CO2 Photoreduction Activity Research Articles

Novel oxygen vacancy-enriched Bi2MoO6-x/MoS2 S-scheme heterojunction for strengthening photocatalytic reduction CO2 and efficient degradation of levofloxacin hydrochloride: Mechanism, DFT calculations

Constructing new photocatalysts for the photocatalytic reduction of CO2 and efficient degradation of Levofloxacin is of great importance to renewable energy. Here, S-scheme Bi2MoO6-x/MoS2 heterojunction nanospheres containing abundant surface defects (oxygen vacancies) were designed and successfully synthesized to enhance CO2 photoreduction activity in the absence of other sacrificial agents, co-catalysts or photosensitisers. At the same time, it can efficiently degrade organic pollutants (Levofloxacin). This heterogeneous structure with surface defects provides an abundance of reactive sites, accelerates charge separation and improves oxidation capacity. The improved Bi2MoO6-x/MoS2 heterogeneous nanospheres show excellent performance under simulated solar light, with the selectivity and yield of 92.45% and 29.01 µmol h−1, respectively, for the generation of CO. Under visible light, the degradation efficiency of levofloxacin hydrochloride (LVX) reached 96.3% within 25 min and remained as high as 95% after three cycles. This work provides a new idea for the design of new S-scheme photocatalysts and an important reference for the preparation of photocatalysts for the efficient photocatalytic reduction of CO2 and the efficient degradation of organic pollutants at the same time.

Interfacial Mo-S bond-reinforced hierarchical S-scheme heterostructure of Bi2MoO6@ZnIn2S4 for highly-selective and efficient CO2 photoreduction into CO

Developing highly-selective and efficient photocatalysts for converting CO2 into carbon-based fuels by solar energy is desirable, whereas it is still a severe challenge. Herein, we present a unique interfacial Mo-S bond-bridged hierarchical S-scheme heterostructured photocatalysts, prepared by in-situ loading ZnIn2S4 nanoflakes (ZIS-NFs) on the Bi2MoO6 porous micro-spheres (BMO-PMs) assembled from numerous nanosheets. The interfacial Mo-S bonds can reinforce the separation and migration of photoinduced charge carriers via the S-scheme mechanism in the BMO@ZIS heterostructure. Besides, its hierarchical heterostructure can improve the visible-light response ability, and afford plenty of active sites so as to benefit the CO2 adsorption and activation. Specifically, the combined results of experiment and density functional theory (DFT) calculations indicate that the fine heterostructure can not only convert the endoergic rate-determining step of bare ZIS (namely, CO2* hydrogenation to form COOH*) to an exoergic reaction process and lower the overall activation energy barrier, but also boost the desorption of CO* from the ZIS surface. As a result, in existence of H2O vapor without any sacrificial agents, the optimum photocatalyst (BMO@ZIS-0.4) manifests the outstanding CO2 photoreduction activity, with a CO yield and selectivity of 23.11 μmol g−1h−1 and 93.1 %, respectively, higher than those of the most reported photocatalysts. This work offers an in-depth insight for fabricating the interfacial chemical bond-modulated hierarchical S-scheme heterostructure with a remarkable performance of CO2 conversion.

Unveiling the effects of facet-dependent oxygen vacancy on CeO2 for electron structure and surface intermediates in CO2 photoreduction reaction

CO2 photoreduction over CeO2 surfaces has been studied for a few years, and many efforts have been devoted to understanding the effect of exposed crystal facets and oxygen vacancies (OVs) on the catalytic activity. In this work, the formation of OVs over different CeO2 surfaces is investigated through X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and electron paramagnetic resonance spectroscopy (EPR), revealing the facet-dependent OVsin CeO2. The experimental results and DFT calculations show that the OVs formed in (111)CeO2 and (100)CeO2 possess faster charge transfer and a more negative conduction band potential than (110)CeO2. The in-situ Fourier transform infrared spectroscopy (FTIR) and DFT results revealed the CO2 absorption, activation, and reduction processes over the three samples. Although (110)CeO2 surface shows the best adsorption capability for CO2, its catalytic activity is still limited by a high barrier (1.95 eV) in the formation of CO species from COOH* intermediate. Through the H2O-assisted CO2 activation process, (111)CeO2 and (100)CeO2 show better reduction activity for CO2, resulting in the better activity for CO2 photoreduction. This study demonstrates that the band structure and CO2 activation influenced by OVs show a strong crystal facet dependence in CeO2.

