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2025 Volume 41 Issue 11
2025, 41(11): 100146
doi: 10.1016/j.actphy.2025.100146
Abstract:
2025, 41(11): 100150
doi: 10.1016/j.actphy.2025.100150
Abstract:
Tandem S-scheme heterojunctions have emerged as a highly promising innovation in photocatalysis, offering an effective solution for environmental remediation. Unlike traditional Z-scheme or type-Ⅱ photocatalysts, the S-scheme architecture selectively retains high-energy photocarriers that actively participate in redox reactions. This unique mechanism enhances charge separation, strengthens internal electric fields, and enhance light absorption. However, the single junction of S-scheme suffers from low quantum efficiency. Therefore, engineering a multicomponent system with S-scheme effectively improve the photocatalytic properties. Tandem S-scheme systems consist of multiple semiconductors/materials with staggered energy band positions to create a stepwise or directional charge transferal mechanism. This stepwise potential gradient is responsible for more enhanced charge separation, light absorption, redox ability, stability, and overall photocatalytic activity. This article provides an in-depth overview of the principles governing tandem S-scheme heterojunctions, discussing the design of tandem S-scheme heterojunctions through semiconductor pairing, co-catalyst addition, and mediator inclusion for maximum charge mobility and minimum recombination. The various synthesis pathways are explored along with the kinetics and thermodynamics of tandem S-scheme heterojunction. A range of advanced characterization tools, including density functional theory (DFT) simulations, in situ X-ray photoelectron spectroscopy (XPS), transient absorption spectroscopy (TAS), photoluminescence (PL), and electrochemical impedance spectroscopy (EIS) studies are discussed, which together offer valuable insight into electronic behaviours and interfacial dynamics. Applications of these heterojunctions are discussed across major domains such as carbon dioxide reduction, H2 evolution, and degradation of organic pollutants. While the potential is clear, challenges such as complex synthesis procedures, material stability, and scalability still need to be addressed. To overcome the limitations, the article suggests future research paths. Overall, tandem S-scheme heterojunctions stand out as an excellent approach for building efficient and sustainable photocatalytic technologies.![]()
Tandem S-scheme heterojunctions have emerged as a highly promising innovation in photocatalysis, offering an effective solution for environmental remediation. Unlike traditional Z-scheme or type-Ⅱ photocatalysts, the S-scheme architecture selectively retains high-energy photocarriers that actively participate in redox reactions. This unique mechanism enhances charge separation, strengthens internal electric fields, and enhance light absorption. However, the single junction of S-scheme suffers from low quantum efficiency. Therefore, engineering a multicomponent system with S-scheme effectively improve the photocatalytic properties. Tandem S-scheme systems consist of multiple semiconductors/materials with staggered energy band positions to create a stepwise or directional charge transferal mechanism. This stepwise potential gradient is responsible for more enhanced charge separation, light absorption, redox ability, stability, and overall photocatalytic activity. This article provides an in-depth overview of the principles governing tandem S-scheme heterojunctions, discussing the design of tandem S-scheme heterojunctions through semiconductor pairing, co-catalyst addition, and mediator inclusion for maximum charge mobility and minimum recombination. The various synthesis pathways are explored along with the kinetics and thermodynamics of tandem S-scheme heterojunction. A range of advanced characterization tools, including density functional theory (DFT) simulations, in situ X-ray photoelectron spectroscopy (XPS), transient absorption spectroscopy (TAS), photoluminescence (PL), and electrochemical impedance spectroscopy (EIS) studies are discussed, which together offer valuable insight into electronic behaviours and interfacial dynamics. Applications of these heterojunctions are discussed across major domains such as carbon dioxide reduction, H2 evolution, and degradation of organic pollutants. While the potential is clear, challenges such as complex synthesis procedures, material stability, and scalability still need to be addressed. To overcome the limitations, the article suggests future research paths. Overall, tandem S-scheme heterojunctions stand out as an excellent approach for building efficient and sustainable photocatalytic technologies.
