CO2 Production Rate Research Articles

Bismuth-based photocatalysts enhanced by sulfur/oxygen vacancies for the selective reduction of carbon dioxide into methane

Reducing carbon dioxide (CO2) into methane (CH4) through photocatalysis technology can effectively decrease carbon emissions and ease the energy crisis. However, the low photocatalytic efficiency and high electron-hole recombination rates still hinder the large-scale utilization of photocatalysis. Vacancy engineering can reduce electron-hole pair complexation, however, the effects of oxygen (O) and sulfur (S) vacancies on the CO2 reduction properties of bismuth (Bi)-based photocatalysts are unclear. This study prepared different Bi-based photocatalysts, including α-Bi2O3, α-Bi2O3-X, Bi2S3, and Bi2S3-X. The introduction of vacancies was found to greatly increase the specific surface areas, effectively reduce electron-hole recombination, decrease charge transfer resistance, and enhance electron transfer, leading to enhanced CH4 production. Comparatively, Bi2S3-X has substantially demonstrated a superior efficiency in the photocatalytic conversion of CO2 to CH4 compared to Bi2S3, while α-Bi2O3-X exhibited slightly higher than α-Bi2O3. There are more S vacancies in Bi2S3-X (x=0.581) than O vacancies in α-Bi2O3-X (x=0.329), leading to its superior photocatalytic activity, with CO and CH4 production rates of 3.706 μmol·g−1·h−1 and 7.697 μmol·g−1·h−1, respectively. Moreover, the CH4 selectivity of Bi2S3-X reaches 67.50 %, which is 1.67 times that of α-Bi2O3-X. Therefore, Bi2S3-X holds great promise as a photocatalyst for CO2 reduction. This work proves that in Bi-based photocatalyst, S vacancy is more effective than O vacancy in enhancing the selective reduction of CO2 to CH4, offering a pathway for achieving selective CO2 reduction to CH4.

Tip-like copper sites on high curvature supports for non-covalent to covalent interaction tuning in CO2 photoreduction

Single-atom engineering offers a promising method to transform CO2 into high-value chemicals. The local coordination structure design of the metal-support is crucial for overcoming slow reaction kinetics. In this study, Cu single atoms are immobilized on curved Bi12O17Br2 surface to create a tip-like metal site structure named Cutip-Bi12O17Br2. Due to the high curvature Bi12O17Br2 surface with tensile strain, the tip Cu creates significant electronegativity differences between adjacent Bi atomic sites, creating the vigorous polarization centers. The strong charge redistribution character of tip asymmetric Cu-Bi site favor the polarization of CO bond in nonpolar CO2 and adjust the noncovalent to covalent interaction of reaction intermediates. Benefiting from these features, the optimized Cutip-Bi12O17Br2 enhance the CO production rate by a factor of 34 relative to bulk-Bi12O17Br2, reaching a rate of 96.99 μmol g−1 h−1. This work provides a comprehensive understanding of the structural regulation of single-atom on high curvature surface for CO2 photoreduction.

Monolithic Nitrogen-Doped Carbon Electrode with Hierarchical Porous Structure for Efficient Electrochemical CO2 Reduction.

N-doped carbon materials have garnered extensive development in electrochemical CO2 reduction due to their abundant sources, high structural plasticity, and excellent catalytic performance. However, the use of powder carbon materials for electrocatalytic reactions limits their current density and mechanical strength, which pose challenges for industrial applications. In this study, we synthesized a monolithic N-doped carbon electrode with high mechanical strength for efficient electrochemical reduction of CO2 to CO through a simple pyrolysis method, using phenolic resin as the precursor and ZIF-8 as the sacrificial template. At 900 °C, the decomposition of ZIF-8 and the volatilization of Zn atoms promote the formation of a hierarchical porous structure in the carbon matrix, characterized by macropores with extended mesoporous channels. Simultaneously, N active species derived from ZIF-8 are effectively generated around the pores and fully exposed. The efficient mass transfer facilitated by the hierarchical porous structure and high activity of exposed nitrogen species enables efficient conversion of CO2 to CO. When the ZIF-8 content is 30%, the catalyst achieves a Faradaic efficiency of 88.9% for CO at a low potential of -0.7 V (vs RHE), with a CO production rate of 244.05 μmol h-1 cm-2. After 50 h of potentiostatic electrolysis, the current density and FECO remain stable. This work not only provides a strategy for the synergistic effects of hierarchical porous structures and nitrogen doping but also offers an effective method to avoid using powder binders and prepare integrated, stable monolithic electrodes.

