Search

The mechanism of how interfacial wettability impacts the CO 2 electroreduction pathways to ethylene and ethanol remains unclear. This paper describes the design and realization of controllable equilibrium of kinetic-controlled *CO and *H via modifying alkanethiols with different alkyl chain lengths to reveal its contribution to ethylene and ethanol pathways. Characterization and simulation reveal that the mass transport of CO 2 and H 2 O is related with interfacial wettability, which may result in the variation of kinetic-controlled *CO and *H ratio, which affects ethylene and ethanol pathways. Through modulating the hydrophilic interface to superhydrophobic interface, the reaction limitation shifts from insufficient supply of kinetic-controlled *CO to that of *H. The ethanol to ethylene ratio can be continuously tailored in a wide range from 0.9 to 1.92, with remarkable Faradaic efficiencies toward ethanol and multi-carbon (C 2+ ) products up to 53.7% and 86.1%, respectively. A C 2+ Faradaic efficiency of 80.3% can be achieved with a high C 2+ partial current density of 321 mA cm -2 , which is among the highest selectivity at such current densities., (© 2023. The Author(s).)

This paper describes the synthesis of ceria catalysts with octahedron, nanorod, nanocube and spindle-like morphologies via a template-free hydrothermal method. The surface morphologies, crystal plane and physical-chemical structures were investigated via field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and temperature-programmed desorption of ammonia and carbon dioxide (NH3-TPD and CO2-TPD). The catalytic performance over these ceria catalysts with different exposed planes were tested for dimethyl carbonate (DMC) synthesis from CO2 and methanol. The results showed that the spindle-like CeO2 showed the highest DMC yields, followed by nano-rods, nano-cubes and nano-octahedrons. A synergism among the exposed (111) plane, defect sites, and acid-basic sites was proposed to be crucial to obtaining the high reactivity of DMC formation.

Gas diffusion electrodes (GDEs) mediate the transport of reactants, products and electrons for the electrocatalytic CO2 reduction reaction (CO2RR) in membrane electrode assemblies. The random distribution of ionomer, added by the traditional physical mixing method, in the catalyst layer of GDEs affects the transport of ions and CO2. Such a phenomenon results in elevated cell voltage and decaying selectivity at high current densities. This paper describes a pre-confinement method to construct GDEs with homogeneously distributed ionomer, which enhances mass transfer locally at the active centers. The optimized GDE exhibited comparatively low cell voltages and high CO Faradaic efficiencies (FE > 90%) at a wide range of current densities. It can also operate stably for over 220 h with the cell voltage staying almost unchanged. This good performance can be preserved even with diluted CO2 feeds, which is essential for pursuing a high single-pass conversion rate. This study provides a new approach to building efficient mass transfer pathways for ions and reactants in GDEs to promote the electrocatalytic CO2RR for practical applications. [ABSTRACT FROM AUTHOR]

Construction of a "net‐zero‐emission" system through CO2 hydrogenation to methanol with solar energy is an eco‐friendly way to mitigate the greenhouse effect. Traditional CO2 hydrogenation demands centralized mass production for cost reduction with mass water electrolysis for hydrogen supply. To achieve continuous reaction with intermittent and fluctuating flow of H2 on a small‐scale for distributed application scenarios, modulating the catalyst interface environment and chemical adsorption capacity to adapt fluctuating reaction conditions is highly desired. This paper describes a distributed clean CO2 utilization system in which the surface structure of catalysts is carefully regulated. The Ni catalyst with unsaturated electrons loaded on In2O3 can reduce the dissociation energy of H2 to overcome the slow response of intermittent H2 supply, exhibiting a faster response (12 min) than bare oxide catalysts (42 min). Moreover, the introduction of Ni enhances the sensitivity of the catalyst to hydrogen, yielding a Ni/In2O3 catalyst with a good performance at lower H2 concentrations with a 15 times adaptability for wider hydrogen fluctuation range than In2O3, greatly reducing the negative impact of unstable H2 supplies derived from renewable energies. [ABSTRACT FROM AUTHOR]

Alloys are active in CO2 electroreduction due to their unique electronic and geometric structures. Nevertheless, CO2 reduction selectivity is still low due to the low concentration of CO2 near the catalyst surface and the high energy barrier for CO2 activation. This paper describes an AuCu nanochain aerogel (NC–AuCu) with abundant grain boundaries (GBs) that promote the accumulation and activation of CO2 for further electrochemical reduction, employing in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy and density functional theory calculations. GBs can induce a strong local electric field to concentrate the electrolyte cations and thus accumulate CO2 near the catalyst surface. NC–AuCu exhibits a superior Faradaic efficiency of close to 100% for CO2 electroreduction to CO at an extremely low overpotential of 110 mV with a high CO partial current density of 28.6 mA cm−2 in a flow cell. Coupling with a Si solar cell to convert solar energy to CO, a very high conversion efficiency of ∼13.0% is achieved. It potentially provides broad interest for further academic research and industry applications. [ABSTRACT FROM AUTHOR]