2025, 41(11): 100132
doi: 10.1016/j.actphy.2025.100132
Abstract:
Photocatalytic CO2 reduction under atmospheric concentrations remains highly challenging yet critical for practical carbon-neutral applications. In this study, a Cu-loaded, carbon-doped boron nitride (Cu/BCN) photocatalyst was synthesized by a microwave-assisted molten salt method. This approach enables simultaneous carbon incorporation into the BN lattice and selective deposition of Cu nanoparticles, forming an efficient heterostructure. The synergy between C doping and Cu loading modulates the band structure, enhances visible-light absorption, promotes charge separation, and improves CO2 adsorption. The optimized Cu/BCN photocatalyst achieved a CO production rate of 30.62 μmol·g−1·h−1 with 95.8% selectivity under ambient CO2 conditions. Combined experimental and DFT analyses confirm that the Cu/BCN interface facilitates charge transfer and lowers the energy barrier for *COOH formation. This work demonstrates a promising route toward efficient CO2 utilization directly from air, offering a scalable strategy for atmospheric carbon conversion.![]()
Photocatalytic CO2 reduction under atmospheric concentrations remains highly challenging yet critical for practical carbon-neutral applications. In this study, a Cu-loaded, carbon-doped boron nitride (Cu/BCN) photocatalyst was synthesized by a microwave-assisted molten salt method. This approach enables simultaneous carbon incorporation into the BN lattice and selective deposition of Cu nanoparticles, forming an efficient heterostructure. The synergy between C doping and Cu loading modulates the band structure, enhances visible-light absorption, promotes charge separation, and improves CO2 adsorption. The optimized Cu/BCN photocatalyst achieved a CO production rate of 30.62 μmol·g−1·h−1 with 95.8% selectivity under ambient CO2 conditions. Combined experimental and DFT analyses confirm that the Cu/BCN interface facilitates charge transfer and lowers the energy barrier for *COOH formation. This work demonstrates a promising route toward efficient CO2 utilization directly from air, offering a scalable strategy for atmospheric carbon conversion.
2025, 41(11): 100133
doi: 10.1016/j.actphy.2025.100133
Abstract:
In the realm of photocatalytic CO2 hydrogenation, the adsorption-desorption behaviors and dynamics of photogenerated carriers are pivotal determinants of the kinetic processes and overall efficiency of photocatalytic reactions. Herein, 5A molecular sieve-functionalized In2O3 composites (denoted as IO@5A-xwt%) were fabricated through a facile impregnation-calcination method. Among them, the IO@5A-5wt% composite, with the optimized loading amount of 5A molecular sieves, showcases outstanding performance in photocatalytic conversion of CO2 to CO, achieving a CO production rate of 2610.55 μmol·g−1·h−1, which is 19 times higher than that of pristine In2O3. Moreover, the IO@5A-5wt% composite maintains acceptable catalytic stability after a prolonged experiment lasting 45 h and total of 108 cycles. A comprehensive series of characterization techniques and performance evaluations reveal that the incorporation of 5A molecular sieves significantly modulates the adsorption-desorption behavior and hole dynamics during photocatalytic reactions. The multi-channel architecture of 5A molecular sieves, featuring suitable pore sizes, effectively enhances CO2 adsorption. Meanwhile, the surface hydroxyl groups of 5A molecular sieves facilitate the transfer of photogenerated holes, thereby suppressing the recombination of photogenerated carriers. Additionally, the reaction product H2O desorbs more readily from the catalyst surface. These synergistic effects collectively constitute the key mechanism underlying the enhanced photocatalytic performance of the IO@5A-5wt% composite. ![]()
In the realm of photocatalytic CO2 hydrogenation, the adsorption-desorption behaviors and dynamics of photogenerated carriers are pivotal determinants of the kinetic processes and overall efficiency of photocatalytic reactions. Herein, 5A molecular sieve-functionalized In2O3 composites (denoted as IO@5A-xwt%) were fabricated through a facile impregnation-calcination method. Among them, the IO@5A-5wt% composite, with the optimized loading amount of 5A molecular sieves, showcases outstanding performance in photocatalytic conversion of CO2 to CO, achieving a CO production rate of 2610.55 μmol·g−1·h−1, which is 19 times higher than that of pristine In2O3. Moreover, the IO@5A-5wt% composite maintains acceptable catalytic stability after a prolonged experiment lasting 45 h and total of 108 cycles. A comprehensive series of characterization techniques and performance evaluations reveal that the incorporation of 5A molecular sieves significantly modulates the adsorption-desorption behavior and hole dynamics during photocatalytic reactions. The multi-channel architecture of 5A molecular sieves, featuring suitable pore sizes, effectively enhances CO2 adsorption. Meanwhile, the surface hydroxyl groups of 5A molecular sieves facilitate the transfer of photogenerated holes, thereby suppressing the recombination of photogenerated carriers. Additionally, the reaction product H2O desorbs more readily from the catalyst surface. These synergistic effects collectively constitute the key mechanism underlying the enhanced photocatalytic performance of the IO@5A-5wt% composite.