Development of Ce-doped NH2-UiO-66(Zr) photocatalysts for efficient CO2 reduction in an aqueous system

A series of bimetallic NH2-UiO-66(Zr/Ce) catalysts with varying Zr/Ce molar ratios were synthesized using a straightforward solvothermal method. Among the tested samples, NH2-UiO-66(Zr/Ce1:1) demonstrated superior performance, attributed to its optimized electronic structure, enhanced CO2 adsorption capacity, and efficient separation of photogenerated electron-hole pairs, outperforming the NH2-UiO-66(Zr) variant. The NH2-UiO-66(Zr/Ce1:1) exhibited a bandgap of 2.67 eV, CO2 adsorption capacity of 65.85 cm3/g, and a photocurrent density of 0.43 μA·cm−2. This catalyst achieved achieving a CO production rate of 30.04 μmol·g−1·h−1, representing a 1.66-fold improvement over NH2-UiO-66(Zr), with CO selectivity increasing from 95.2 % to 97.2 %. The results underscore the efficacy of Zr/Ce bimetallic NH2-UiO-66 for CO2 reduction, highlighting the potential of structural modifications in NH2-UiO-66 to enhance photocatalytic performance. This study provides valuable insights into the design and development of advanced catalysts for efficient and sustainable CO2 reduction.

Synthesis of a novel biomass-based flame retardant featuring vinyl-terminated chemical cross-linking and application in flame retardancy, smoke suppression, toxicity reduction and mechanical enhancement of PAN composite fibers

To develop green and efficient polyacrylonitrile (PAN) fibers with excellent fire safety properties, a new biomass-based flame retardant (PPC@VA) with vinyl-terminated groups was prepared based on the reaction of hexachlorocyclotriphosphonitrile, teat polyphenols, ethylenediamine and vinylphosphonic acid. Subsequently, it was mixed with spinning solution to obtain PPC@VA/PAN through wet spinning, which were then chemically cross-linked via thermal initiation to achieve CC-PPC@VA/PAN fibers. CC-PPC@VA/PAN showed a significant improvement in flame retardancy with a limiting oxygen index value of 32.5 %. The peak of smoke production rate, total smoke production and CO production rate were lowered by 81.9 %, 77.8 % and 91.3 %. Besides, the hazardous gas HCN was greatly suppressed. Owing to the macromolecular entanglement, hydrogen bonding and covalent cross-linking, CC-PPC@VA/PAN improved elongation at break and tensile strength by 19.2 % and 72.1 %. Also, chemical cross-linking contributed to decrease the migration of P/N-based flame retardants, lower the potential risk of water eutrophication and increased the service life of the fibers.

Precisely Constructing Molecular Junctions in Hydrogen-Bonded Organic Frameworks for Efficient Artificial Photosynthetic CO2 Reduction.

The development of artificial photocatalysts to convert CO2 into renewable fuels and H2O into O2 is a complex and crucial task in the field of photosynthesis research. The current challenge is to enhance photogenerated charge separation, as well as to increase the oxidation capability of materials. Herein, a molecular junction-type porphyrin-based crystalline photocatalyst (Ni-TCPP-TPyP) was successfully self-assembled by incorporating a nickel porphyrin complex as a reduction site and pyridyl porphyrin as an oxidation site via hydrogen bonding and π-π stacking interactions. The resulting material has a highly crystalline structure, and the formation of inherent molecular junctions can accelerate photogenerated charge separation and transport. Thus, Ni-TCPP-TPyP achieved an excellent CO production rate of 309.3 μmol g-1 h-1 (selectivity, ~100 %) without the use of any sacrificial agents, which is more than ten times greater than that of single-component photocatalyst (Ni-TCPP) and greater than that of the most organic photocatalysts. The structure-function relationship was investigated by femtosecond transient absorption spectroscopy and density functional theory calculations. Our work provides new insight for designing efficient artificial photocatalysts, paving the way for the development of clean and renewable fuels through the conversion of CO2 using solar energy.

