Photocatalytic Conversion Of Carbon Dioxide Research Articles

Enhanced selective photocatalytic CO2 reduction to CO on AuPd decorated Bi2O2.33 nanosheets

Photocatalytic conversion of carbon dioxide (CO2) into valuable fuels addresses pressing needs for renewable energy and carbon neutrality. However, conventional photocatalytic CO2 reduction on semiconductor is usually limited by sluggish electron kinetics, poor efficiency and low product selectivity. Herein, we developed a bimetallic Au/Pd-decorated Bi2O2.33 ultrathin nanosheet photocatalyst for highly selective CO2 reduction to CO under visible light irradiation. Bi2O2.33 nanosheets self-assembled from nanodots serve as ideal supports for Au/Pd anchoring due to abundant grain boundaries. Systematic characterization reveals the formation of alloyed Au/Pd nanoparticles on the Bi2O2.33 surface, which endowed a superior CO production rate of 436.8 μmol g−1 h−1 with a selectivity of 96.68 % from CO2 photoreduction. Quantum chemical calculations uncover that plasmonic Au/Pd alloys facilitates interfacial charge transfer and CO2 activation to form the CO-yielding intermediate. This work demonstrates an effective strategy for designing bimetallic plasmonic cocatalysts to optimize the photoreduction selectivity and efficiency of semiconductor photocatalysts.

Amorphous Metallic Cobalt-Based Organophosphonic Acid Compounds as Novel Photocatalysts to Boost Photocatalytic CO2 Reduction

Photocatalytic carbon dioxide conversion is a promising method for generating carbon fuels, in which the most important thing is to adjust the catalyst material to improve the photocatalytic efficiency and selectivity to conversion products, but it is still very challenging. In order to enhance the efficiency of CO2 photoreduction, it is important to develop an appropriate photocatalyst. The present study focuses on developing a simple and effective hydrothermal reaction treatment to improve the catalytic efficiency of transition metal cobalt (Co) and organophosphonates. Photoexcited charge carriers are separated and transferred efficiently during this treatment, which enhances CO2 chemisorption. Under visible light exposure, the best performing catalyst, CoP-4, showed 2.4 times higher activity than Co3O4 (19.90 μmol h−1 g−1) for reducing CO2 into CO, with rates up to 47.16 μmol h−1 g−1. This approach provides a viable route to enhancing the efficiency of CO2 photoreduction.

PdCu alloy anchored defective titania for photocatalytic conversion of carbon dioxide into methane with 100% selectivity

The photoreduction of CO2 into CH4 with simultaneous high activity and selectivity is a promising strategy to increase energy supply and alleviate global warming. However, the absence of the active sites that is responsible for the adsorption and activation of CO2 and the generation of CO and H2 via side reactions often lead to poor efficiency and low selectivity of the catalyst. Herein, Cu, Pd, and PdCu metal clusters cocatalyst-anchored defective TiO2 nanotubes (Cu/TiO2-SBO, Pd/TiO2-SBO, and Pd1Cu1/TiO2-SBO) were designed via a simple solution impregnation reduction and applied for photocatalytic conversion of CO2 to CH4. The Pd1Cu1/TiO2-SBO photocatalyst exhibits excellent catalytic performance among the other catalysts for photoreduction of CO2 into CH4. More interestingly, the product selectivity of CH4 reaches up to 100% with a rate of 25 µmol g−1 h−1. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) simulations indicate that the main reasons for the high selectivity of CH4 are attributed to the PdCu alloy and oxygen vacancies, which jointly enhance the photoinduced carrier separation and lower energy barriers of key intermediates. Moreover, due to the tunable d-band center of the Cu site in the PdCu alloy, the generated intermediates can be well prevented from poisoning and promoted to participate in further reactions. Hopefully, the current study will provide insight into the development of new, highly selective photocatalysts for the visible light-catalytic reduction of CO2 into CH4.

