Performance For CO2 Hydrogenation Research Articles

Recent Advances in Alloy Catalysts for CO2 Hydrogenation to Methanol

AbstractThe increasing anthropogenic carbon dioxide emissions (CO2) have a huge environmental impact, and CO2 emission reduction is already a common view in our society. Recently, selective hydrogenation of CO2 to methanol has attracted much attention because the process can effectively mitigate CO2 emissions and simultaneously produce high‐value‐added chemicals and fuels. The catalysts play a very important role in achieving high efficiency of CO2 to methanol. As one promising alternative, the alloy catalysts have demonstrated high performance in CO2 hydrogenation to methanol due to their unique geometry and electronic properties. Herein, we review the recent advances in alloy catalysts, including solid solution alloys and intermetallic compounds (mainly Cu‐based, In‐based, Ga‐based, and other alloy catalysts) for heterogeneous catalysis of CO2 hydrogenation to methanol. Moreover, the research ideas and development prospects of alloy catalysts for CO2 hydrogenation to methanol are overviewed to provide the ideas and references for the subsequent research on alloy catalysts for CO2 hydrogenation.

Study on Catalytic Performance in CO2 Hydrogenation to Methanol over Au–Cu/C3N4 Catalysts

In this paper, Au and Cu nanoparticles were successfully loaded onto porous g-C3N4 material through a hydrothermal synthesis method. By adjusting the proportion of Cu, Au-5%Cu/C3N4, Au-10%Cu/C3N4, and Au-15%Cu/C3N4, catalysts were prepared and used for the catalytic reduction of CO2 to methanol. Characterization analysis using high-resolution XPS spectra showed that with an increase in the doping amount of Cu, the electron cloud density on the Cu surface initially increased and then decreased. Electrons from Au atoms transferred to Cu atoms, leading to the accumulation of a more negative charge on the Cu surface, promoting the adsorption of partially positively charged C in CO2, which is more beneficial for catalyzing CO2. Among them, Au-10%Cu/C3N4 exhibited good reducibility and strong basic sites, as demonstrated by H2-TPR and CO2-TPD, with the conversion rates for CO2, methanol yield, and methanol selectivity being 11.58%, 41.29 g·kg−1·h−1 (0.39 μmol·g−1s−1), and 59.77%, respectively.

Tuning the CO2 hydrogenation activity and selectivity of TiO2 nanorods supported Rh catalyst via secondary‐metals addition

AbstractSecondary‐metals promotion is key to tune the CO2 hydrogenation performance of Rh‐based catalyst. We describe the addition of Cu or Co in TiO2 nanorods supported Rh catalyst (viz., RhMx/TiO2), showing significant impact on the CO2 hydrogenation activity and productivity. Cu addition can promote the partial hydrogenation to alcohols (methanol and ethanol), whereas Co led to the deep hydrogenation to alkanes (CH4, C2H6). Comparative time‐resolved in situ DRIFTS studies with H2/D2 isotopic exchange further reveal that both surface adsorbed CO* and formates could be the key reaction intermediates during the CO2 hydrogenation over RhMx/TiO2 (especially the RhCu2.5/TiO2), in which the interaction strength of CO* regulated by secondary‐metals addition was key to tune the reaction pathways and productivity. The findings suggested that rational design of active metal sites, for example the synergy between Rh and secondary‐metals, is highly needed to promote the CO insertion and CC coupling to produce ethanol.

Synergistic effect of Fe-Mn bimetallic sites with close proximity for enhanced CO2 hydrogenation performance

Synergistic effect of Fe-Mn bimetallic sites with close proximity for enhanced CO2 hydrogenation performance

Theoretical study of the effects of surface Cu coordination environment on CO2 hydrogenation to CH3OH