Multilevel-Regulated Metal-Organic Framework Platform Integrating Pore Space Partition and Open-Metal Sites for Enhanced CO2 Photoreduction to CO with Nearly 100% Selectivity.

Rational design and regulation of atomically precise photocatalysts are essential for constructing efficient photocatalytic systems tunable at both the atomic and molecular levels. Herein, we propose a platform-based strategy capable of integrating both pore space partition (PSP) and open-metal sites (OMSs) as foundational features for constructing high-performance photocatalysts. We demonstrate the first structural prototype obtained from this strategy: pore-partitioned NiTCPE-pstp (TCPE = 1,1,2,2-tetra(4-carboxylphenyl)ethylene, pstp = partitioned stp topology). Nonpartitioned NiTCPE-stp is constructed from six-connected [Ni3(μ3-OH)(COO)6] trimer and TCPE linker to form 1D hexagonal channels with six coplanar OMSs directed at channel centers. After introducing triangular pore-partitioning ligands, half of the OMSs were retained, while the other half were used for PSP, leading to unprecedented microenvironment regulation of the pore structure. The resulting material integrates multiple advanced properties, including robustness, wider absorption range, enhanced electronic conductivity, and high CO2 adsorption, all of which are highly desirable for photocatalytic applications. Remarkably, NiTCPE-pstp exhibits excellent CO2 photoreduction activity with a high CO generation rate of 3353.6 μmol g-1 h-1 and nearly 100% selectivity. Theoretical and experimental studies show that the introduction of partitioning ligands not only optimizes the electronic structure to promote the separation and transfer of photogenerated carriers but also reduces the energy barrier for the formation of *COOH intermediates while promoting CO2 activation and CO desorption. This work is believed to be the first example to integrate PSP strategies and OMSs within metal-organic framework (MOF) photocatalysts, which provides new insight as well as new structural prototype for the design and performance optimization of MOF-based photocatalysts.

Theoretical and experimental investigation of the coordination effect on photocatalytic CO2 reduction efficiency of cobalt single atom catalyst

Visible-light-driven carbon dioxide (CO2) reduction, which converts CO2 into value-added fuels, is an intriguing strategy to simultaneously mitigate the energy crisis and achieve a carbon–neutral economy. Single-atom catalysts (SACs) with homogeneously dispersed definite active sites and adjustable coordination environments show great potential in catalyzing photocatalytic CO2 reduction reaction (CO2RR). According to previously reported studies, the catalytic performance of SACs applied in various fields has a great relationship with their local coordination environment of metal centers. However, in-depth investigation of the coordination effect, which has been widely explored to regulate the electronic structure of SACs, on the activity, selectivity, and stability of CO2 photoreduction has never been reported. Herein, a series of Co single atom photocatalysts with diverse N coordination number (CoSA-Nx/C, x = 2, 3, and 4) were synthesized and their photocatalytic CO2RR performance was examined. Theoretical and experimental investigation demonstrated that the photocatalytic CO2RR activity of Co SACs can be effectively adjusted by fine-regulating the N coordination. The optimal CoSA-N2/C photocatalyst with two-coordinate N atoms with increased unoccupied Co 3d electronic orbitals possesses enhanced CO2 adsorption and activation as well as reduced energy barrier for *COOH intermediate generation, thus showing superior photoconversion of CO2-to-CO performance with 10110 μmol g−1h−1 CO evolution yield, 82.6 % CO selectivity, and long-term stability. This work promotes the future rationally design and synthesis of photocatalysts applied in targeted reactions at atomic scale.

CO2 Photoreduction Activity Enhancement and Unexpected Observation of Carbon Monoxide Adsorbates on the Surface of TiO2 Nanotube Arrays Synthesized in Formamide Electrolytes.