Photocatalytic conversion of carbon dioxide to methanol over different precursors of graphitic carbon nitride supported on fibrous silica iron

In this study, the graphitic carbon nitride (g-C3N4) was successfully synthesized through thermal polymerization under three different g-C3N4 precursors such as urea (U-gC3N4), melamine (M-gC3N4) and dicyandiamide (D-gC3N4) and then doped into the fibrous silica iron (FSFe), denoted as U-gC3N4/FSFe, MgC3N4/FSFe, and D-gC3N4/FSFe, respectively. The synthesized catalysts were characterized using X-ray Diffraction (XRD), Fourier Transform Infrared Spectrometer (FTIR), and UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis/DRS) and also tested for photocatalytic conversion of carbon dioxide (CO2) to methanol (CH3OH). The study indicated that altering the precursors had a substantial impact on the physicochemical features of the FSFe, which in turn increased the catalytic performance of the conversion of CO2 to CH3OH. U-gC3N4/FSFe exhibits the highest CH3OH yield (2.3 x 104 µmol gcat−1) compared to bare FSFe, D-gC3N4/FSFe and M-gC3N4/FSFe under visible light irradiation within 240 min. The higher CH3OH yield over U-gC3N4/FSFe is mostly owing to the lower bandgap energy of U-gC3N4/FSFe, as well as the advantageous interaction between g-C3N4 and FSFe.

UiO-67 MOF-Based Catalyst as A Potential Photocatalyst for Co2 Conversion to Methanol Complimented by RSM Studies

Metal-organic frameworks (MOFs) have received significant attention in recent years due to their fascinating properties, such as high surface area, porosity, tuneable pore size, and structural flexibility. These characteristics make them promising candidates for various applications, particularly in the photocatalytic conversion of carbon dioxide (CO2). This research investigated the unitisation of Polyoxometalates (POMs) incorporated within MOFs as catalysts for converting CO2 to methanol. The POM@MOF catalyst was prepared by the solvothermal method, and its physicochemical properties were characterised through various techniques, including FTIR, UV-VIS, PXRD, TGA, FESEM, and BET. Response Surface Methodology (RSM) based on Central Composite Design (CCD) was employed to optimise the reaction conditions, focusing on catalyst loading and reaction time. Methanol concentration in the product was determined using HPLC. Notably, the encapsulation of Keggin SW12 into UiO-67(Zr) resulted in better physicochemical properties than pristine UiO-67. The optimal reaction conditions were determined to be a catalyst loading of 1.0 g/L and a reaction time of 3 hours. While the photocatalytic CO2 conversion was successfully conducted, methanol was not detected in both the proposed and modified experimental setups due to the low methanol concentration and the limitations of the detection instruments. This research establishes a lower-limit benchmark and contributes to the development of sustainable processes for CO2 photocatalytic conversion to methanol utilising the SW12@UiO-67 catalyst.Keywords: CO2 conversion, Photocatalyst, RSM, UiO-67, POM@MOF

Photocatalytic Conversion of Carbon Dioxide and Nitrogen Dioxide: Current Developments, Challenges, and Perspectives

Photocatalytic Conversion of Carbon Dioxide and Nitrogen Dioxide: Current Developments, Challenges, and Perspectives

Internal Electric Field and Adsorption Effect Synergistically Boost Carbon Dioxide Conversion on Cadmium Sulfide@Covalent Triazine Frameworks Core–Shell Photocatalyst

AbstractSolar‐driven photocatalytic conversion of carbon dioxide (CO2) into carbon‐neutral fuels is of significance for energy sustainability. The critical challenges in this process are high charge carrier recombination and low CO2 adsorption capacity. Here, by integrating porous covalent triazine frameworks (CTFs) with cadmium sulfide (CdS) nanospheres, a CdS@CTF‐HUST‐1 heterojunction photocatalyst with core–shell structure is developed for CO2‐to‐CO conversion. Experimental investigations combined with density functional theory simulations reveal that the formation of an internal electric field provides the driving force for accelerating S‐scheme charge transfer, resulting in enhanced separation and utilization efficiency of charge carriers in photocatalysis. Together with the improved CO2 adsorption capacity contributed by the porous structure of the CTF‐HUST‐1 shell, the CdS@CTF‐HUST‐1 heterojunction photocatalyst gives an impressive CO yield rate of 168.77 µmol g−1 h−1 with high selectivity. This research furnishes a feasible strategy to construct highly active core–shell composite photocatalysts for optimizing CO2 adsorption and conversion.