2025, 41(11): 100136
doi: 10.1016/j.actphy.2025.100136
Abstract:
Coupling H2O2 production with organic pollutant degradation can effectively overcome the sluggish kinetics of water oxidation while concurrently addressing environmental pollution challenges. In this work, an S-defect-rich ZnIn2S4/g-C3N4 (ZIS1−x/UCN) S-scheme heterojunction photocatalyst was constructed by in situ growing ZIS1−x nanosheets on porous ultrathin UCN. The designed ZIS1−x/UCN photocatalyst demonstrates enhanced visible light absorption, abundant active sites, and intimate interfacial contact. The optimized ZIS1−x/UCN-1.0 photocatalyst exhibits outstanding dual functionality, simultaneously achieving an H2O2 production rate of 2902.2 µmol·g−1·h−1 and 91.3% tetracycline (50 mg·L−1) degradation efficiency. This H2O2 performance represents a 1.63-fold enhancement compared to its activity in pure water (1777.0 µmol·g−1·h−1). Through comprehensive characterization including femtosecond transient absorption spectroscopy (fs-TAS), in situ irradiation X-ray photoelectron spectroscopy (ISI-XPS), and in situ X-ray absorption fine structure spectroscopy (XAFS), we unequivocally confirm the S-scheme charge transfer mechanism. This S-scheme induced unique electronic structure not only fosters ultrafast electron transfer at the interface (3.54 ps) but also significantly enhances the redox capacity of photogenerated carriers. Collectively, this work opens new avenues for the dual application of photocatalytic technology in both energy production and environmental remediation. ![]()
Coupling H2O2 production with organic pollutant degradation can effectively overcome the sluggish kinetics of water oxidation while concurrently addressing environmental pollution challenges. In this work, an S-defect-rich ZnIn2S4/g-C3N4 (ZIS1−x/UCN) S-scheme heterojunction photocatalyst was constructed by in situ growing ZIS1−x nanosheets on porous ultrathin UCN. The designed ZIS1−x/UCN photocatalyst demonstrates enhanced visible light absorption, abundant active sites, and intimate interfacial contact. The optimized ZIS1−x/UCN-1.0 photocatalyst exhibits outstanding dual functionality, simultaneously achieving an H2O2 production rate of 2902.2 µmol·g−1·h−1 and 91.3% tetracycline (50 mg·L−1) degradation efficiency. This H2O2 performance represents a 1.63-fold enhancement compared to its activity in pure water (1777.0 µmol·g−1·h−1). Through comprehensive characterization including femtosecond transient absorption spectroscopy (fs-TAS), in situ irradiation X-ray photoelectron spectroscopy (ISI-XPS), and in situ X-ray absorption fine structure spectroscopy (XAFS), we unequivocally confirm the S-scheme charge transfer mechanism. This S-scheme induced unique electronic structure not only fosters ultrafast electron transfer at the interface (3.54 ps) but also significantly enhances the redox capacity of photogenerated carriers. Collectively, this work opens new avenues for the dual application of photocatalytic technology in both energy production and environmental remediation.