The coordination environment of Cu (the coordination number and arrangement of surface atoms) plays an important role in CO2 hydrogenation to CH3OH. Compared with the extensive studies of the effects of coordination number, the comprehensive effects of coordination number and arrangement of surface atoms were seldom explored in literature. To unravel the effects of surface Cu coordination environment on CO2 hydrogenation to CH3OH, the adsorption and reaction behaviors of H2 and CO2 on Cu(111), (100), (110) and (211) with different coordination numbers and arrangement of surface Cu were systematically calculated by density functional theory (DFT) and kinetic Monte Carlo (kMC) simulation. It was found that the adsorption energies of intermediates in CO2 hydrogenation on Cu surfaces increase with the decrease of coordination number. When the Cu coordination numbers are similar, the charge density on the open surface derived from the different atom arrangement becomes larger and leads to stronger interaction with intermediates than that on the compact one. DFT calculation and kMC simulation indicate that methanol formation pathway follows CO2*→HCOO*→HCOOH*→H2COOH*→H2CO*→CH3O*→CH3OH* on four Cu facets; CO formation is via CO2 direct dissociation on Cu(111), (100) and (110) but COOH* dissociation on (211). The low-coordinated surface Cu with more openness on Cu(211) is the highly active site for CO2 hydrogenation to CH3OH with high turnover of frequency (3.71 × 10−4 s−1) and high selectivity (87.17 %) at 600 K, PCO2 = 7.5 atm and PH2 = 22.5 atm, which is much higher than those on Cu(111), (100) and (110). This work unravels the effects of coordination environment on CO2 hydrogenation at the molecular level and provides an important insight into the design and development of catalysts with high performance in CO2 hydrogenation to CH3OH.

Sodium-assisted MoS2 for boosting CO2 hydrogenation to methanol: The crucial role of sodium in defect evolution and modification

The effective conversion of CO2 to methanol utilizing green hydrogen under moderate conditions represents a promising approach for achieving carbon neutrality. MoS2 demonstrates exceptional catalytic performance at temperatures below 200 °C, however, generating in-plane sulfur defects is challenging due to the intact planar structure. Introducing heteroatoms to induce sulfur vacancy formation and modulate their chemical environment remains a significant obstacle. In this study, we developed a NaCl-assisted method for synthesizing MoS2 and discovered that a small quantity of sodium not only promotes the formation of sulfur vacancies during the induction period, but also encourages CO2 hydrogenation via the carboxylate route, as opposed to the CO2 dissociation to CO* route over non-modified sulfur vacancies. Furthermore, catalysts at various stages throughout the 60 h induction period were characterized, revealing that the increase in sulfur vacancies and enhanced H2 dissociation capability are primary factors contributing to improved methanol yield. The sodium-modified MoS2 achieves a methanol space–time yield of up to 571 mgMeOH gcat.−1 h−1 at 200 °C and 5 MPa with a 4.8% CO2 conversion and 96% methanol selectivity. The turnover frequency based on total sulfur vacancies reaches 170 h−1. This research is anticipated to offer a new strategy for enhancing the catalytic performance of CO2 hydrogenation to methanol using heteroatom-assisted defect engineering.

Exploring the Effect of the Solvothermal Time on the Structural Properties and Catalytic Activity of Cu-ZnO-ZrO2 Catalysts Synthesized by the Solvothermal Method for CO2 Hydrogenation to Methanol

A series of Cu-ZnO-ZrO2 (CCZ) catalysts were prepared by the solvothermal method with different solvothermal times (1 h, 3 h, 6 h, and 12 h). The physicochemical properties of these catalysts and the catalytic performance for CO2 hydrogenation to methanol were studied. The highest methanol yield was achieved when the solvothermal time was 6 h (CCZ-6). Furthermore, we found that the copper surface area (SCu) increases and then decreases with an increase in the solvothermal time and that there is a strong correlation between the methanol yield and the SCu. This research highlights the crucial influence of the solvothermal time on the structure and catalytic behavior of Cu-ZnO-ZrO2 catalysts, providing a valuable reference for the development of efficient catalysts.