Sn and dual-oxygen-vacancy in the Z-scheme Bi2Sn2O7/Sn/NiAl-layered double hydroxide heterojunction synergistically enhanced photocatalytic activity toward carbon dioxide reduction

Photocatalytic conversion of carbon dioxide (CO2) into high value-added chemicals is an attractive yet challenging process, primarily due to the readily recombination of hole-electron pairs in photocatalysts. Herein, dual-oxygen-vacancy mediated Z-scheme Bi2Sn2O7/Sn/NiAl-layered double hydroxide (VO,O-20BSL) heterojunctions were hydrothermally synthesized and subsequently modified with Sn monomers to enhance photocatalytic activity toward CO2 reduction. The abundance of oxygen vacancies endowed the VO,O-20BSL with extended optical adsorption, enhanced charges separation, and superior CO2 adsorption and activation. The interfacial charges transfer of the VO,O-20BSL was demonstrated to follow a Z-scheme mechanism via photochemical deposition of metal/metal oxide. Under visible light irradiation, the VO,O-20BSL exhibited the highest yields of carbon monoxide (CO) and methane (CH4), with values of 72.03 and 0.85 umol·g−1·h−1, respectively, which were 2.66 and 1.57 times higher than that of the VO-NiAl-layered double hydroxide (VO-1LDH). In situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) revealed that carboxylic acid groups (COOH*) and aldehyde groups (CHO*) were the predominant intermediates during CO2 reduction, and accordingly, possible CO2 reduction pathways and mechanism were proposed. This study presents a feasible approach to incorporate dual vacancies into Z-scheme heterojunctions for CO2 reduction.

Armchair Janus WSSe Nanotube Designed with Selenium Vacancy as a Promising Photocatalyst for CO2 Reduction.

Photocatalytic conversion of carbon dioxide into chemical fuels offers a promising way to not only settle growing environmental problems but also provide a renewable energy source. In this study, through first-principles calculation, we found that the Se vacancy introduction can lead to the transition of physical-to-chemical CO2 adsorption on Janus WSSe nanotube. Se vacancies work at the adsorption site, which significantly improves the amount of transferred electrons at the interface, resulting in the enhanced electron orbital hybridization between adsorbents and substrates, and promising the high activity and selectivity for carbon dioxide reduction reaction (CO2RR). Under the condition of illumination, due to the adequate driving forces of photoexcited holes and electrons, oxygen generation reaction (OER) and CO2RR can occur spontaneously on the S and Se sides of the defective WSSe nanotube, respectively. The CO2 could be reduced into CH4, meanwhile, the O2 is produced by the water oxidation, which also provides the hydrogen and electron source for the CO2RR. Our finding reveals a candidate photocatalyst for obtaining efficient photocatalytic CO2 conversion.

Low-cost photoreactors for highly photon/energy-efficient solar-driven synthesis

Low-cost photoreactors for highly photon/energy-efficient solar-driven synthesis

Gallium Oxide Assisting Ag-Loaded Calcium Titanate Photocatalyst for Carbon Dioxide Reduction with Water