2025, 41(11): 100137
doi: 10.1016/j.actphy.2025.100137
Abstract:
Mo2C MXene (Mo2CTx) exhibits exceptional hydrogen-evolution potential in photocatalysis due to the Pt-like electronic structure of surface Mo active sites. However, the Mo sites in Mo2CTx usually show excessively strong H-adsorption during HER, significantly limiting the intrinsic catalytic activity of Mo2CTx. To weaken the H-adsorption capacity of Mo active sites, a strategy of modulating d-orbital electron is implemented via in-situ constructing MoC-Mo2C MXene heterojunction by a work-function-induced effect. The MoC-Mo2CTx heterojunction was synthesized by in situ conversion of Mo2C MXene into MoC via a Co-induced molten salt method, followed by coupling with TiO2 through a simple ultrasonication-assisted method to prepare the MoC-Mo2CTx/TiO2 photocatalyst. Photocatalytic tests showed that the optimal MoC-Mo2CTx/TiO2 sample achieves an excellent hydrogen production rate of 1886 μmol∙h−1∙g−1, representing 117.9 and 3.9 fold enhancements over TiO2 and Mo2CFX/TiO2 (Mo2CF2 prepared by a conventional etchant NH4F+HCl), respectively. Experimental and theoretical calculations substantiate that the work-function gradient between MoC and Mo2C MXene induces electron transfer from MoC to Mo2C MXene to weaken the H-adsorption of Mo active sites in Mo2CTx cocatalyst, thereby enhancing its HER activity. This research provides a new strategy of in situ constructing Mo2C MXene-based heterojunction for adjusting the H-adsorption capacity of Mo active sites. ![]()
Mo2C MXene (Mo2CTx) exhibits exceptional hydrogen-evolution potential in photocatalysis due to the Pt-like electronic structure of surface Mo active sites. However, the Mo sites in Mo2CTx usually show excessively strong H-adsorption during HER, significantly limiting the intrinsic catalytic activity of Mo2CTx. To weaken the H-adsorption capacity of Mo active sites, a strategy of modulating d-orbital electron is implemented via in-situ constructing MoC-Mo2C MXene heterojunction by a work-function-induced effect. The MoC-Mo2CTx heterojunction was synthesized by in situ conversion of Mo2C MXene into MoC via a Co-induced molten salt method, followed by coupling with TiO2 through a simple ultrasonication-assisted method to prepare the MoC-Mo2CTx/TiO2 photocatalyst. Photocatalytic tests showed that the optimal MoC-Mo2CTx/TiO2 sample achieves an excellent hydrogen production rate of 1886 μmol∙h−1∙g−1, representing 117.9 and 3.9 fold enhancements over TiO2 and Mo2CFX/TiO2 (Mo2CF2 prepared by a conventional etchant NH4F+HCl), respectively. Experimental and theoretical calculations substantiate that the work-function gradient between MoC and Mo2C MXene induces electron transfer from MoC to Mo2C MXene to weaken the H-adsorption of Mo active sites in Mo2CTx cocatalyst, thereby enhancing its HER activity. This research provides a new strategy of in situ constructing Mo2C MXene-based heterojunction for adjusting the H-adsorption capacity of Mo active sites.
2025, 41(11): 100142
doi: 10.1016/j.actphy.2025.100142
Abstract:
Photocatalytic oxygen reduction reaction (ORR) offers a mild and cost-effective approach for hydrogen peroxide (H2O2) production. However, its practical application is significantly hindered by rapid charge carrier recombination and insufficient O2 adsorption capacity in photocatalysts. To address these limitations, we developed a strategy involving the creation of S-vacancy-rich CdIn2S4 (Sv–CIS) to facilitate charge separation and subsequent deposition of Au nanoparticles on its surface (Au–Sv–CIS) to strengthen O2 adsorption. The results suggest that the optimized Au–Sv–CIS achieves a significantly increased H2O2 production yield of 2542 μmol·h−1·g−1 in 10%-ethanol/water solution, which is about 12.8 and 1.7 times higher than that of pure CIS and Sv–CIS. Comprehensive characterizations including photoluminescence spectra, time-resolved photoluminescence spectra, transient photocurrent response, electrochemical impedance spectra, and femtosecond transient absorption spectroscopy confirm the improved charge dynamics of Au–Sv–CIS. In addition, temperature-programmed desorption of O2 combined with density functional theory calculations conclusively demonstrates the superior O2 adsorption capacity of Au–Sv–CIS. This work provides a design strategy for efficient solar-to-chemical energy conversion through cooperative photocatalyst engineering. ![]()
Photocatalytic oxygen reduction reaction (ORR) offers a mild and cost-effective approach for hydrogen peroxide (H2O2) production. However, its practical application is significantly hindered by rapid charge carrier recombination and insufficient O2 adsorption capacity in photocatalysts. To address these limitations, we developed a strategy involving the creation of S-vacancy-rich CdIn2S4 (Sv–CIS) to facilitate charge separation and subsequent deposition of Au nanoparticles on its surface (Au–Sv–CIS) to strengthen O2 adsorption. The results suggest that the optimized Au–Sv–CIS achieves a significantly increased H2O2 production yield of 2542 μmol·h−1·g−1 in 10%-ethanol/water solution, which is about 12.8 and 1.7 times higher than that of pure CIS and Sv–CIS. Comprehensive characterizations including photoluminescence spectra, time-resolved photoluminescence spectra, transient photocurrent response, electrochemical impedance spectra, and femtosecond transient absorption spectroscopy confirm the improved charge dynamics of Au–Sv–CIS. In addition, temperature-programmed desorption of O2 combined with density functional theory calculations conclusively demonstrates the superior O2 adsorption capacity of Au–Sv–CIS. This work provides a design strategy for efficient solar-to-chemical energy conversion through cooperative photocatalyst engineering.