Sustainable approach for CO2 hydrogenation to formic acid with Ru single atom catalysts on nitrogen-doped carbon prepared from green algae

Ruthenium catalysts supported on nitrogen-doped carbon (NDC) have gained attention due to their exceptional catalytic performance for CO2 hydrogenation to formic acid, a key solution to mitigate CO2 emissions. However, conventional methods for preparing NDC typically rely on petrochemical compounds, which are not environmentally friendly. Herein, we propose a sustainable and innovative approach by employing protein-rich green algae as a source to prepare NDC for Ru catalysts. To maximize the CO2 reduction effect, flue gas exhausted from industrial processes was utilized as a CO2 feed to cultivate the green algae in a photobioreactor. The harvested green algae were pyrolyzed at 800 °C under an N2 atmosphere to prepare the NDC. After the metalation of Ru on prepared NDC, the Ru catalysts exhibited a turnover number of 7,599 for CO2 hydrogenation which demonstrated the potential of green algae as a raw material for NDC. However, the catalysts were deactivated due to the leaching or agglomeration of weakly bound Ru analyzed by experimental and theoretical investigations. We applied a NaBH4 treatment to stabilize the Ru active sites, and the treated catalysts retained 99.6 % of their initial catalytic activity after five recycling tests. Furthermore, Ru on NDC achieved a cumulative turnover number of 16,000 after 24 h. This study offers a sustainable and eco-friendly method for reducing CO2 emissions, combining the cultivation of green algae with waste flue gas and the production of formic acid via CO2 hydrogenation using improved Ru catalysts on algae-derived NDC.

On the Capabilities of Transition Metal Carbides for Carbon Capture and Utilization Technologies.

The search for cheap and active materials for the capture and activation of CO2 has led to many efforts aimed at developing new catalysts. In this context, earth-abundant transition metal carbides (TMCs) have emerged as promising candidates, garnering increased attention in recent decades due to their exceptional refractory properties and resistance to sintering, coking, and sulfur poisoning. In this work, we assess the use of Group 5 TMCs (VC, NbC, and TaC) as potential materials for carbon capture and sequestration/utilization technologies by combining experimental characterization techniques, first-principles-based multiscale modeling, vibrational analysis, and catalytic experiments. Our findings reveal that the stoichiometric phase of VC exhibits weak interactions with CO2, displaying an inability to adsorb or dissociate it. However, VC often exhibits the presence of surface carbon vacancies, leading to significant activation of CO2 at room temperature and facilitating its catalytic hydrogenation. In contrast, stoichiometric NbC and TaC phases exhibit stronger interactions with CO2, capable of adsorbing and even breaking of CO2 at low temperatures, particularly notable in the case of TaC. Nevertheless, NbC and TaC demonstrate poor catalytic performance for CO2 hydrogenation. This work suggests Group 5 TMCs as potential materials for CO2 abatement, emphasizes the importance of surface vacancies in enhancing catalytic activity and adsorption capability, and provides a reference for using the infrared spectra as a unique identifier to detect oxy-carbide phases or surface C vacancies within Group 5 TMCs.

Flame Spray Pyrolysis Synthesis of Ultra-Small High-Entropy Alloy-Supported Oxide Nanoparticles for CO2 Hydrogenation Catalysts.

The synthesis of high-entropy alloys (HEAs) with ultra-small particle sizes has long been a challenging task. The complex and time-consuming synthesis process hinders their practical application and widespread adoption. This study presents the novel synthesis of TiO2 nanoparticles loaded with a quinary high-entropy alloy through flame spray pyrolysis (FSP) for the first time. The extremely fast heating rate of flame combustion makes the precursor fast pyrolysis gasification, high temperature in the flame field promotes the metal vapor mixing uniformly, and the fast quenching process can reduce the particle aggregation sintering, the ultra-small particle size of HEA firmly attached to the TiO2 surface. The catalysts prepared via this gas-to-particle pathway exhibit excellent performance in CO2 hydrogenation, achieving a conversion rate of 62% at 450°C, and maintaining their activity for over 220h without significant particle agglomeration. This finding provides valuable insights for the future design of catalytically active materials with enhanced activity and long-term stability.

