Photocatalytic Carbon Dioxide Research Articles

Advancing the ethanol pathway during the competitive photocatalytic CO2 reduction in a defective transition metal dichalcogenide

The photocatalytic carbon dioxide (CO2) reduction is a very promising approach for harvesting solar energy and recycling carbon resources. However, the native defects induced competition among different pathways for photocarriers is inevitable and negatively affects the selectivity. This work studies the competition between the vacancy induced pathway and the normal in a molybdenum sulfide selenide during photocatalytic CO2 reduction. It has been revealed that the high concentration of chalcogen vacancies can open up the carbene pathway by lowering the free energy and adjusting the adsorptions for the critical intermediates of *CH2 to attract the neighboring *CO for the C-C coupling in the ethanol production, and therefore improve the ethanol production obviously. We propose that in the design of photocatalysts for C2+ production, construction of variant active sites for the coupling of matching intermediates should be fully considered when choosing the basic materials, dopants and native defects.

Recent Advances in Graphene-Based Single-Atom Photocatalysts for CO2 Reduction and H2 Production

The extensive use of single-atom catalysts (SACs) has appeared as a significant area of investigation in contemporary study. The single-atom catalyst, characterized by its maximum atomic proficiency and great discernment of the transition-metal center, has a unique combination of benefits from both heterogeneous and homogeneous catalysts. Consequently, it effectively bridges the gap between these two types of catalysts, leveraging their distinctive features. The utilization of SACs immobilized on graphene substrates has garnered considerable interest, primarily because of their capacity to facilitate selective and efficient photocatalytic processes. This review aims to comprehensively summarize the progress and potential uses of SACs made from graphene in photocatalytic carbon dioxide (CO2) reduction and hydrogen (H2) generation. The focus is on their contribution to converting solar energy into chemical energy. The present study represents the various preparation methods and characterization approaches of graphene-based single-atom photocatalyst This review investigates the detailed mechanisms underlying these photocatalytic processes and discusses recent studies that have demonstrated remarkable H2 production rates through various graphene-based single-atom photocatalysts. Additionally, the pivotal roleof theoretical simulations, likedensity functional theory (DFT), to understand the structural functional relationships of these SACs are discussed. The potential of graphene-based SACs to revolutionize solar-to-chemical energy conversion through photocatalytic CO2 reduction and H2 production is underscored, along with addressing challenges and outlining future directions for this developing area of study. By shedding light on the progress and potential of these catalysts, this review contributes to the collective pursuit of sustainable and efficient energy conversion strategies to mitigate the global climate crisis.

Construction of a Novel Ternary GQDs/g-C3N4/ZIF-67 Photocatalyst for Enhanced Photocatalytic Carbon Dioxide Reduction

In this study, graphene quantum dots (GQDs) have been incorporated into the g-C3N4/ZIF-67 heterojunction system as a photosensitizer to enhance photocatalytic conversion of CO2-to-CO. The GQDs are deposited onto the surface of g-C3N4/ZIF-67 using a simple water bath procedure. As expected, GQDs/g-C3N4/ZIF-67 presents outstanding performance in CO2 photoreduction. Among the GQDs/g-C3N4/ZIF-67 ternary photocatalysts, 7 GQDs-CN/ZIF-67 exhibits the best photocatalytic CO2 reduction ability with a CO yield of 51.71 μmol g−1, which is 5.05 and 1.87 times more than pristine g-C3N4 (10.24 μmol g−1) and g-C3N4/ZIF-67 (27.65 μmol g−1), respectively. This result shows that upon combination of GQDs with ZIF-67/g-C3N4, GQDs can be used as photosensitizers to improve the optical absorption capacity of the photocatalyst. Furthermore, GQDs serve as electron channels, facilitating the transport of photo-induced electrons from ZIF-67 to g-C3N4, which promotes photogenerated carrier separation efficiency. This study innovatively adds GQDs to the heterojunction and applies the prepared ternary composite to the CO2 photoreduction, which inspires a novel direction for the design of non-noble metal photocatalysts.

