, abundant derivatives, and excellent optical and thermal properties. There is no doubt that the introduction of MXene has endowed the photocatalytic system with extraordinary performance and has made an important impact in the field of advanced catalysis and chemical technology. Herein, on the one hand, we summarize the synthetic route of MXenes and MXene-derived 0D quantum dots (MQDs), and propose the corresponding improved synthetic strategies for the defects of MXenes obtained by the current synthetic methods. On the other hand, recent progress in MXene-based photocatalysts has been reviewed to provide a comprehensive dissection of their designs and applications. It is highly anticipated that these will present researchers with a one-stop point for the state-of-the-art development of MXene-based photocatalysts. Finally, the future opportunities and challenges of MXenes in the flourishing field of photocatalysis are also discussed.

Mechanism of surface and interface engineering under diverse dimensional combinations: the construction of efficient nanostructured MXene-based photocatalysts

Proposed scheme of the surface and interface engineering to improve the charge separation efficiency of MXene-based photocatalysts.

Review of MXene-based nanocomposites for photocatalysis

Since multilayered MXenes (Ti3C2Tx, a new family of two-dimensional materials) were initially introduced by researchers at Drexel University in 2011, various MXene-based nanocomposites have received increased attention as photocatalysts owing to their exceptional properties (e.g., rich surface chemistry, adjustable bandgap structures, high electrical conductivity, hydrophilicity, thermal stability, and large specific surface area). Therefore, we present a comprehensive review of recent studies on fabrication methods for MXene-based photocatalysts and photocatalytic performance for contaminant degradation, CO2 reduction, H2 evolution, and N2 fixation with various MXene-based nanocomposites. In addition, this review briefly discusses the stability of MXene-based nanophotocatalysts, current limitations, and future research needs, along with the various corresponding challenges, in an effort to reveal the unique properties of MXene-based nanocomposites.

Ti3C2 MXene-bridged Ag/Ag3PO4 hybrids toward enhanced visible-light-driven photocatalytic activity

As a novel transition metal carbides and/or carbonitrides, MXene possess two-dimensional characteristic, abundant surface hydrophilic functional groups, and excellent electrical conductivity that bestow a possibility to building MXene-based photocatalysts. Inspired by this, an emerging Ti3C2 MXene cocatalyst bridged Ag/Ag3PO4 to induce a highly visible-light-driven photocatalytic activity, synthesized by electrostatic self-assembly method and the partial reduction of Ag+ ions to Ag0 in MXene solution is reported. The resultant hybrids reveal a well-defined hybrid structures with Ag/Ag3PO4 anchoring on the layer structured Ti3C2 nanosheets. Benefiting from the unique structural features, the Ag/Ag3PO4/Ti3C2 hybrids present Ti3C2 content-dependent photocatalytic activity toward the methyl orange (MO) degradation and Cr(VI) reduction under visible-light irradiation. Remarkably, the Ag/Ag3PO4/Ti3C2 hybrid with 3 wt% Ti3C2 content achieves the greatest MO degradation efficiency and Cr(VI) reduction efficiency after irradiation for 1 h, which are increased to 1.72 and 1.46 times higher than that obtained on pristine Ag3PO4 nanoparticles, respectively. Such impressive photocatalytic activity is related to the synergeric effects derived from Ag, Ag3PO4, and Ti3C2, which greatly enhance visible light absorption, promote separation and transfer of photo-generated electron-hole pairs. This work highlights that the MXene-based photocatalysts would be desirable candidates for environmental purification of organic pollutants and heavy metal ions.

Manipulating photocatalytic pathway and activity of ternary Cu2O/(001)TiO2@Ti3C2Tx catalysts for H2 evolution: Effect of surface coverage

A Cu2O/(001)TiO2@Ti3C2Tx photocatalyst was synthesized via a wet-chemistry reduction method by N, N-dimethylformamide (DMF). By scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), it was revealed that the surface coverage of photocatalyst increased with the loading amount of Cu2O, while the particle size of Cu2O did not change significantly. The photocatalytic activity and mechanism of ternary Cu2O/(001)TiO2@Ti3C2Tx photocatalyst heavily depend on the surface coverage of copper species. When the surface coverage of photocatalyst by Cu2O was low, the Ti3C2Tx acted as hole reservoir. Cu2O was firstly reduced in situ to metallic copper by excited electrons. Then the reverse movement of carriers enabled the spatial separation of photogenerated electron-hole pairs, and afforded relatively high hydrogen evolution (more than 1100 μmol h−1 (g CuOx TiO2)−1). When the coverage of Cu2O on (001)TiO2@Ti3C2Tx was too high at high loading amounts, Ti3C2Tx failed to play the role of hole trapping. Under that circumstance, the photocatalytic reaction follows p-n junction mechanism, leading to low hydrogen productivity. The results here shed light on the relationship between structure and activity of Cu2O/(001)TiO2@Ti3C2Tx, which was conducive to the development of the MXene-based photocatalysts.