Precisely Constructing Molecular Junctions in Hydrogen‐Bonded Organic Frameworks for Efficient Artificial Photosynthetic CO2 Reduction

AbstractThe development of artificial photocatalysts to convert CO2 into renewable fuels and H2O into O2 is a complex and crucial task in the field of photosynthesis research. The current challenge is to enhance photogenerated charge separation, as well as to increase the oxidation capability of materials. Herein, a molecular junction‐type porphyrin‐based crystalline photocatalyst (Ni‐TCPP‐TPyP) was successfully self‐assembled by incorporating a nickel porphyrin complex as a reduction site and pyridyl porphyrin as an oxidation site via hydrogen bonding and π–π stacking interactions. The resulting material has a highly crystalline structure, and the formation of inherent molecular junctions can accelerate photogenerated charge separation and transport. Thus, Ni‐TCPP‐TPyP achieved an excellent CO production rate of 309.3 μmol g−1 h−1 (selectivity, ~100 %) without the use of any sacrificial agents, which is more than ten times greater than that of single‐component photocatalyst (Ni‐TCPP) and greater than that of the most organic photocatalysts. The structure‐function relationship was investigated by femtosecond transient absorption spectroscopy and density functional theory calculations. Our work provides new insight for designing efficient artificial photocatalysts, paving the way for the development of clean and renewable fuels through the conversion of CO2 using solar energy.

Light-Driven Reverse Water Gas Shift Reaction with 1000-H Stability on High-Entropy Alloy Catalysts.

Highly stable and active catalysts are of significant importance and a longstanding challenge for a number of industrial chemical transformations. Here, motivated by the principle of the high entropy-stabilized structure, high-entropy alloy-loaded porous TiO2 as an efficient and sintering-resistant catalyst for the light-driven reverse water gas‒shift reaction without external heating is synthesized. The optimized CoNiCuPdRu/TiO2 catalyst exhibits a long-term stability of 1000h (1.23molgmetal -1h-1 CO production rate, >99% high selectivity). In situ characterizations confirm that the slow diffusion effect of high-entropy alloys endows the catalyst with excellent structural stability. The CO adsorption measurements and theoretical calculations consolidate that the hydrogen surface coverage weakens CO adsorption on the catalyst surface. Two major problems of catalyst deactivation - sintering and poisoning, are handled in one case, which synergistically enable unparalleled stability. This work provides new guidance for the rational design of ultradurable harsh-condition operation catalysts for industrial catalysis.

In-situ construction of Bi-MOF-derived S-scheme BiOBr/CdIn2S4 heterojunction with rich oxygen vacancy for selective photocatalytic CO2 reduction using water

In this study, a highly selective MOF-BiOBr/CdIn2S4 (MOF-BiOBr/CIS) heterostructure with CdIn2S4 nanosheets grown in situ on the tubular structure derived from Bi-MOF-based BiOBr was successfully constructed using a hydrothermal method. Under simulated solar light without sacrificial or photosensitizing agents, the 20-MOF-BiOBr/CIS composite exhibited excellent photocatalytic CO2 performance, achieving production rates of 30.18 μmol‧g−1‧h−1 for CO and 1.50 μmol‧g−1‧h−1 for CH4. Compared to pure MOF-BiOBr and CdIn2S4, the CO production rates were increased by approximately 9 and 116 times, respectively. It was revealed that the 20-MOF-BiOBr/CIS composite with rich oxygen vacancy exhibited close interfacial contact and efficient charge transfer. The formation of MOF-BiOBr/CdIn2S4 heterojunction thereby provided efficient CO2 photocatalytic reduction. The CO selectivity of 20-MOF-BiOBr/CIS reached 83.4 %, and the MOF-BiOBr/CIS heterojunction exhibited good stability over multiple cycles. Furthermore, a mechanism for enhanced photocatalytic CO2 reduction by the MOF-BiOBr/CIS heterojunction was also proposed.