Hybrid photocatalyst constructed using polymerized metal complexes and semiconductor powders for photocatalytic carbon dioxide reduction

Abstract Hybrid photocatalysts prepared by the adsorption of metal complexes on semiconductors via anchoring groups are among notable photocatalysts for selective CO2 reduction using abundant electron donors. However, their photocatalytic activities are limited by their low adsorption amounts and strength. In this study, we demonstrate the reductive polymerization of vinyl groups in metal complexes triggered by excited electrons on semiconductors as a new immobilization method. This approach significantly enhanced the adsorption amount and durability, thus increasing the photocatalytic performance.

Engineering Photothermal Catalytic CO2 Nanoreactor for Osteomyelitis Treatment by In Situ CO Generation.

Photocatalytic carbon dioxide (CO2) reduction is an effective method for in vivo carbon monoxide (CO) generation for antibacterial use. However, the available strategies mainly focus on utilizing visible-light-responsive photocatalysts to achieve CO generation. The limited penetration capability of visible light hinders CO generation in deep-seated tissues. Herein, a photothermal CO2 catalyst (abbreviated as NNBCs) to achieve an efficient hyperthermic effect and in situ CO generation is rationally developed, to simultaneously suppress bacterial proliferation and relieve inflammatory responses. The NNBCs are modified with a special polyethylene glycol and further embellished by bicarbonate (BC) decoration via ferric ion-mediated coordination. Upon exposure to 1064nm laser irradiation, the NNBCs facilitated efficient photothermal conversion and in situ CO generation through photothermal CO2 catalysis. Specifically, the photothermal effect accelerated the decomposition of BC to produce CO2 for photothermal catalytic CO production. Benefiting from the hyperthermic effect and in situ CO production, in vivo assessments using an osteomyelitis model confirmed that NNBCs can simultaneously inhibit bacterial proliferation and attenuate the photothermal effect-associated pro-inflammatory response. This study represents the first attempt to develop high-performance photothermal CO2 nanocatalysts to achieve in situ CO generation for the concurrent inhibition of bacterial growth and attenuation of inflammatory responses.

Constructing cuprous oxide-modified zinc tetraphenylporphyrin ultrathin nanosheets heterojunction for enhanced photocatalytic carbon dioxide reduction to methane

The application of supermolecular naonostructures in the photocatalytic carbon dioxide reduction reaction (CO2RR) has attracted increasing attentions. However, it still faces significant challenges, such as low selectivity for multi-electron products and poor stability. Here, the cuprous oxide (Cu2O)-modified zinc tetraphenylporphyrin ultrathin nanosheets (ZnTPP NSs) are successfully constructed through the aqueous chemical reaction. Comprehensive characterizations confirm the formation of type-II heterojunction between Cu2O and ZnTPP in Cu2O@ZnTPP, and the electron transfer from Cu2O to ZnTPP through the Zn-O-Cu bond under the static contact. Under the visible-light irradiation (λ > 420 nm), the optimized Cu2O@ZnTPP sample as catalyst for photocatalytic CO2RR exhibits the methane (CH4) evolution rate of 120.9 μmol/g/h, which is ∼ 4 and ∼ 10 times those of individual ZnTPP NSs (28.0 μmol/g/h) and Cu2O (12.8 μmol/g/h), respectively. Meanwhile, the CH4 selectivity of ∼ 98.7 % and excellent stability can be achieved. Further experiments reveal that Cu2O@ZnTPP has higher photocatalytic conversion efficiency than Cu2O and ZnTPP NSs, and the photoinduced electron transfer from ZnTPP to Cu2O can be identified via the path of ZnTPP→ (ZnTPP•ZnTPP)*→ ZnTPP-→ Zn-O-Cu → Cu2O. Consequently, Cu2O@ZnTPP exhibits a shorter electron-hole separation lifetime (3.3 vs. 9.3 ps) and a longer recombination lifetime (23.1 vs. 13.4 ps) than individual ZnTPP NSs. This work provides a strategy to construct the organic nanostructures for photocatalytic CO2RR to multi-electron products.