The electrochemical CO2 reduction (CO2ER) to multi‐carbon chemical feedstocks over Cu‐based catalysts is of considerable attraction but suffers with the ambiguous nature of active sites, which hinder the rational design of catalysts and large‐scale industrialization. This paper describes a large‐scale simulation to obtain realistic CuZn nanoparticle models and the atom‐level structure of active sites for C2+ products on CuZn catalysts in CO2ER, combining neural network based global optimization and density functional theory calculations. Upon analyzing over 2000 surface sites through high throughput tests based on NN potential, two kinds of active sites are identified, balanced Cu−Zn sites and Zn‐heavy Cu−Zn sites, both facilitating C−C coupling, which are verified by subsequent calculational and experimental investigations. This work provides a paradigm for the design of high‐performance Cu‐based catalysts and may offer a general strategy to identify accurately the atomic structures of active sites in complex catalytic systems. [ABSTRACT FROM AUTHOR]

Cobalt‐copper (CoCu) catalysts have industrial potential in CO/CO2 hydrogenation reactions, and CoCu alloy has been elucidated as a major active phase during reactions. However, due to elemental surface segregation and dealloying phenomena, the actual surface morphology of CoCu alloy is still unclear. Combining theory and experiment, the dual effect of surface segregation and varied CO coverage over the CoCu(111) surface on the reactivity in CO2 hydrogenation reactions is explored. The relationship between C−O bond scission and further hydrogenation of intermediate *CH2O was discovered to be a key step to promote ethanol production. The theoretical investigation suggests that moderate Co segregation provides a suitable surface Co ensemble with lateral interactions of co‐adsorbed *CO, leading to promoted selectivity to ethanol, in agreement with theory‐inspired experiments. [ABSTRACT FROM AUTHOR]

Copper can efficiently electro‐catalyze carbon dioxide reduction to C2+ products (C2H4, C2H5OH, n‐propanol). However, the correlation between the activity and active sites remains ambiguous, impeding further improvements in their performance. The facet effect of copper crystals to promote CO adsorption and C−C coupling and consequently yield a superior selectivity for C2+ products is described. We achieve a high Faradaic efficiency (FE) of 87 % and a large partial current density of 217 mA cm−2 toward C2+ products on Cu(OH)2‐D at only −0.54 V versus the reversible hydrogen electrode in a flow‐cell electrolyzer. With further coupled to a Si solar cell, record‐high solar conversion efficiencies of 4.47 % and 6.4 % are achieved for C2H4 and C2+ products, respectively. This study provides an in‐depth understanding of the selective formation of C2+ products on Cu and paves the way for the practical application of electrocatalytic or solar‐driven CO2 reduction. [ABSTRACT FROM AUTHOR]

The active sites for CO2 electroreduction (CO2R) to multi-carbon (C2+) products over oxide-derived copper (OD-Cu) catalysts are under long-term intense debate. This paper describes the atomic structure motifs for product-specific active sites on OD-Cu catalysts in CO2R. Herein, we describe realistic OD-Cu surface models by simulating the oxide-derived process via the molecular dynamic simulation with neural network (NN) potential. After the analysis of over 150 surface sites through NN potential based high-throughput testing, coupled with density functional theory calculations, three square-like sites for C–C coupling are identified. Among them, Σ3 grain boundary like planar-square sites and convex-square sites are responsible for ethylene production while step-square sites, i.e. n(111) × (100), favor alcohols generation, due to the geometric effect for stabilizing acetaldehyde intermediates and destabilizing Cu–O interactions, which are quantitatively demonstrated by combined theoretical and experimental results. This finding provides fundamental insights into the origin of activity and selectivity over Cu-based catalysts and illustrates the value of our research framework in identifying active sites for complex heterogeneous catalysts. The active sites over oxide-derived copper (OD-Cu) catalysts for CO2 electroreduction are unclear. Here, the authors show atom-level product-specific active sites on OD-Cu surface models, where planar and convex square sites are responsible for ethylene while the step square site favours alcohols generation. [ABSTRACT FROM AUTHOR]