Rich oxygen vacancies in core–shell structured Co3O4-CuO-ZnO@ZIF-8 for boosting CO2 hydrogenation to methanol

Converting carbon dioxide (CO2) into high-quality methanol to alleviate the energy crisis is a promising strategy. However, as a traditional catalyst for CO2 hydrogenation to methanol, Cu/ZnO exhibits low CO2 conversion and low methanol selectivity at low temperature. In order to improve the catalytic performance of CO2 hydrogenation to methanol, Co3O4 was introduced to form Co3O4-CuO-ZnO with flower-like structure, and then diamond-shaped ZIF-8 particles with large specific surface area and rich oxygen vacancies were synthesized on the surface of Co3O4-CuO-ZnO by hydrothermal method. A series of characterizations showed that the synthesis of ZIF-8 greatly increased the specific surface area of the catalyst. The oxygen vacancy is the site of CO2 adsorption and activation, and stabilizes the reaction intermediate, which promotes the conversion of CO2 and the formation of methanol. The introduction of Co promotes the formation of the alloy phase, enhances the interaction between the metals, makes the active center more dispersed, reduces the sintering of the catalyst, and thus exhibits better catalytic performance. Among co-precipitated CuO-ZnO, hydrothermal CuO-ZnO, CuO-ZnO@ZIF-8, Co3O4-CuO-ZnO and Co3O4-CuO-ZnO@ZIF-8 catalysts, Co3O4-CuO-ZnO@ZIF-8 exhibits the best catalytic performance (CO2 conversion 16.06% and CH3OH selectivity 94.58%). Based on the above design, ZIF-8 and Co3O4 synergistic CuO-ZnO catalyst effectively improved CO2 conversion and CH3OH selectivity.

Preparation of palladium-based catalyst by plasma-assisted atomic layer deposition and its applications in CO2 hydrogenation reduction

Supported Pd catalyst is an important noble metal material in recent years due to its high catalytic performance in CO2 hydrogenation. A fluidized-bed plasma assisted atomic layer deposition (FP-ALD) process is reported to fabricate Pd nanoparticle catalyst over γ-Al2O3 or Fe2O3/γ-Al2O3 support, using palladium hexafluoroacetylacetonate as the Pd precursor and H2 plasma as counter-reactant. Scanning transmission electron microscopy exhibits that high-density Pd nanoparticles are uniformly dispersed over Fe2O3/γ-Al2O3 support with an average diameter of 4.4 nm. The deposited Pd-Fe2O3/γ-Al2O3 shows excellent catalytic performance for CO2 hydrogenation in a dielectric barrier discharge reactor. Under a typical condition of H2 to CO2 ratio of 4 in the feed gas, the discharge power of 19.6 W, and gas hourly space velocity of 10000 h−1, the conversion of CO2 is as high as 16.3% with CH3OH and CH4 selectivities of 26.5% and 3.9%, respectively.

In Situ Carbon-Confined MoSe2 Catalyst with Heterojunction for Highly Selective CO2 Hydrogenation to Methanol.

The synthesis of methanol from CO2 hydrogenation is an effective measure to deal with global climate change and an important route for the chemical fixation of CO2. In this work, carbon-confined MoSe2 (MoSe2@C) catalysts were prepared by in situ pyrolysis using glucose as a carbon source. The physico-chemical properties and catalytic performance of CO2 hydrogenation to yield methanol were compared with MoSe2 and MoSe2/C. The results of the structure characterization showed MoSe2 displayed few layers and a small particle size. Owing to the synergistic effect of the Mo2C-MoSe2 heterojunction and in situ carbon doping, MoSe2@C with a suitable C/Mo mole ratio in the precursor showed excellent catalytic performance in the synthesis of methanol from CO2 hydrogenation. Under the optimal catalyst MoSe2@C-55, the selectivity of methanol reached 93.7% at a 9.7% conversion of CO2 under optimized reaction conditions, and its catalytic performance was maintained without deactivation during a continuous reaction of 100 h. In situ diffuse infrared Fourier transform spectroscopy studies suggested that formate and CO were the key intermediates in CO2 hydrogenation to methanol.

The Pd/ZrO2 catalyst inversely loaded with various metal oxides for methanol synthesis from carbon dioxide