A C-modified engineering strategy of porous In2O3 catalysts for point-concentrated solar-driven photothermal CO2 hydrogenation

The solar-driven photothermal CO2 conversion serves as an effective approach for addressing the substantial challenges of energy crises and global environmental issues. In this work, various forms of In2O3 catalysts, including In2O3-c, In2O3-r, In2O3-s, and porous spherical In2O3, along with a C-modified porous spherical In2O3 catalyst (C-In2O3), were successfully synthesized through a hydrothermal method. An in-depth analysis was conducted to evaluate the performance of these catalysts in the point-concentrated solar-driven photothermal CO2 hydrogenation. As a result, the porous C-In2O3 catalyst exhibited a superior CO2 conversion rate of approximately 13.2 % under simulated sunlight irradiation, with a light intensity of 44.6 mW/cm2. Notably, all catalysts demonstrated nearly 100 % selectivity towards CO (CO production rate of around 8.51 mmol gcat−1h−1) during the photothermal catalytic reaction, without any formation of CH4. The outstanding performance of the C-In2O3 catalyst was attributed to the modification of In2O3 band structure by the incorporation of C, which significantly enhanced the intensive solar light absorption of the catalyst. Furthermore, incorporating C into In2O3 substantially augments its basic strength and significantly elevates the quantity of basic sites, thereby endowing it with outstanding CO2 adsorption and conversion capabilities. This work provides a C-modified engineering strategy to design efficient photothermal catalysts for boosting point-concentrated photothermal CO2 hydrogenation.

Ti[sbnd]F bridged IL-CuCQDs-F/TiO2 inverse opal composite for boosting CO2 visible-photo reduction via slow photon effect

Photocatalytic reduction of CO2 exhibits unsatisfactory photocatalytic performance owing to the inefficient separation of photogenerated electron-hole pairs, low CO2 capture efficiency and limited visible light absorption on most photo-catalysts. Herein, TiF bridged IL-CuCQDs-F/TiO2 inverse opal composite (IO-CFTi) was constructed for boosting CO2 visible-photo reduction via slow photo effect. In this work, ethylenediaminetetraacetic acid (EDTA(Cu)) and imidazole ionic liquid 1-(2-Hydroxyethyl)-3-methylimidazolium tetrafluoroborate ([HOEtMIM][BF4]) were employed to confine grow of IL-CuCQDs-F within TiO2 inverse opal supporter via TiF bonds connection. Unique IL-CuCQDs-F efficiently expended light absorption towards visible region, and the confined growth of IL-CuCQDs-F within the TiO2 inverse opal cavity achieved the photoelectric conversion and efficient CO2 capture. Moreover, their TiF bonding interface of IO-CFTi assisted photogenerated electron transportation from TiO2 to CO2 for its reduction in this system. Consequently, IO-CFTi achieved a substantially increased CO production rate of 78.1 μmol·h−1·g−1 with 98 % selectivity. This improved performance in CO2 photoreduction positions the nanocomposite as a promising material for preservation of the environment and conversion of energy.

Performance of empirical and model-based classifiers for detecting sucrase-isomaltase inhibition using the 13C-sucrose breath test

The13C-sucrose breath test (13C-SBT) has been proposed to estimate sucrase-isomaltase (SIM) activity and is a promising test for SIM deficiency, which can cause gastrointestinal symptoms, and for intestinal mucosal damage caused by gut dysfunction or chemotherapy. We previously showed how various summary measures of the13C-SBT breath curve reflect SIM inhibition. However, it is uncertain how the performance of these classifiers is affected by test duration. We leveraged13C-SBT data from a cross-over study in 16 adults who received 0, 100, and 750 mg of Reducose, an SIM inhibitor. We evaluated the performance of a pharmacokinetic-model-based classifier,ρ, and three empirical classifiers (cumulative percent dose recovered at 90 min (cPDR90), time to 50% dose recovered, and time to peak dose recovery rate), as a function of test duration using receiver operating characteristic (ROC) curves. We also assessed the sensitivity, specificity, and accuracy of consensus classifiers. Test durations of less than 2 h generally failed to accurately predict later breath curve dynamics. The cPDR90 classifier had the highest ROC area-under-the-curve and, by design, was robust to shorter test durations. For detecting mild SIM inhibition,ρhad a higher sensitivity. We recommend13C-SBT tests run for at least a 2 h duration. Although cPDR90 was the classifier with highest accuracy and robustness to test duration in this application, concerns remain about its sensitivity to misspecification of the CO2production rate. More research is needed to assess these classifiers in target populations.