Spiral-template from waste tea-leaf to design hierarchical dispersed zinc oxide nanocatalyst for boosting their photocatalytic carbon dioxide reduction

The utilization of cellulose-based templates to enhance the dispersion of zinc oxide (ZnO) nanoparticles represents an effective approach for enhancing their photocatalytic carbon dioxide (CO2) reduction activity. However, the limited availability of surface active sites on linear cellulose fiber has posed a significant challenge for loading ZnO nanoparticles. The present study introduces a technique for segregating spiral vessel (SV) from waste tea-leaves and employing them as templates for in-situ self-assembled ZnO nanoparticles. Due to the inherent three-dimensional (3D) stability of the spiral structure, ZnO nanoparticles exhibit excellent dispersion and maintain a stable hierarchical spiral morphology even after template removal. With the help of a field emission scanning electron microscope (FE-SEM), it could be observed that SV-loaded ZnO nanospheres extracted from waste Pu 'er tea-leaves retained the best spiral morphology after removing the template. The photocatalytic CO2 conversion over spheroidal ZnO with SV as templates (ZnOSS) significantly enhanced yields of CO and CH4, reaching 6.700 and 1.666 μmol·g−1h−1, respectively, surpassing those of other synthesized catalysts. The results obtained from the free radical scavenging experiment and electron paramagnetic resonance (EPR) test demonstrate the pivotal involvement of superoxide radicals (∙O2−) and hydroxyl radicals (∙OH) in the photocatalytic reduction of CO2. Quantum mechanical simulation further verified that the ZnO (0 0 2) crystal face was the best reaction interface with CO2. The design of a cellulose-based spiral template not only facilitates the valorization of waste biomass but also offers a novel perspective for the synthesis of efficient photocatalysts.

Mechanistic exploration in controlling the product selectivity via metals in TiO2 for photocatalytic carbon dioxide reduction

Harnessing the power of the sun, the photocatalytic CO2 reduction process emerges as a pivotal sustainable solution, utilizing solar energy a premier, clean energy source known for its efficiency and economic viability in the current energy paradigm. This study investigates the impact of metals (Cu, Ag, Au) on enhancing the photocatalytic CO2 reduction capabilities of TiO2. In-depth mechanistic analysis conducted using in-situ DRIFTS for identifying the key reaction intermediates, highlights that the catalytic performance, both in terms of activity and product selectivity, is tightly linked to the underlying reaction mechanisms route, optoelectronic properties, and substrate’s (CO2 and H2O) affinities to the catalyst surface. Enhanced light absorption and reduced charge recombination (lifetime enhancement from 0.21 ns to ∼1.2 ns) in case of metal incorporated resulted in enhanced overall photocatalytic performance. With Au as dopant, demonstrated highest electron selectivity for H2 (>97%) compared to Ag and Cu, which showed relatively higher CO2 reduction electron selectivity (∼20% for Cu). The study reveals the crucial interplay of intermediate stabilization, demonstrating its critical role in governing the reaction pathways i.e., carbene or formaldehyde routes as observed in case of Ag and Cu respectively and thus the specific final products. For enhancing the selectivity of CO, engineering the catalyst surface to favour weak CO adsorption is vital. Observations in the CO-TPD measurements demonstrated that Ag sites were effective in promoting the weaker CO* stabilization thus displayed more selectivity towards CO as compared to Cu. While higher CH3OH formation rates in case of Cu, were found to be related to the augmented reactive M=O species stabilization which promotes the oxidation of CH4 to CH3OH. Additionally, in case of Cu, the CH3O* intermediates stabilized effectively, which contributed to more Methanol selectivity through favoured formaldehyde route. While in case of Ag, the CH2* stabilization suggests more probability of the carbene pathway in comparison to the formaldehyde route (as in case of Cu) for producing the CH4 as the final hydrogenated C1 product. These insights guide the strategic design of catalysts for controlling the reaction pathways and thus selective C1 product production in photocatalytic CO2 reduction, offering insights for advanced catalyst design.