The selectivity and stability of catalysts for methanol synthesis from CO2 still remain to be enhanced. In this work, we synthesized a series of Pd/ZrO2 catalysts inversely loaded with various metal oxide promoters (ZnO, In2O3, and CeO2), those would partially cover Pd metal surface and form some new metal-promoter interface, to explore the nature in the performance of CO2 hydrogenation to methanol. The catalyst synthesized by this approach could limit the growth of Pd particles during the reduction and form new metal–metal oxide interfaces with different functions of CO2 hydrogenation, improving the reaction performance of Pd-ZrO2 catalysts. As a result, the ZnO-Pd/ZrO2 catalyst exhibited the highest CO2 conversion (12.0 %), methanol selectivity (95.6 %), and STY of methanol (472 gMeOHkgcat-1h−1), with excellent stability. The results of HRTEM, H2-TPR, XPS, and XAFS showed that the ZnO-Pd/ZrO2 catalyst had the typical Pd-ZnO interface with Pd2+ species after the H2 reduction, which could enhance the adsorption and activation of CO2. In addition, the in situ DRIFTS and NAP-XPS results implied that the Pd-ZnO interface significantly improved the formation of formate (HCOO*) and methoxy (H3CO*) species, which were considered to be the key intermediates of methanol generation, and thus greatly enhanced the selectivity of methanol.

Deciphering the structural evolution and real active ingredients of iron oxides in photocatalytic CO2 hydrogenation

Photocatalytic CO2 hydrogenation reactions can produce high-value-added chemicals for industry, solving the environmental problems caused by excessive CO2 emissions. Iron oxides are commonly used in photocatalytic reactions due to their various structures and suitable band gaps. Nevertheless, the structural evolution and real active components during photocatalytic CO2 hydrogenation reaction are rarely studied. Herein, a variety of iron oxides including α-Fe2O3, γ-Fe2O3, Fe3O4 and FeO were derived from Prussian blue precursors to investigate the CO2 hydrogenation performance, structural evolution and active components. Especially, the typical α- and γ-Fe2O3 are converted to Fe3O4 during the reaction, while Fe/FexOy remains structurally stable. Meanwhile, it is confirmed that Fe3O4 is the main active component for CO production and the formation of hydrocarbons (CH4 and C2–C4) are highly dependent on the Fe/FexOy heterojunctions. The optimal yields of CO, CH4 and C2–C4 hydrocarbons over the best catalyst (FeFe-550) can achieve 4 mmol g−1 h−1, 350 μmol g−1 h−1 and 150 μmol g−1 h−1, respectively due to their suitable metal/oxide component distribution. This work examines the structural evolution of different iron oxide catalysts in the photocatalytic CO2 hydrogenation reaction, identifies the active components as well as reveals the relationship between components and the products, and offers valuable insights into the efficient utilization of CO2.

Exploiting Co-C interface and graphitic carbon belts for enhanced structural stability of a porous layered Co-C catalyst for CO2 hydrogenation

Addressing the urgent need for efficient CO2 reduction, a novel Co@C catalyst was synthesized through the pyrolysis of a unique layered metal–organic framework (MOF), featuring tunable thickness, pore sizes. The CO2 hydrogenation performance demonstrates an enhancement by an optimized structure that significantly improves stability, maintaining a 25% CO2 conversion rate over an extended 80-hour period. The catalyst's composite structure exhibits a dual-confinement effect, where the Co-C interface and graphitic carbon belt stabilize Co nanoparticles, preventing sintering during reaction cycles. This study delves into the structural modifications necessary for catalytic optimization in CO2 hydrogenation, offering valuable insights for designing efficient catalysts for CO2 reduction and advancing sustainable energy solutions.

Highly selective CuO-ZnO@Cu-MOR catalysts prepared by ultrafast solid processing for carbon dioxide hydrogenation to methanol

The conversion of CO2 into methanol has emerged as a promising strategy for addressing climate change and optimizing the utilization of carbon resources. Conventional synthesis methods for Cu-based catalysts, such as co-precipitation, necessitate the consumption of substantial amounts of solvent and meticulous control over preparation conditions, while also being susceptible to deactivation by water during hydrogenation. Therefore, it is crucial to develop a catalyst that can be readily synthesized and exhibits outstanding performance and durability. In this study, we present an ultrafast (only 20 min), solid-phase grinding approach to fabricate CuO-ZnO@Cu-MOR catalysts for CO2 hydrogenation to methanol. The resulting catalysts were comprehensively characterized using XRD, XPS, H2-TPR, NH3-TPD, SEM, HRTEM, and In-situ-FTIR techniques. Notably, the CuO-ZnO@Cu-MOR catalysts with a distinctive capsule-like structure displayed a high catalytic performance for CO2 hydrogenation. The byproducts of methane and water produced by the CO2 hydrogenation process were able to be further converted to methanol through Cu-MOR, leading to a significant enhancement of the methanol selectivity (95.6 %) and CO2 conversion (22.8 %). Moreover, a long-term test lasting 300 h demonstrated constant catalytic performances and superior durability.