TiO2 nanotube arrays grown through electrochemical anodization in a formamide-based electrolyte (TNTA-FA) exhibited a whole host of unusual properties compared to nanotubes grown in the conventional ethylene glycol-based electrolyte (TNTA-EG). TNTA-FA exhibited shorter phonon lifetimes, lower lattice strain, more visible light absorption, lower work function, and a highly unusual adsorbate structure consisting of physisorbed and chemisorbed CO along with linearly adsorbed CO2 and various monodentate and bidentate carbonate species. The observation of adsorbed CO in the dark is highly unusual and indicates spontaneous deoxygenation of CO2 on the surface of TNTA-FA. The significance of this finding is that the formation of CO2•- is no longer the rate-limiting bottleneck for the reduction of CO2 on TNTA-FA surfaces as it is for all TiO2 surfaces. TNTA-FA samples are strongly colored (inclusive of a fluorescent green color) and consist of rounded, vertically oriented hollow cylinders as opposed to the honeycomb-like morphology of TNTA-EG arranged in an approximate triangular lattice. The photocatalytic activity was tested through the CO2 photoreduction and dye degradation tests. Formamide-based nanotubes outperformed the EG-based nanotubes by almost 1.7 and 2 times, respectively, in CO2 reduction and dye degradation tests done on methylene blue, brilliant green, and rhodamine B dyes. These results are attributed to stronger surface band bending in TNTA-FA which facilitates more efficient separation of photogenerated electron-hole pairs.

Highly selective photocatalytic CO2 reduction by metal-N4 dynamically generated from atomically dispersed copper

Solar-driven conversion of CO2 into high-value-added chemicals is considered as one of the effective strategies to address global climate change. However, the sluggish charge separation kinetics and poor product selectivity remain the two major bottlenecks restricting photocatalytic CO2 conversion. Herein, we developed an anatase surface modified atomically dispersed Cu (Cu anchored on N-doped carbon skeleton) photocatalyst (TiO2/Cu1NC) based on a “reflux + calcination” method for CO2 photoreduction. Under full spectral illumination, the as-synthesized TiO2/Cu1NC displayed a brilliant CO production rate of 2.59 μmol h−1 (mass of photocatalyst: 5 mg), high selectivity (∼98.5%), and excellent durability using [Ru(bpy)3]Cl2·6H2O as the photosensitizer and triethanolamine as an electron donor. Experiments and density functionalized theory calculations synergistically confirm that the surface-constructed atomically dispersed Cu1NC active sites can accelerate the separation and transfer of photogenerated charge carriers, optimize CO2 adsorption and activation, reduce the formation energy barrier of the key intermediate *COOH during the CO2RR process, and thus enhance the activity and selectivity of CO2RR. This work provides new insights into the surface engineering of atomically dispersed active sites to improve the activity and CO selectivity of CO2 photoreduction.

Highly stable lead-free perovskite Cs2AgBiBr6/UiO-66 Z-scheme heterostructures with enhanced photocatalytic activity for CO2 photoreduction and organic dyes degradation

Excessive combustion of traditional fossil fuels causes seriously global warming (Carbon dioxide, CO2) and energy crisis. Photocatalytic CO2 conversion to fuels has emerged as one of the most effective strategies. Herein, an environmentally friendly nanocomposite based on lead-free Cs2AgBiBr6 (CABB) perovskite nanocrystals and the UiO-66 metal–organic framework was fabricated by a facile ultrasonic process for efficient CO2 photoreduction. The obtained CABB/UiO-66 consisted of uniform CABB nanocrystals (10–12 nm) attached to the UiO-66 surface and exhibited a high surface area (1031 m2/g). The composite displayed enhanced light-harvesting capacity than the individual components and provided sufficient active sites for promoting photocatalytic activity. A typical Z-scheme heterostructure between the CABB and UiO-66 was realized by forming an inner electric field, leading to the occurrence of efficient excited state charge transfer. The efficient charge transfer of CABB/UiO-66 inspired its use as an active photocatalyst for the reduction of CO2 with significantly improved photocatalytic activity against its individual components. Specifically, CABB/UiO-66 exhibited 38 and 40-fold improvement in catalytic activity compared to respective CABB and UiO-66 in terms of the total yield of CO, CH4, and C2H6. Moreover, the nanocomposite displayed excellent activity towards the oxidative photocatalytic degradation of aqueous environmental contaminant rhodamine B. We believe that this work provides a guide for designing lead-free perovskite-based renewable catalysts and offers new opportunities for the photocatalytic conversion of CO2 photoreduction.