BiOCl/BiOBr composites for efficient photocatalytic carbon dioxide reduction

BiOBr (BOB) photocatalysts have low photocatalytic CO2 reduction performance due to their low electron-hole pair separation efficiency. To improve this problem, BiOCl (BOCl) is used as a co-catalyst. BOCl is loaded into BOB to form BiOCl/BiOBr (BOCl/BOB) type Ⅰ heterojunction, which enhances the photocatalytic CO2 reduction performance of BOB by promoting the separation of photogenerated electrons and holes. The results of TPR and PL experiments show that the 20% BOCl/BOB composites have the highest photogenerated carrier separation rate, and the results of CO2 reduction experiments show that 20% BOCl/BOB composites have the best photocatalytic CO2 reduction performance of 7.353 μmolg−1h−1, which is 3.22 and 1.99 times higher than pure BOB and BOCl, respectively. This work provides an effective reference for the development of modified photocatalysts.

Recent Progress on the Surface and Bulk Modification of Carbon Nitrides for Photocatalytic Carbon Dioxide Reduction

Photocatalytic CO2 reduction has been considered as a green and sustainable approach to solve energy and environmental problems. However, the CO2 reduction efficiency of various types of semiconductor photocatalysts studied at this stage is far from realizing practical applications. The challenge of photocatalytic CO2 reduction is to design photocatalysts with excellent catalytic performance. This article summarizes the carbon nitride materials for efficient CO2 reduction and obtaining high value‐added products. The physicochemical properties of carbon nitride materials are discussed in terms of the photocatalytic mechanisms (bandgap tuning, high specific surface area, shorter electron–hole transmission paths, increasing the number of active sites, etc.). The present review provides the latest research progress of carbon nitride modification strategies. The prospects and challenges for the application of carbon nitride materials for CO2 reduction are presented. This review article will provide useful guidance for further research on carbon nitride materials for efficient photocatalytic CO2 reduction.

Titanium carbide sealed cadmium sulfide quantum dots on carbon, oxygen-doped boron nitride for enhanced and durable photochemical carbon dioxide reduction

Despite great efforts that have been made, photocatalytic carbon dioxide (CO2) reduction still faces enormous challenges due to the sluggish kinetics or disadvantageous thermodynamics. Herein, cadmium sulfide quantum dots (CdS QDs) were loaded onto carbon, oxygen-doped boron nitride (BN) and encapsulated by titanium carbide (Ti3C2, MXene) layers to construct a ternary composite. The uniform distribution of CdS QDs and the tight interfacial interaction among the three components could be achieved by adjusting the loading amounts of CdS QDs and MXene. The ternary 100MX/CQ/BN sample gave a productive rate of 2.45 and 0.44 μmol g-1 h−1 for carbon monoxide (CO) and methane (CH4), respectively. This CO yield is 1.93 and 6.13 times higher than that of CdS QDs/BN and BN counterparts. The photocatalytic durability of the ternary composite is significantly improved compared with CdS QDs/BN because MXene can protect CdS from photocorrosion. The characterization results demonstrate that the excellent CO2 adsorption and activation capabilities of BN, the visible light absorption of CdS QDs, the good conductivity of MXene and the well-matched energy band alignment jointly promote the photocatalytic performance of the ternary catalyst.

A quadruple transition metal dichalcogenide for variously synergetic electron behaviors during photocatalytic carbon dioxide reduction

A quadruple 2H transition metal dichalcogenide of platinum doped molybdenum selenide sulfide (MoSSe) has been achieved. The critical doping amount of Pt is estimated to be approximately 0.9 a.t.% to prevent the formation of a heterogeneous phase. It has been observed that the excess Pt beyond this critical doping level cannot be settled into the lattice of MoSSe but forms an independent metal phase of Pt nanoparticles, composing a heterostructure with MoSSe, in which the behavior of photogenerated electrons will be predominantly governed by metal Pt and transported along the pathways for gas production in the photocatalytic CO2 reduction. However, as long as Pt can be located in the lattice of MoSSe, the elemental variety of Pt doped MoSSe has provided various active sites during the photocatalytic CO2 reduction process, favoring the localized coupling of matching intermediates, consequently enhancing the production of high value-added liquid products. In essence, the successful integration of Pt into the 2H MoSSe lattice opens up diverse active sites, optimizing the photocatalytic performance on the selectivity of liquid production reduced from CO2.