2025, 41(11): 100145
doi: 10.1016/j.actphy.2025.100145
Abstract:
Developing highly efficient photocatalysts with a full-spectrum response for hydrogen production is of great significance. To achieve full-spectrum solar-light-driven photocatalysis, W18O49 works well for capturing visible and near-infrared (NIR) light due to the localized surface plasmon resonances (LSPR) effect. Nevertheless, W18O49 has very little photocatalytic hydrogen generation activity, which needs to be modified. In this work, a simple in situ solvothermal synthesis method was conducted to prepare Al-doped SrTiO3 (ASTO)/W18O49 S-scheme heterojunction. Benefiting from more powerful carrier separation, faster electron transport, and strong redox capacity, the 10% ASTO/W18O49 S-scheme heterojunction exhibits the highest full-spectrum solar-light-driven photocatalytic hydrogen rate, which is 17.5 and 27.6 times that of pure ASTO and W18O49, respectively. The LSPR effect derived from W18O49 with abundant oxygen vacancies extends the range of light absorption to the NIR region, which significantly improves its utilization efficiency of full-spectrum sunlight. Moreover, due to the LSPR effect of W18O49, it could produce plasmonic high-energy "hot electrons" and allow them to transfer to the conduction band (CB) of ASTO in the ASTO/W18O49 heterojunction, which could promote the separation and migration of photoinduced carriers and greatly increase the number of electrons containing photogenerated electrons and "hot electrons" on the CB of ASTO that can participate in photocatalytic hydrogen production reaction, exhibiting excellent photocatalytic hydrogen evolution performance compared to single-component W18O49 and ASTO.![]()
Developing highly efficient photocatalysts with a full-spectrum response for hydrogen production is of great significance. To achieve full-spectrum solar-light-driven photocatalysis, W18O49 works well for capturing visible and near-infrared (NIR) light due to the localized surface plasmon resonances (LSPR) effect. Nevertheless, W18O49 has very little photocatalytic hydrogen generation activity, which needs to be modified. In this work, a simple in situ solvothermal synthesis method was conducted to prepare Al-doped SrTiO3 (ASTO)/W18O49 S-scheme heterojunction. Benefiting from more powerful carrier separation, faster electron transport, and strong redox capacity, the 10% ASTO/W18O49 S-scheme heterojunction exhibits the highest full-spectrum solar-light-driven photocatalytic hydrogen rate, which is 17.5 and 27.6 times that of pure ASTO and W18O49, respectively. The LSPR effect derived from W18O49 with abundant oxygen vacancies extends the range of light absorption to the NIR region, which significantly improves its utilization efficiency of full-spectrum sunlight. Moreover, due to the LSPR effect of W18O49, it could produce plasmonic high-energy "hot electrons" and allow them to transfer to the conduction band (CB) of ASTO in the ASTO/W18O49 heterojunction, which could promote the separation and migration of photoinduced carriers and greatly increase the number of electrons containing photogenerated electrons and "hot electrons" on the CB of ASTO that can participate in photocatalytic hydrogen production reaction, exhibiting excellent photocatalytic hydrogen evolution performance compared to single-component W18O49 and ASTO.