Photo-induced surface oxygen vacancy in hierarchical nanoarchitectonics g-C3N4/BiOCOOH to boost photocatalytic CO2 reduction

Photocatalytic CO2 conversion into chemical production and valuable solar fuel has been regarded as a prospective strategy for tackling with the issue of the global warming and energy crisis. A superior photocatalytic system employing heterojunction or oxygen vacancy (OVs) can facilitate efficient charge separation and transfer carriers. In this work, well-designed g-C3N4/BiOCOOH heterojunction microflowers assembly incorporated with abundant oxygen vacancy have been successfully synthesized via a mild photo irradiation treatment method. The BiOCOOH coupled with different amounts of g-C3N4 has an obviously impact on photocatalytic CO2 reduction into CO and CH4. Intriguingly, the as-obtained photo-induced oxygen vacancy g-C3N4/BiOCOOH-10 (CNB-10) show further enhanced CO yield towards photocatalytic CO2 reduction compared with pristine g-C3N4/BiOCOOH. Based on comprehensive characterization, the photo induced plenty of OVs in g-C3N4/BiOCOOH via UV light irradiation for 10 min could promote CO2 adsorption capacity as well as separation and transfer of photo-induced carriers, and significantly boost catalytic activity toward CO2 photoreduction. The elevated CO2 photoreduction activity of CNB-10 could be ascribed to the synergic effect of oxygen vacancy and S-scheme heterojunction structure on efficient carrier utilization and visible light absorption. This work can offer new perspectives and guidelines for the rational design of catalysts with satisfactory performance of CO2 reduction.

Zn-Cr Layered Double Hydroxides for Photocatalytic Transformation of CO2 under Visible Light Irradiation: The Effect of the Metal Ratio and Interlayer Anion

Carbon dioxide is the main gas responsible for the greenhouse effect. Over the last few years, the research focus of many studies has been to transform CO2 into valuable products (CO, HCOOH, HCHO, CH3OH and CH4), since it would contribute to mitigating global warming and environmental pollution. Layered double hydroxides (LDHs) are two-dimensional materials with high CO2 adsorption capacity and compositional flexibility with potential catalytic properties to be applied in CO2 reduction processes. Herein, Zn-Cr LDH-based materials with different metal ratio and interlayer anions, i.e., chloride (Cl−), graphene quantum dots (GQDs), sodium dodecyl sulfate (SDS) and sodium deoxycholate (SDC), have been prepared by a co-precipitation method and characterized by different techniques. The influence of the interlayer inorganic and organic anions and the metal ratio on the application of Zn-Cr LDHs as catalysts for the photocatalytic CO2 reduction reaction under visible light irradiation is unprecedentedly reported. The catalytic tests have been carried out with Ru(bpy)32+ as photosensitizer (PS) and triethanolamine as sacrificial electron donor (ED) at λ = 450 nm. All LDHs materials exhibited good photocatalytic activity towards CO. Among them, LDH3-SDC showed the best catalytic performance, achieving 10,977 µmol CO g−1 at 24 h under visible light irradiation with a CO selectivity of 88%. This study provides pertinent findings about the modified physicochemical features of Zn-Cr LDHs, such as particle size, surface area and the nature of the interlayer anion, and how they influence the catalytic activity in CO2 photoreduction.

Boosting CO2 Photoreduction via Regulating Charge Transfer Ability in a One‐Dimensional Covalent Organic Framework

AbstractTwo‐dimensional (2D) imine‐based covalent organic frameworks (COFs) hold potential for photocatalytic CO2 reduction. However, high energy barrier of imine linkage impede the in‐plane photoelectron transfer process, resulting in inadequate efficiency of CO2 photoreduction. Herein, we present a dimensionality induced local electronic modulation strategy through the construction of one‐dimensional (1D) pyrene‐based covalent organic frameworks (PyTTA‐COF). The dual‐chain‐like edge architectures of 1D PyTTA‐COF enable the stabilization of aromatic backbones, thus reducing energy loss during exciton dissociation and thermal relaxation, which provides energetic photoelectron to traverse the energy barrier of imine linkages. As a result, the 1D PyTTA‐COF exhibits significantly enhanced CO2 photoreduction activity under visible‐light irradiation when coordinated with metal cobalt ion, yielding a remarkable CO evolution of 1003 μmol g−1 over an 8‐hour period, which surpasses that of the corresponding 2D counterpart by a factor of 59. These findings present a valuable approach to address in‐plane charge transfer limitations in imine‐based COFs.