Synergistic promotion for the performance of photocatalytic carbon dioxide reduction by vacancy engineering and N-doped carbon nanotubes

The structural devise of photocatalytic materials are closely related to the separation of photogenerated carriers and the transport of charge, which is crucial to enhance the performance of photocatalytic carbon dioxide reduction reaction (CO2RR). Here, a photocatalyst (CdS-SV@Co@NCNT) has been successfully prepared by growing cadmium sulfide nanoparticles with sulfur vacancies on N-doped carbon nanotubes through a simple solvothermal method. The intrinsic electronic structure is regulated by sulfur vacancies to promote photocatalytic activity. Meanwhile, a larger specific surface area of Co@NCNT could expose more reaction sites and shorten the transfer distance of photogenerated carriers. Furthermore, the combination with Co@NCNT could effectively suppress the photocorrosion of CdS. The possible photocatalytic CO2RR path is further speculated by in-situ infrared test results, in which CO2 molecules adsorbed on sulfur vacancies preferentially generate important intermediate COOH*, which is then reduced to CO and CH4. Therefore, it exhibits a high CO yield of 263.3 μmol·g−1·h−1 and trace of CH4 while showing excellent stability. This research provides a novel idea for designing the photocatalysts with highly active and stability for CO2RR.

Nanoflower-like TiO2/CoAl-layered double hydroxide direct Z-scheme for boosted photocatalytic CO2 conversion

Direct Z-scheme heterojunction (DZH) has promising potential in photocatalytic carbon dioxide reduction (PCR) owing to its unusual charge transfer pathway, exceptional charge separation efficiency, and high redox ability. Herein, ultrathin TiO2 nanosheets (NSs) have been employed as a substrate for the in-situ growth of CoAl layered double hydroxide (LDH) NSs to fabricate nanoflower-like TiO2/CoAl-LDH (TCA) DZH. The unconsolidated heterostructure is beneficial for active site exposure and mass transfer, and the inherent alkalinity of CoAl-LDH promoted the adsorption of CO2, synergistically boosting the process of PCR reaction in the TCA system. Simulated calculation and in-situ analysis jointly demonstrate the unique electron transfer processes during hybridization and photoexcitation. The resulting (-)TiO2/(+)CoAl-LDH interfacial electric field and DZH further lead to efficient separation of photogenerated charges of TCA. In the solid–gas system, the optimized TCA heterojunction exhibits a competitive PCR activity (76.18 μmol g−1h−1 for CO production rate) increase of 31.6 and 20.3 times compared to TiO2 and CoAl-LDH, respectively.

Recent progress of MXene as a cocatalyst in photocatalytic carbon dioxide reduction

Due to the excessive consumption of fossil fuel resources and the emission of a substantial quantity of CO2 into the environment, it is urgent to develop clean energy solutions. In order to reduce carbon emissions from the source, it is effective approach to convert CO2 into various renewable energy fuels. Inspired by the photosynthesis of green plant, CO2 is converted into clean fuel with the aid of catalysts. Regarding the separation and transfer of photogenerated charge carriers, and inadequate adsorption and activation of CO2 on the surface of catalysts, the current semiconductors utilized in photocatalysis have low efficiency. As a result, the current efficiency of photocatalysts is far from meeting the need for practical industrial demands. MXene materials, for example Ti3C2Tx (9980 S cm−1), have emerged as a promising candidate for CO2 reduction due to the significant number of active sites for functional groups, high conductivity and low defects, large surface areas, and outstanding visible light photoelectronic properties. This review provides a critical overview of the recent progress regarding MXene as a co-catalyst in photocatalytic CO2 reduction systems. We systemically explore the fundamental principles and reaction mechanisms associated with separating and transferring photogenerated charge carriers. Additionally, we investigate the basic properties of MXene as a co-catalyst in the context of CO2 reduction. Furthermore, this review also elucidates the impacts of the microstructure of photocatalysts on enhancing photocatalytic performance. Finally, the challenges and opportunities in using MXene as a co-catalyst for CO2 reduction have been presented to inspire further research in this field.