The development of electrochemical CO2 conversion allows green carbon utilization. Formate and syngas are two typical products of electrochemical CO2 reduction, and the coproduction of these two products will maximize the energy efficiency of CO2 conversion. However, few works have successfully achieved the cogeneration of formate and syngas. This paper describes a novel strategy to maximize the efficiency of CO2 conversion through coproduction of formate and syngas on ultrasmall SnO2 nanodots (NDs) homogeneously anchored on carbon nanotubes (CNT#SnO2 NDs) electrodes. The CNT#SnO2 NDs not only decreased the adsorption energy of *OCHO but also reduced the adsorption energy difference of *COOH and *H. High energy efficiency toward formate and adjustable H2/CO ratio were obtained over a broad potential window with long‐term stability. In addition, CNT#SnO2 NDs and Ir foil were coupled together to construct an electrolyzer for electrochemical CO2 reduction reaction and oxygen evolution reaction (CO2ERR–OER), which also produced formate and syngas with 24 h stability. A promising approach is presented for the electrochemical CO2 conversion in fuel production. [ABSTRACT FROM AUTHOR]

Chemical looping provides an energy‐ and cost‐effective route for alkane utilization. However, there is considerable CO2 co‐production caused by kinetically mismatched O2− bulk diffusion and surface reaction in current chemical looping oxidative dehydrogenation systems, rendering a decreased olefin productivity. Sub‐monolayer or monolayer vanadia nanostructures are successfully constructed to suppress CO2 production in oxidative dehydrogenation of propane by evading the interference of O2− bulk diffusion (monolayer versus multi‐layers). The highly dispersed vanadia nanostructures on titanium dioxide support showed over 90 % propylene selectivity at 500 °C, exhibiting turnover frequency of 1.9×10−2 s−1, which is over 20 times greater than that of conventional crystalline V2O5. Combining in situ spectroscopic characterizations and DFT calculations, we reveal the loading–reaction barrier relationship through the vanadia/titanium interfacial interaction. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Artificial photosynthesis can be used to store solar energy and reduce CO2 into fuels to potentially alleviate global warming and the energy crisis. Compared to the generation of gaseous products, it remains a great challenge to tune the product distribution of artificial photosynthesis to liquid fuels, such as CH3OH, which are suitable for storage and transport. Herein, we describe the introduction of metallic Cu nanoparticles (NPs) on Cu2O films to change the product distribution from gaseous products on bare Cu2O to predominantly CH3OH by CO2 reduction in aqueous solutions. The specifically designed Cu/Cu2O interfaces balance the binding strengths of H* and CO* intermediates, which play critical roles in CH3OH production. With a TiO2 model photoanode to construct a photoelectrochemical cell, a Cu/Cu2O dark cathode exhibited a Faradaic efficiency of up to 53.6 % for CH3OH production. This work demonstrates the feasibility and mechanism of interface engineering to enhance the CH3OH production from CO2 reduction in aqueous electrolytes. Metallic copper nanoparticles were deposited on Cu2O films to change the product distribution of CO2 reduction in aqueous solution from the gaseous products generated on bare Cu2O to predominantly methanol. The carefully designed Cu/Cu2O interfaces balance the binding strengths of the H* and CO* intermediates, which enables efficient methanol production. [ABSTRACT FROM AUTHOR]

Abstract: Electrochemical conversion of carbon dioxide (CO2) to value‐added products is a possible way to decrease the problems resulting from CO2 emission. Thanks to the eminent conductivity and proper adsorption to intermediates, Pd has become a promising candidate for CO2 electroreduction (CO2ER). However, Pd‐based nanocatalysts generally need a large overpotential. Herein we describe that ultrathin Pd nanosheets effectively reduce the onset potential for CO by exposing abundant atoms with comparatively low generalized coordination number. Hexagonal Pd nanosheets with 5 atomic thickness and 5.1 nm edge length reached CO faradaic efficiency of 94 % at −0.5 V, without any decay after a stability test of 8 h. It appears to be the most efficient among all of Pd‐based catalysts toward CO2ER. Uniform hexagonal morphology made it reasonable to build models and take DFT calculations. The enhanced activity originates from mainly edge sites on palladium nanosheets. [ABSTRACT FROM AUTHOR]

Development of novel catalysts with high efficiency for CO2 conversion is of great research interest, because of the climate hazards caused by the gradual increase in CO2 concentration. Among various types of catalysts, semiconductors have been widely used as effective candidates for both electro- and photoelectro-CO2 conversion. Very recently, with the emerging nanotechnology and advanced characterization techniques, tremendous achievements have been made in highly efficient and clean CO2 conversion based on semiconductor catalysts. This review gives a systematic overview of this field, including the rational design of semiconductor catalysts for electro- and photoelectro-chemical CO2 conversion. Recent advances in the development of mechanism understandings on reaction pathways of CO2 and the feasibility for industrial production are discussed. Furthermore, the challenges and future perspectives of electro- and photoelectro-catalytic CO2 conversion are outlined. [ABSTRACT FROM AUTHOR]