Boosting CO2 Photoreduction via Regulating Charge Transfer Ability in a One-Dimensional Covalent Organic Framework.

Two-dimensional (2D) imine-based covalent organic frameworks (COFs) hold potential for photocatalytic CO2 reduction. However, high energy barrier of imine linkage impede the in-plane photoelectron transfer process, resulting in inadequate efficiency of CO2 photoreduction. Herein, we present a dimensionality induced local electronic modulation strategy through the construction of one-dimensional (1D) pyrene-based covalent organic frameworks (PyTTA-COF). The dual-chain-like edge architectures of 1D PyTTA-COF enable the stabilization of aromatic backbones, thus reducing energy loss during exciton dissociation and thermal relaxation, which provides energetic photoelectron to traverse the energy barrier of imine linkages. As a result, the 1D PyTTA-COF exhibits significantly enhanced CO2 photoreduction activity under visible-light irradiation when coordinated with metal cobalt ion, yielding a remarkable CO evolution of 1003 μmol g-1 over an 8-hour period, which surpasses that of the corresponding 2D counterpart by a factor of 59. These findings present a valuable approach to address in-plane charge transfer limitations in imine-based COFs.

Valence state effect of Cu on photocatalytic CO2 reduction

Copper (Cu) is extensively employed in photocatalytic CO2 reduction reactions for the production of high-value products. The valence state of transition metals plays a pivotal role in influencing the catalytic process. However, due to the complex valence state changes of Cu in the CO2 reduction reaction, research on its valence state effect is lacking. The current work is to prepare a series of TiO2/CuX with stable Cu valence composition using different copper halides (CuX and CuX2, X = Br or Cl) as precursors. The results show that the CuBr2 loading leads to Cu+/Cu2+ mixed cocatalyst and exhibits the highest activity for CO2 photoreduction. The CH4 evolution rate of the TiO2/CuBr2 catalyst is as high as 100.59 μmol h−1 g−1, which is 6.6 times that of pristine TiO2. The CH4 selectivity reaches 77%. The enhanced catalytic activity and selectivity can be ascribed to the efficient surface adsorption, activation, excellent carrier separation, and transfer of Cu+/Cu2+ mixed cocatalyst. Our findings provide a reference for designing highly active Cu-based photocatalysts.

Enhancement in the Rate of CO2 Photoreduction Using Divalent Strontium Cation (Sr2+) Doped TiO2 Nanotube Arrays

We explored the selective surface doping of anodically formed TiO2 nanotube arrays (TNTAs) with divalent Sr2+ cations using an electrochemical cathodization process in order to modify the basicity of the surface and modify the interactions of the surface with vapor phase CO2. The resulting Sr-doped TNTAs showed a 3-fold increase in CO2 photoreduction activity. Characterization using a broad suite of bulk- and surface-sensitive characterization techniques revealed the doped Sr atoms to be widely dispersed on the surface. Our results show a way forward to achieve single atom catalysts using cathodic doping of TiO2.

Synergistic effect of surface modification and effective interfacial charge transfer over faceted g-C3N4/ZnSe heterojunction to enhance CO2 photoreduction activity

Heterojunction and surface modification are promising methods to boost the photocatalytic CO2 conversion efficiency which help to optimize the redox ability of photocatalysts and enhance the separation efficiency of photogenerated charge carriers. Herein, a novel surface-modified and interfacial heterojunction of g-C3N4 (CN) over a faceted ZnSe (ZS) {CN/ZS} composite was developed to accelerate the transfer of photogenerated electrons (e−) and holes (h+) between the CN and ZS photocatalysts. This technology allows faster transfer of a larger quantity of excited reductive electrons to the surface of ZS with a lower CO2 adsorption energy. Based on photocatalytic CO2 reduction to CO and CH4, 3 mmol CN/ZS composite outperformed all as-prepared photocatalysts including pure CN and ZS, with yielding rates of 439 and 203 umolg−1, respectively, with 88 % CO2 selectivity. The improved photocatalytic activity and selectivity were attributed to enhanced visible-light absorption, improved CO2 activation and adsorption on the surface of the photocatalyst and facilitated charge transfer at the interface. This study offers a novel approach for precisely controlling the direction of photogenerated charge separation by constructing a heterostructure for CO2 photoreduction.