Electronic interaction and band alignment between Cu sub-nanometric clusters and ZnIn2S4 nanosheets towards selective photoreduction of CO2 to CO

Engineering the electronic properties of heterogeneous photocatalysts with charge transfer regulated is an effective strategy to boost their CO2 reduction activity. Here, we drew inspiration from the strong metal-support interaction effect, and fabricated ZnIn2S4 supported-Cu sub-nanometric clusters photocatalyst. Within this catalyst, the formed CuS bond would redistribute interfacial charge, resulting in diverse chemical states of Cu atoms and the establishment of Ohmic contact between ZIS and Cu. The built-in electric field of such Ohmic contact benefited the migration of photoexcited electrons from ZIS to Cu. Further mechanistic studies unveiled the crucial role of positively charged Cu atom near the interface in facilitating H2O dissociation, and its adjacent Cu atom at the top-surface adopting a distinct chemical state could activate linear CO2 molecule into a bent configuration. These features substantially lowered energy barriers for CO2 adsorption and subsequent *COOH formation, and Cu-ZIS, accordingly, exhibited a remarkable CO production rate of 60.2 μmol g-1h−1, approximately 20.8-fold enhancement compared to ZIS counterpart.

Synthesis of metal-phenanthroline-modified hypercrosslinked polymer for enhanced CO2 capture and conversion via chemical and photocatalytic methods under ambient conditions

Catalytic conversion of CO2 into valuable chemicals is a promising approach to mitigate the greenhouse effect and alleviate energy shortages. Hypercrosslinked polymers (HCPs) offer a scalable and stable platform for this conversion, but they often suffer from low CO2 adsorption and activation capabilities, necessitating high temperatures and pressures for effectiveness. To overcome these limitations, nitrogen-based CO2-philic active sites have been integrated into the structure of HCPs, enhancing CO2 attraction and leading to superior adsorption performance. The incorporation of cobalt ions further bolsters CO2 affinity, with HCP-PNTL-Co-B achieving the highest observed adsorption heat of 33.0 kJ·mol-1 alongside a substantial 2.0 mmol·g-1 CO2 uptake. These modified HCPs exhibit higher yields and reaction rates in cycloaddition reactions with cocatalyst tetrabutylammonium bromide at room temperature and atmospheric pressure, while HCP-1,10-phenanthroline (PNTL)-Co-B demonstrates a higher CO production rate (2,173 μmol·g-1·h-1) and selectivity (84%) in photocatalytic reduction reaction. This research has successfully achieved outstanding carbon dioxide capture and conversion performance at room temperature and atmospheric pressure by introducing CO2-philic active sites and cobalt ions into HCPs via facile one-step polymerization. This study provides a new method to design highly efficient organic catalysts for CO2 conversion.

Regulating crystal phase of TiO2 to enhance catalytic activity of Ni/TiO2 for solar-driven dry reforming of methane

Ni/TiO2 catalyst is widely employed for photo-driven DRM reaction while the influence of crystal structure of TiO2 remains unclear. In this work, the rutile/anatase ratio in supports was successfully controlled by varying the calcination temperature of anatase-TiO2. Structural characterizations revealed that a distinct TiOx coating on the Ni nanoparticles (NPs) was evident for Ni/TiO2-700 catalyst due to strong metal-support interaction. It is observed that the TiOx overlayer gradually disappeared as the ratio of rutile/anatase increased, thereby enhancing the exposure of Ni active sites. The exposed Ni sites enhanced visible light absorption and boosted the dissociation capability of CH4, which led to the much elevated catalytic activity for Ni/ TiO2-950 in which rutile dominated. Therefore, the catalytic activity of solar-driven DRM reaction was significantly influenced by the rutile/anatase ratio. Ni/TiO2-950, characterized by a predominant rutile phase, exhibited the highest DRM reactivity, with remarkable H2 and CO production rates reaching as high as 87.4 and 220.2 mmol/(g·h), respectively. These rates were approximately 257 and 130 times higher, respectively, compared to those obtained on Ni/TiO2-700 with anatase. This study suggests that the optimization of crystal structure of TiO2 support can effectively enhance the performance of photothermal DRM reaction.