An efficient and highly selective photocatalytic conversion of carbon dioxide (CO2) into valuable chemicals such as carbon monoxide (CO) using water (H2O) as an electron donor has been much attractive and deeply desired, which requires the development of advanced photocatalysts based on a functional design. As the Ag-loaded calcium titanate (CaTiO3, CTO) photocatalyst showed a high selectivity to CO2 reduction in aqueous solution and the Ag-loaded gallium oxide (Ga2O3) photocatalyst showed a higher activity for both H2O splitting and CO2 reduction, herein, a series of composite photocatalyst samples consisting of Ga2O3 and CTO were simply fabricated by calcination of the physical mixtures, followed by loading of a Ag cocatalyst with a photodeposition method. The optimized sample with the Ag cocatalyst exhibited both a high CO formation rate of 56.9 μmol h–1 (higher than that of Ag/Ga2O3) and a high selectivity of 95.0% (comparable to Ag/CTO) in the photocatalytic CO2 reduction with H2O. In this composite photocatalyst, most of the electrons generated in the photoexcited Ga2O3 part migrated to the minor CTO particles to contribute to the selective CO2 reduction reaction, which was evidenced by the selective photodeposition of Ag species on the CTO part. The selective CO formation originates from the property of Ag-loaded CTO photocatalyst as the active part in the composite photocatalyst. The Ga2O3 part functions as an antenna to receive the light and donate the photoexcited electrons to the much decorated Ag/CTO part, where the concentrated electrons would promote CO2 reduction with high efficiency.

Enhanced and recyclable CO2 photoreduction into methanol over S-scheme PdO/GdFeO3 heterojunction photocatalyst under visible light

Photocatalytic conversion of carbon dioxide (CO2) into value-added chemicals over ceramic photocatalysts has presently regarded as an eco-friendly and workable approach for saving energy resources and reducing global warming. Accordingly, marvellous research is being performed for engineering enhanced photocatalysts. So, we present a solution-based process for the synthesis of gadolinium orthoferrite nanocrystals (GdFeO3) that are supported with trace amounts (0.5 ∼ 2.0 wt%) of palladium oxide (PdO) to form PdO/GdFeO3 nanocomposites. These synthesized nanostructures were applied for the photocatalytic conversion of carbon dioxide (CO2) into methanol (CH3OH) for the first time. Physicochemical characteristics of the synthesized materials revealed the growth of perovskite GdFeO3nanocrystals supported with tiny PdO dots. Also, a slight reduction in surface areas from 214 to 193 m2g−1 owing to the PdO inclusion. Interestingly, the visible-light absorption was greatly enhanced with a reduction of the overall bandgap down to 2.14 eV compared to 2.37 eV for the pristine GeFeO3. The photoinduced carrier recombination was also suppressed with enhanced mobility, as confirmed by photoluminescence and photocurrent studies. The tuned 2.0 gL−1 dosage of 1.5% PdO/GdFeO3 has resulted in 1550 μmol g−1 CH3OH production within 9 h of visible light illumination, which is > 7.8 times than pristine GdFeO3. Moreover, this novel nanocomposite displays sustainable recyclability of 98% after five cycles. The photocatalytic performance promotion of the 1.5% PdO/GdFeO3 is attributed to the formed heterojunction that enhanced both charge transfer and mobility as well. This work proposes the realization of stable perovskite-based nanoceramics for the production of renewable fuels.

The Photocatalytic Conversion of Carbon Dioxide to Fuels Using Titanium Dioxide Nanosheets/Graphene Oxide Heterostructure as Photocatalyst

Carbon dioxide (CO2) photoreduction to high-value products is a technique for dealing with CO2 emissions. The method involves the molecular transformation of CO2 to hydrocarbon and alcohol-type chemicals, such as methane and methanol, relying on a photocatalyst, such as titanium dioxide (TiO2). In this research, TiO2 nanosheets (TNS) were synthesized using a hydrothermal technique in the presence of a hydrofluoric acid (HF) soft template. The nanosheets were further composited with graphene oxide and doped with copper oxide in the hydrothermal process to create the copper-TiO2 nanosheets/graphene oxide (CTNSG). The CTNSG exhibited outstanding photoactivity in converting CO2 gas to methane and acetone. The production rate for methane and acetone was 12.09 and 0.75 µmol h-1 gcat-1 at 100% relative humidity, providing a total carbon consumption of 71.70 µmol gcat-1. The photoactivity of CTNSG was attributed to the heterostructure interior of the two two-dimensional nanostructures, the copper-TiO2 nanosheets and graphene oxide. The nanosheets-graphene oxide interfaces served as the n-p heterojunctions in holding active radicals for subsequent reactions. The heterostructure also directed the charge transfer, which promoted electron-hole separation in the photocatalyst.