Development of photocatalysts based on zeolite A with copper oxide (CuO) for application in the artificial photosynthesis process

This study explores the CO2 photoreduction process and its importance as a potential solution to mitigate carbon emissions. The co-precipitation method was used to produce composites formed between zeolite A and varying mass percentages of CuO, which demonstrated good activity and selectivity in CO2 photoreduction. The selectivity of the composites was linked to the presence of Lewis acid and base sites, with the predominance of Lewis base sites favoring the conversion of CO2 to CH4. Increased CuO content in the composite structure led to enhanced selectivity, reaching 100 % with ZE/CuO10 %. The presence of both Lewis acid and base sites facilitated the formation of two-carbon compounds such as ethylene, making the process of dimerization more accessible. Additionally, the study suggests that methanol and acetic acid can also be produced alongside other gaseous products such as CO, C2H4, and CH4. These findings highlight the potential of zeolite-based composites containing different active sites important during CO2 photoreduction for the production of valuable chemicals.

A metal-organic framework constructed by ferrocene and titanium clusters for CO2 photoreduction under visible light

As a promising photocatalyst, titanium-based metal organic framework (Ti-MOF) has been widely used for the photoreduction of CO2. In this paper, we developed a new Ti-MOF named Fe-Tc, constructed from titanium clusters and ferrocene. Fe-Tc had a wide absorbance range and a good response to visible light. Introducing ferrocene gave it good separation performance of photogenerated electrons and holes. What’s more, Fe-Tc showed excellent photocatalytic activity of CO2 photoreduction. Its production rate of formate (HCOO−) reached 39.5 μmol g−1 h−1 under visible light, which was better than some classical Ti-MOFs.

Dual Cu and S vacancies boost CO2 photomethanation on Cu1.95S1-x: Vacancy-regulated selective photocatalysis

Tuning product selectivity and improving activity are significant in CO2 photoreduction. Herein, we demonstrate that introducing Cu and S dual vacancies on copper sulfide surfaces can improve the CO2 photoreduction activity and completely switch the selectivity from CO to CH4. Experimental results reveal that Cu and S vacancies can attain a favorable CH4 production of 12.42 μmol g−1 h−1 with 100 % selectivity. Meanwhile, the single S vacancies also exhibit an approx. 4-fold CO yield (13.63 μmol g−1 h−1) compared with vacancy-free Cu2S (3.48 μmol g−1 h−1). Mechanism research indicates that the single S vacancies could promote the CO2 → COOH* → CO* pathway to improve the CO yield, while the simultaneously introducing of Cu and S dual vacancies can further lower the energy barriers of CO2 → COOH* → HCOOH* → CHO* pathway to promote the stepwise protonation of CO2, which in turn strengthen the selectivity of CO2-to-CH4 photoreduction.

Promoting CO2 and H2O activation on O-vacancy regulated In-Ti dual-sites for enhanced CH4 photo-production

Engineering the specific active sites of photocatalysts for simultaneously promoting CO2 and H2O activation is important to achieve the efficient conversion of CO2 to hydrocarbon with H2O as a proton source under sunlight. Herein, we delicately design the In/TiO2-VO photocatalyst by engineering In single atoms (SAs) and oxygen vacancies (VOs) on porous TiO2. The relation between structure and performance of the photocatalyst is clarified by both experimental and theoretical analyses at the atomic levels. The In/TiO2-VO photocatalyst furnish a high CH4 production rate up to 35.49 μmol g−1 h−1 with a high selectivity of 91.3% under simulated sunlight, while only CO is sluggishly generated on TiO2-VO. The combination of in situ spectroscopic analyses with theoretical calculations reveal that the VO sites accelerate H2O dissociation and increase proton feeding for CO2 reduction. Furthermore, the VO regulated In-Ti dual sites enable the formation of a stable adsorption conformation of In-C-O-Ti intermediate, which is responsible for the highly selective reduction of CO2 to CH4. This work demonstrates a new strategy for the development of effective photocatalysts by coupling metal SA sites with the adjacent metal sites of support to synergistically enhance the activity and selectivity of CO2 photoreduction.

Cu-doped monoclinic WO3 nanoplates with superior photocatalytic activity for CO2 photoreduction

Cu-doped monoclinic WO3 nanoplates with superior photocatalytic activity for CO2 photoreduction