2025, 41(11): 100147
doi: 10.1016/j.actphy.2025.100147
Abstract:
This study presents an innovative photocatalytic system utilizing waste biomass resources for sustainable synthesis of hydrogen peroxide (H2O2) and high-value lignin derivatives. A lignin derived carbon quantum dots (LCQDs) loaded S-scheme heterojunction photocatalyst LCQDs/Bi2WO6 (LCD/BWO) was synthesized via hydrothermal method. The LCD/BWO composite demonstrates exceptional H2O2 production rate (3.776 mmol·h−1·g−1) and maintains 89.72% activity retention after 5 cycles under visible light irradiation, representing a 5.97-fold enhancement over catalyst BWO−A. The performance leap stems from synergistic effects between LCQDs and oxygen vacancies (OVs) defects: the unique up-conversion luminescence of LCQDs combined with S-scheme charge transfer mechanism enhances light absorption and carrier separation efficiency, while interfacial OVs act as electron traps to prolong carrier lifetime. In situ electron paramagnetic resonance (In situ EPR) analysis revealed substantial generation of •O2⁻ and •OH radicals on catalyst surfaces. Band structure characterization confirms optimized H2O2 synthesis through consecutive single-electron reactions. Synergistic regulation of band positions significantly enhances oxygen reduction reaction (ORR) and water oxidation reaction (WOR) capabilities. As lignin primarily originates from agricultural/forestry waste, this work not only provides new design strategies for efficient photocatalytic systems but also advances high−value utilization of waste biomass resources.![]()
This study presents an innovative photocatalytic system utilizing waste biomass resources for sustainable synthesis of hydrogen peroxide (H2O2) and high-value lignin derivatives. A lignin derived carbon quantum dots (LCQDs) loaded S-scheme heterojunction photocatalyst LCQDs/Bi2WO6 (LCD/BWO) was synthesized via hydrothermal method. The LCD/BWO composite demonstrates exceptional H2O2 production rate (3.776 mmol·h−1·g−1) and maintains 89.72% activity retention after 5 cycles under visible light irradiation, representing a 5.97-fold enhancement over catalyst BWO−A. The performance leap stems from synergistic effects between LCQDs and oxygen vacancies (OVs) defects: the unique up-conversion luminescence of LCQDs combined with S-scheme charge transfer mechanism enhances light absorption and carrier separation efficiency, while interfacial OVs act as electron traps to prolong carrier lifetime. In situ electron paramagnetic resonance (In situ EPR) analysis revealed substantial generation of •O2⁻ and •OH radicals on catalyst surfaces. Band structure characterization confirms optimized H2O2 synthesis through consecutive single-electron reactions. Synergistic regulation of band positions significantly enhances oxygen reduction reaction (ORR) and water oxidation reaction (WOR) capabilities. As lignin primarily originates from agricultural/forestry waste, this work not only provides new design strategies for efficient photocatalytic systems but also advances high−value utilization of waste biomass resources.