Photocatalytic conversion of carbon dioxide on triethanolamine: Unheeded catalytic performance of sacrificial agent

Potential catalytic performance of sacrificial agents triethanolamine (TEOA) has not been explored yet, seriously affecting the evaluation of catalyst performance and reaction mechanism. Herein, we report direct evidence of TEOA, a popular sacrificial agent in CO2 photoreduction, photocatalytic conversion of CO2 into CO and CH4 for the first time. Combining experimental and theoretical studies, it is corroborated that TEOA with terminal hydroxyl group as active site serves as a photocatalyst possessing appropriate energy level for the ultraviolet light response. Comprehensive investigations endorsed that the two products of CH4 and CO are derived from conventional photocatalytic CO2 hydrogenation and photoinduced homocleavage of RO-COOH followed by a hydrogen atom transfer process, respectively. The current work demonstrates the nonnegligible catalytic influence of TEOA and provides guidance in choosing suitable sacrificial agents during solid–liquid photocatalytic redox reactions.

Cu-doped mesoporous SnO2 nanoparticles with rich grain boundaries and oxygen vacancies for photocatalytic CO2-to-CO conversion.

Photocatalytic conversion of carbon dioxide into fuels provides an effective approach to realize carbon resource utilization. However, the photocatalytic efficiency is still relatively low due to the recombination of photogenerated charges. Herein, we have designed Cu-doped SnO2 nanoparticles (Cu-SnO2) using a glucose-involved hydrothermal crystallization method for the photocatalytic reduction of CO2. The rich oxygen vacancies facilitated the separation and transfer of photogenerated charges, and the confined effect of the typical mesoporous structure promoted the adsorption of CO2, especially a high density of grain boundaries (GBs) and the doping of atomic Cu would introduce new active sites to activate CO2 molecules. This elaborately designed catalyst exhibited super and stable photocatalytic conversion activity of CO2-into-CO, with a CO optimal yield of 107 µmol g-1 in 4 h, which was 2.75 times that over pure SnO2. In situ Raman results indicated that the CO2 reduction reaction followed a *COOH pathway on Cu-SnO2. This work provides implications for the construction of a catalyst with rich defects in the field of energy and environmental catalysis.

Photocatalytic conversion of carbon dioxide, methane, and air for green fuels synthesis

Green fuels are derived from renewable resources that can replace or reduce the use of fossil fuels, and they can help reduce carbon emissions and dependence on finite resources including oil and natural gas.

Understanding inclusive quantum dots hollow CN@CIZS heterojunction for enhanced photocatalytic CO2 reduction

Photocatalytic conversion of carbon dioxide (CO2) to fuel or useful chemicals is of great significance for energy and environmental issues. Herein, we successfully prepare a hollow g-C3N4@Cu-In-Zn-S quantum dots (CN@CIZS QDs) photocatalytic heterojunction employing the method of electrostatic self-assembly. The hollow structure, multiple exciton effect of quantum dots and the discrepancy of band structure generate excellent photocatalytic performance. The yield of CO2 photocatalytic reduction to CO and CH4 respectively is 23.04 μmol g−1 and 13.92 μmol g−1 after simulated visible light irradiation for 6 h for hollow CN@CIZS QDs 20 wt% sample. Moreover, the results of in-situ characterization and other photochemical tests strongly demonstrate the significant optimization of the photocatalytic performance. The research offers a feasible green thought for the resource utilization of CO2.