Abstract: Carbon dioxide (CO2) reduction in aqueous solutions is an attractive strategy for carbon capture and utilization. Cuprous oxide (Cu2O) is a promising catalyst for CO2 reduction as it can convert CO2 into valuable hydrocarbons and suppress the side hydrogen evolution reaction (HER). However, the nature of the active sites in Cu2O remains under debate because of the complex surface structure of Cu2O under reducing conditions, leading to limited guidance in designing improved Cu2O catalysts. This paper describes the functionality of surface‐bonded hydroxy groups on partially reduced Cu2O(111) for the CO2 reduction reaction (CO2RR) by combined density functional theory (DFT) calculations and experimental studies. We find that the surface hydroxy groups play a crucial role in the CO2RR and HER, and a moderate coverage of hydroxy groups is optimal for promotion of the CO2RR and suppression of the HER simultaneously. Electronic structure analysis indicates that the charge transfer from hydroxy groups to coordination‐unsaturated Cu (CuCUS) sites stabilizes surface‐adsorbed COOH*, which is a key intermediate during the CO2RR. Moreover, the CO2RR was evaluated over Cu2O octahedral catalysts with {111} facets and different surface coverages of hydroxy groups, which demonstrates that Cu2O octahedra with moderate coverage of hydroxy groups can indeed enhance the CO2RR and suppress the HER. [ABSTRACT FROM AUTHOR]

Owing to the increasing emissions of carbon dioxide (CO2), human life and the ecological environment have been affected by global warming and climate changes. To mitigate the concentration of CO2in the atmosphere various strategies have been implemented such as separation, storage, and utilization of CO2. Although it has been explored for many years, hydrogenation reaction, an important representative among chemical conversions of CO2, offers challenging opportunities for sustainable development in energy and the environment. Indeed, the hydrogenation of CO2not only reduces the increasing CO2buildup but also produces fuels and chemicals. In this critical reviewwe discuss recent developments in this area, with emphases on catalytic reactivity, reactor innovation, and reaction mechanism. We also provide an overview regarding the challenges and opportunities for future research in the field (319 references). [ABSTRACT FROM AUTHOR]

Graphical abstract This paper describes the facet effect on Pd nanocrystals with the same size for CO 2 electroreduction. Highlights • Pd nanocrystals with three different facets were synthesized for CO 2 electroreduction. • A mechanism of facet effect on CO 2 electroreduction was proposed. • Pd concave cubes with {3 1 0} facets exhibited the highest CO Faradaic efficiency. • {3 1 0} facets facilitated COOH∗ formation and CO∗ desorption during the reaction. Abstract Highly selective electrochemical carbon dioxide reduction to valuable chemical products is a crucial approach to alleviate the energy crisis. To date, some noble metal based heterogeneous catalysts such as Pd exhibit high activity for electrochemical carbon dioxide reduction. However, few systematic studies of the active reaction site of these catalysts have been reported. This paper describes the facet effect on Pd nanocrystals with the same size for CO 2 electroreduction. The surface structure of Pd catalysts enclosed with {3 1 0}, {1 0 0} and {1 1 1} facets can be precisely controlled. The Pd concave cubes enclosed with high-index {3 1 0} facets show the highest CO Faradaic efficiency (FE) of 90.6%, compared with Pd cubes enclosed with {1 0 0} facets and Pd octahedrons enclosed with {1 1 1} facets. Density functional theory calculations reveal that the {3 1 0} facets of concave cubes boost the catalytic activity by facilitating the COOH∗ formation and the desorption of CO∗. [ABSTRACT FROM AUTHOR]

Abstract: Direct synthesis of diethyl carbonate from ethanol and CO2 is attractive since starting materials are cheap and easily obtainable, and the initial operational procedures are quite simple. We present results showing that Ce x Zr1−x O2 solid solution catalysts are effective and selective for producing diethyl carbonate and could be recyclable without loss of any activity. High calcination temperature is favorable based on results of catalytic test. X-ray diffraction and temperature-programmed desorption of NH3 and CO2 provide evidence indicating that catalytic properties of Ce x Zr1−x O2 are closely dependent on the crystal structures and the acid–base sites on the surface with varied Ce/Zr ratios. Strong acid–base sites on the surfaces of catalysts are unfavorable for diethyl carbonate formation. [Copyright &y& Elsevier]