2025, 41(11): 100148
doi: 10.1016/j.actphy.2025.100148
Abstract:
The conversion of CO2 into value-added hydrocarbons via photocatalysis holds great promise for sustainable energy, yet achieving high activity and selectivity remains challenging. Herein, a novel TiO2/CdS heterostructured photocatalyst exhibits exceptional performance in CO2 photoreduction. The optimized catalyst delivers a 4.2-fold increase in CH4 production rate compared to pristine TiO2, with a remarkable 65.4% selectivity toward CH4 (34.6% CO). The enhanced activity arises from the unique morphology, facilitating CO2 adsorption and mass transfer, and the intimate S-scheme heterojunction between CdS and TiO2, which boosts charge separation while preserving strong redox potentials. Critically, femtosecond transient absorption spectroscopy (fs-TAS) combined with in situ DRIFTS provides direct evidence for the S-scheme pathway and identifies sulfur sites on CdS as key for stabilizing *CH3O, *CHO and *CO intermediates, steering selectivity toward CH4. In addition, theoretical calculations based on density functional theory (DFT) further complement the experimental findings. The calculations confirm the electronic structure characteristics of the S-scheme heterojunction, revealing the energy levels and charge transfer mechanisms at the atomic scale. This not only deepens our understanding of the photocatalytic process but also provides a theoretical basis for further optimizing the photocatalyst design. Overall, our work demonstrates the outstanding performance of the TiO2/CdS heterostructured photocatalyst in CO2 photoreduction.![]()
The conversion of CO2 into value-added hydrocarbons via photocatalysis holds great promise for sustainable energy, yet achieving high activity and selectivity remains challenging. Herein, a novel TiO2/CdS heterostructured photocatalyst exhibits exceptional performance in CO2 photoreduction. The optimized catalyst delivers a 4.2-fold increase in CH4 production rate compared to pristine TiO2, with a remarkable 65.4% selectivity toward CH4 (34.6% CO). The enhanced activity arises from the unique morphology, facilitating CO2 adsorption and mass transfer, and the intimate S-scheme heterojunction between CdS and TiO2, which boosts charge separation while preserving strong redox potentials. Critically, femtosecond transient absorption spectroscopy (fs-TAS) combined with in situ DRIFTS provides direct evidence for the S-scheme pathway and identifies sulfur sites on CdS as key for stabilizing *CH3O, *CHO and *CO intermediates, steering selectivity toward CH4. In addition, theoretical calculations based on density functional theory (DFT) further complement the experimental findings. The calculations confirm the electronic structure characteristics of the S-scheme heterojunction, revealing the energy levels and charge transfer mechanisms at the atomic scale. This not only deepens our understanding of the photocatalytic process but also provides a theoretical basis for further optimizing the photocatalyst design. Overall, our work demonstrates the outstanding performance of the TiO2/CdS heterostructured photocatalyst in CO2 photoreduction.
2025, 41(11): 100153
doi: 10.1016/j.actphy.2025.100153
Abstract:
The selective oxidation of methane to value-added chemicals under mild conditions presents a sustainable yet challenging route, hindered by sluggish CH4 activation and overoxidation. Herein, we report a delicate strategy combining Ti doping and Au loading to construct a high-performance Au/Ti−CeO2 photocatalyst for ethane production from oxidative methane coupling. The optimized catalyst achieves a C2H6 production rate of 2971.4 μmol·g−1·h−1 with 85.1% C2+ selectivity, stably operating over 20 reaction cycles. In situ X-ray photoelectron spectroscopy, electron paramagnetic resonance, and diffuse reflectance infrared Fourier transform spectroscopy analyses reveal that Ti doping introduces impurity energy levels into CeO2, promoting directional electron migration to surface Au nanoparticles (NPs) via a built-in electric field. The Au NPs act as electron accumulation sites to activate O2, facilitate *CH3 radical coupling into C2H6, and stabilize reactive intermediates, thus enhancing charge separation and suppressing intermediate overoxidation. This study highlights the significance of synergistic modulation via elemental doping and cocatalyst engineering in tuning charge dynamics and surface reactivity for efficient photocatalytic methane conversion.![]()
The selective oxidation of methane to value-added chemicals under mild conditions presents a sustainable yet challenging route, hindered by sluggish CH4 activation and overoxidation. Herein, we report a delicate strategy combining Ti doping and Au loading to construct a high-performance Au/Ti−CeO2 photocatalyst for ethane production from oxidative methane coupling. The optimized catalyst achieves a C2H6 production rate of 2971.4 μmol·g−1·h−1 with 85.1% C2+ selectivity, stably operating over 20 reaction cycles. In situ X-ray photoelectron spectroscopy, electron paramagnetic resonance, and diffuse reflectance infrared Fourier transform spectroscopy analyses reveal that Ti doping introduces impurity energy levels into CeO2, promoting directional electron migration to surface Au nanoparticles (NPs) via a built-in electric field. The Au NPs act as electron accumulation sites to activate O2, facilitate *CH3 radical coupling into C2H6, and stabilize reactive intermediates, thus enhancing charge separation and suppressing intermediate overoxidation. This study highlights the significance of synergistic modulation via elemental doping and cocatalyst engineering in tuning charge dynamics and surface reactivity for efficient photocatalytic methane conversion.