Morphology effects of CeO2 on the performance of CaO-Cu/ CeO2 for integrated CO2 capture and conversion to CO

CeO2 support inhibits CaO sintering, and oxygen vacancy influences CO2 hydrogenation performance, making CeO2 widely applied in Integrated CO2 capture and in-situ conversion technology for reverse water–gas shift (ICCC-RWGS). Oxygen vacancy concentration was dependent on the morphology of CeO2, which would affect metal dispersion and CO2 hydrogenation conversion. However, Very little is known about the morphology effect of CeO2 on the carbon capture and in-situ hydrogenation performance of DFMs. Here, Cu/CeO2 with different CeO2 morphologies was synthesized, and high Cu dispersion was achieved on Cu/CeO2-R, exhibiting the best CO2 hydrogenation performance. Integrated Cu/CeO2 with CaO by physical mixing method, CaO-Cu/CeO2 was used to investigate the morphology effects of CeO2 on the performance of CaO-Cu/CeO2 for integrated CO2 capture and conversion to CO. CaO-Cu/CeO2-R exhibited the best capture-hydrogenation performance (CO2 conversion rate of 75 %, CO production rate of 9.72 mmol/g). The CeO2-R provided more surface oxygen vacancies, enhancing carbonate hydrogenation. The larger specific surface area and {110} crystal plane of CeO2-rod enhanced Cu dispersion, and the smaller particle size of CeO2-R enhanced its interaction with CaO, improving the cyclic stability of CaO-Cu/CeO2-R. The hydrogenation performance of CaO-Cu/CeO2 was dependent on the morphology of CeO2, providing insights into the design of high-activity metal catalytic components in ICCC-RWGS.

Fire-resistant and mechanically-robust phosphorus-doped MoS2/epoxy composite as barrier of the thermal runaway propagation of lithium-ion batteries

Thermal runaway propagation (TRP) is an utmost safety issue in battery modules owing to its derivative accidents of fire or explosion. This study develops a novel flame-retardant epoxy resin (EP) board to prevent the battery TRP. The phosphorus doped MoS2 nanowires (PR-MoS2) is designed and incorporated into EP matrix to acquire EP/3.0 PR-MoS2 composite. The composite shows 159.4 % increase in char yield, 56.7 % decrease in peak heat release rate, 56.6 % reduction in peak CO production rate. By using EP/PR-MoS2-3 (EP/3.0 PR-MoS2 composite with thickness of 3 mm) between 103450-pouch cells, TRP can be effectively stopped. Meanwhile, the temperature of surviving battery remains below 100 °C. Of note, the minimum changes in internal crystal structure, chemical composition and electrochemical characteristics are discerned for the surviving battery. This research will offer inspirations for the design of TRP suppression materials, guaranteeing the safety the battery.

Hollow porous silica nanoreactors encapsulating VOx-decorated Pt nanoparticles for the reverse water–gas shift reaction

Reverse water–gas shift (RWGS) reaction is a desirable strategy for achieving CO2 utilization and enhancing CO production. Due to the endothermic nature and the chemical equilibrium of this reaction, the reaction is typically conducted at high temperatures (300 ∼ 1000 °C); however, high temperature conditions lead to the sintering of the catalyst, resulting in a catalyst deactivation. Herein we report the synthesis of a metal oxide (V or Mo oxide)-decorated Pt nanoparticles encapsulated in hollow porous silica nanoreactors (HPSNs) by a W/O micro-emulsion system using branched poly(ethyleneimine) (PEI) as a sacrificial metal–ligand. The HPSNs encapsulating VOx-decorated Pt nanoparticles (Pt-VOx@HPSNs) afforded a 1.8-fold increased activity in RWGS reaction at 500 °C compared with Pt@HPSNs with a net CO production rate of 1140.3 mmol/gcat/h and with nearly 100 % CO selectivity. In situ XAFS measurement and reaction kinetic analysis reveal that the interplay of Pt nanoparticles and the decorated V oxide, which simultaneously activate H2 and CO2, respectively, leads to a lowering of the activation energy and a faster CO production rate. Furthermore, the Pt-VOx@HPSNs catalyst retains over 92 % activity after 50 h of continuous operation at 500 °C with the aid of a protective silica shell. This work offers a strategy for the design and development of an efficient and stable heterogeneous catalyst for RWGS reactions.