Boron-doped Cu-Co catalyst boosting charge transfer in photothermal carbon dioxide hydrogenation

Photothermal catalysis of CO2 hydrogenation holds great potential in achieving carbon neutrality. However, the rational design of cost-effective photothermal catalysts with high performance for CO2 hydrogenation is an ongoing challenge. Herein, we employed CuCoyBOₓ composite catalysts by incorporating both CuBOₓ and amorphous CoBOₓ to efficiently catalyze the CO2 hydrogenation. Besides the high selectivity (98.0%), the optimized CuCo5BOx demonstrated a remarkable CO yield of 124.7 mmol g⁻¹ h⁻¹ under illumination at 300°C, which was 3 times higher than the traditional thermocatalysis. Experimental results and theoretical calculations demonstrated CuBOₓ acted as a photocatalyst, donating electrons to CoBOₓ active sites. Coupling boron-oxygen species with CuCo bimetallic-oxides synergically enhanced the CO2 adsorption capacity and accelerated charge transfer, thereby enhancing the photothermal synergistic effect and consequently boosting the catalytic activity. This study establishes an approach for the rational design of non-precious metal-boride catalysts, enabling efficient photothermal conversion of CO2 into CO under mild conditions.

Review of Mechanism Investigations and Catalyst Developments for CO2 Hydrogenation to Alcohols

Heterogeneous thermal-catalytic CO2 hydrogenation to alcohols using renewable energy is a highly attractive approach for recycling greenhouse gases into high-value chemicals and fuels, thereby reducing the dependence on fossil fuels, while simultaneously mitigating the CO2 emission and environmental problems. Currently, great advances have been made on the heterogeneous catalysts, but an in-depth and more comprehensive understanding to further promote this reaction process is still lacking. Herein, we highlight the thermodynamic and kinetic analysis of CO2 hydrogenation reaction firstly. Then, various reaction pathways for CO2 hydrogenation to methanol and higher alcohols (C2+ alcohols) have been discussed in detail, respectively, by combining the experimental studies and density functional theory calculations. On this basis, the key factors influencing the reaction performance, such as metal dispersion, support modification, promoter addition and their structural optimization, are summarized on the metal-based and metal-oxide-based catalysts. In addition, the catalytic performance of CO2 hydrogenation to alcohols and the relationship between structure and properties are mainly summarized and analyzed in the past five years. To conclude, the current challenges and potential strategies in catalyst design, structural characterization and reaction mechanisms are presented for CO2 hydrogenation to alcohols.

Alkali metal promotion on Fe-Co-Ni trimetallic catalysts for CO2 hydrogenation to light olefins

The catalyst obtained by calcination of the precursor Fe-Co-Ni trimetallic MOFs has exhibited great CO2 hydrogenation performance. To further improve the selectivity of target product light olefins and the catalyst stability, alkali metal doping is used to modify the Fe-Co-Ni trimetallic catalyst, and the effects of different types of alkali metals and different doping methods are also studied. After alkali metal doping, the increased electron concentration around Fe atoms, the enhanced alkalinity of the catalyst surface and the weakened H2 activation can improve CO2 uptake while decreasing H2 affinity, thereby inhibiting the alkane formation. Among all the catalysts doped by alkali metal, FCN-K(a) obtained by potassium citrate impregnation after calcining has the largest specific surface area, the highest microporosity and the most alkaline sites on its surface, showing the best CO2 hydrogenation performance with a CO2 conversion of 47.5 % and selectivity of light olefins 46.8 %. Meanwhile, the catalyst stability is greatly improved after alkali metal doping during ∼ 50 h test. The characterization results of spent catalysts show that FCN-K(a) has the largest amount of active phase Fe5C2 for C–C coupling. Doping with a proper amount of K can promote the carbonization of Fe and improve the stability of the active phases.