Advances and challenges in developing cocatalysts for photocatalytic conversion of carbon dioxide to fuels

The global adoption of efficient sustainable energy sources is a crucial step toward meeting energy demands while achieving carbon emission reduction targets. Solar energy has become a clean and cost-competitive alternative to traditional fossil fuels, but the intermittent nature of sunlight results in challenges associated with energy storage and transport. Photocatalytic carbon dioxide reduction intends to mimic natural photosynthesis for utilizing sunlight to chemically convert water and CO2 into fuels. In this process, the solar energy is captured and stored in fuels, so-called solar fuels, for widespread on-demand use. Heterogeneous solar fuel production systems are multi-component, comprising light-harvesting (photosensitizer) and catalytic (cocatalyst) units. Cocatalysts are indispensable for photocatalytic CO2 reduction systems, which promote charge carrier separation and transport, reduce the reaction activation energy, and alter the reaction route, thereby enhancing the activity and selectivity of the photocatalytic reactions. This review presents a comprehensive summary of the recent advancements in cocatalysts for photocatalytic CO2 reduction reaction (CO2RR), with the purpose of providing new insights and guidance to the field with regard to research directions and best practices. We summarize how various cocatalysts including inorganic nanoparticles, metal complexes, enzymes, and bacteria can be combined with semiconductor photosensitizer for light-driven photocatalytic CO2RR. Side-by-side comparisons reveal the strengths and limitations of each kind of cocatalysts and how lessons extracted from studying natural photosynthetic systems can be applied to investigations of artificial photosynthesis, presenting an outlook discussing possible future concepts for a more effective photocatalytic CO2 reduction process.

Photocatalytic Carbon Dioxide Conversion by Structurally and Materially Modified Titanium Dioxide Nanostructures.

TiO2 has aroused considerable attentions as a promising photocatalytic material for decades due to its superior material properties in several fields such as energy and environment. However, the main dilemmas are its wide bandgap (3–3.2 eV), that restricts the light absorption in limited light wavelength region, and the comparatively high charge carrier recombination rate of TiO2, is a hurdle for efficient photocatalytic CO2 conversion. To tackle these problems, lots of researches have been implemented relating to structural and material modification to improve their material, optical, and electrical properties for more efficient photocatalytic CO2 conversion. Recent studies illustrate that crystal facet engineering could broaden the performance of the photocatalysts. As same as for nanostructures which have advantages such as improved light absorption, high surface area, directional charge transport, and efficient charge separation. Moreover, strategies such as doping, junction formation, and hydrogenation have resulted in a promoted photocatalytic performance. Such strategies can markedly change the electronic structure that lies behind the enhancement of the solar spectrum harnessing. In this review, we summarize the works that have been carried out for the enhancement of photocatalytic CO2 conversion by material and structural modification of TiO2 and TiO2-based photocatalytic system. Moreover, we discuss several strategies for synthesis and design of TiO2 photocatalysts for efficient CO2 conversion by nanostructure, structure design of photocatalysts, and material modification.

Ab Initio Electronic Structure Study of the Photoinduced Reduction of Carbon Dioxide with the Heptazinyl Radical.

The photocatalytic conversion of carbon dioxide to liquid fuels with electrons taken from water with solar photons is one of the grand goals of renewable energy research. Polymeric carbon nitrides recently emerged as metal-free materials with promising functionalities for hydrogen evolution from water as well as the activation of carbon dioxide. Molecular heptazine (Hz), the building block of polymeric carbon nitrides, is one the strongest known organic photo-oxidants and has been shown to be able to photo-oxidize water with near-visible light, resulting in reduced (hydrogenated) heptazine (HzH) and OH radicals. In the present work, we explored with ab initio computational methods whether the HzH chromophore is able to reduce carbon dioxide to the hydroxy-formyl (HOCO) radical in hydrogen-bonded HzH-CO2 complexes by the absorption of a photon. In remarkable contrast to the high barrier for carbon dioxide activation in the electronic ground state, the excited-state proton-coupled electron transfer (PCET) reaction is nearly barrierless, but requires the diabatic passage of three conical intersections. The possibility of barrierless carbon dioxide activation by excited-state PCET has so far not been taken into consideration in the interpretation of photocatalytic carbon dioxide reduction on carbon nitride materials.