Integrated Experiment-Theory Framework for Studying Mass Transport Effects in Electrochemical CO2 Reduction on Copper

Electrochemical carbon dioxide reduction (eCO2R) has emerged as a promising approach to produce high-value fuels and chemicals using renewable energy sources. In particular, Cu catalysts can convert CO2 to a wide range of hydrocarbon and oxygenate products, including CO, formate, ethanol and ethylene. However, the activity and selectivity of eCO2R is highly dependent on mass transport and the corresponding reaction microenvironment present under operating conditions. In this talk, we present an integrated framework that combines experiments with computational fluid dynamics (CFD) and density functional theory (DFT) based microkinetic modeling to predict the effect of varying mass transport on eCO2R in a custom-designed flow cell. The flow cell is designed with multiple electrolyte jets impinging onto the electrocatalyst surface for rapid and homogeneous reactant transport. We first demonstrate the effect of mass transport in a flow cell architecture by controlling the flow rate of CO2-saturated 0.1 M KHCO3 to a Cu electrocatalyst. Significant increases in the production rates of formate and CO are observed with increasing flow rate, as well as an enhancement in multi-carbon products at high overpotentials. Increasing flow rate promotes hydrogen evolution at low overpotentials but has little effect at large overpotentials, suggesting a transition from HCO3 - to water as the dominant proton donor with increasing overpotential. CFD simulations are employed to model the distribution of boundary layer thicknesses within the flow cell, which subsequently set the boundary conditions for the coupled 1D transport-microkinetic model. The calculated boundary layer thickness values are corroborated by experimentally measured transport-limited currents. Our model successfully predicts experimentally observed trends in selectivity with mass transport, such as an increase in the production of ethylene and ethanol at high flow rates due to enhanced CO2 transport. The slight suppression of hydrogen reduction at higher flow rates due to an increase in *CO coverage is also predicted and supported by experimental results. This work demonstrates the importance of incorporating transport processes in the CFD-DFT coupled modeling of device performance for electrochemical CO2 reduction.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL release number: LLNL-ABS-857566.

Rationally Designed S-Scheme CeO2/g-C3N4 Heterojunction for Promoting Visible Light Driven CO2 Photoreduction into Syngas.

Exploring low-cost visible light photocatalysts for CO2 reduction to produce proportionally adjustable syngas is of great significance for meeting the needs of green chemical industry. A S-Scheme CeO2/g-C3N4 (CeO2/CN) heterojunction was constructed by using a simple two-step calcination method. During the photocatalytic CO2 reduction process, the CeO2/CN heterojunction can present a superior photocatalytic performance, and the obtained CO/H2 ratios in syngas can be regulated from 1 : 0.16 to 1 : 3.02. In addition, the CO and H2 production rate of the optimal CeO2/CN composite can reach 1169.56 and 429.12 μmol g-1 h-1, respectively. This superior photocatalytic performance is attributed to the unique S-Scheme photogenerated charge transfer mechanism between CeO2 and CN, which facilitates rapid charge separation and migration, while retaining the excellent redox capacity of both semiconductors. Particularly, the variable valence Ce3+/Ce4+ can act as electron mediator between CeO2 and CN, which can promote electron transfer and improve the catalytic performance. This work is expected to provide a new useful reference for the rational construction of high efficiency S-Scheme heterojunction photocatalyst, and improve the efficiency of photocatalytic reduction of CO2, promoting the photocatalytic reduction of CO2 into useful fuels.