Defect and nanostructure engineering of polymeric carbon nitride for visible-light-driven CO2 reduction

Sunlight-induced photocatalytic carbon dioxide (CO2) reduction to energy-rich chemicals by metal-free polymeric carbon nitride (CN) semiconductor is a promising tactic for sustained solar fuel production. However, the reaction efficiency of CO2 photoreduction is restrained seriously by the rapid recombination of photogenerated carriers on CN polymer. Herein, we incorporate 2-aminopyridine molecule with strong electron-withdrawing group into the skeleton edge of CN layers through a facile one-pot thermal polymerization strategy using urea as the precursor, which renders a modified carbon nitride (ACN) with extended optical harvesting, abundant nitrogen defects and ultrathin nanosheet structure. Consequently, the ACN photocatalyst with desirable structural features attains enhanced separation and migration of photoexcited charge carriers. Under visible light irradiation with Co(bpy)32+ as a cocatalyst, the optimized ACN sample manifests a high CO2 deoxygnative reduction activity and high stability, providing a CO yielding rate of 17 μmol h−1, which is significantly higher than that of pristine CN. The key intermediates engaged in CO2 photoreduction reaction are determined by the in situ diffuse reflectance infrared Fourier transform spectroscopy, which sponsors the construction of the possible photocatalytic CO2 reduction mechanism on ACN nanosheets.

Novel lead-free halide perovskite KMgI3 for photocatalytic hydrogen evolution (HER) and carbon dioxide reduction reaction (CO2RR)

Lead-free magnesium iodide (KMgI3) perovskite films were obtained by ink-jet printing. The halide perovskites were printed in different supports: mica, magnesium oxychloride, and glass. The printed samples were evaluated in photocatalytic hydrogen evolution (HER) and carbon dioxide reduction reaction (CO2RR) to produce alternative solar based fuels, e.g., formic acid (HCOOH) and hydrogen (H2) under visible light. The KMgI3 printed on mica exhibited the highest activity to produce both HCOOH and H2, with apparent quantum yields of 1.02 and 7.86 % at 550 nm, respectively. This result was associated with an enhanced adhesion of the perovskite to mica due to the K+ affinity and a better interaction of the C atom possible due to the depletion of the layer of K+, leading to the exposure of aluminosilicate sheets. The stability of the perovskite was corroborated after three consecutive cycles.

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.

Challenges in Photocatalytic Carbon Dioxide Reduction

Challenges in Photocatalytic Carbon Dioxide Reduction

Accelerated Photocatalytic Carbon Dioxide Reduction and Water Oxidation under Spatial Synergy.

Photocatalytic conversion of CO2 and H2 O into fuels and oxygen is a highly promising solution for carbon-neutral recycling. Traditionally, researchers have studied CO2 reduction and H2 O oxidation separately, overlooking potential synergistic interplay between these processes. This study introduces an innovative approach, spatial synergy, which encourages synergistic progress by bringing the two half-reactions into atomic proximity. To facilitate this, we developed a defective ZnIn2 S4 -supported single-atom Cu catalyst (Cu-SA/D-ZIS), which demonstrates remarkable catalytic performance with CO2 reduction rates of 112.5 μmol g-1 h-1 and water oxidation rates of 52.3 μmol g-1 h-1 , exhibiting a six-fold enhancement over D-ZIS. The structural characterization results indicated that the trapping effect of vacancy associates on single-atom copper led to the formation of an unsaturated coordination structure, Cu-S3 , consequently giving rise to the CuZn 'VS ⋅⋅VZn " defect complexes. FT-IR studies coupled with theoretical calculations reveal the spatially synergistic CO2 reduction and water oxidation on CuZn 'VS ⋅⋅VZn ", where the breakage of O-H in water oxidation is synchronized with the formation of *COOH, significantly lowering the energy barrier. Notably, this study introduces and, for the first time, substantiates the spatial synergy effect in CO2 reduction and H2 O oxidation through a combination of experimental and theoretical analyses, providing a fresh insight in optimizing photocatalytic system.