Ethylene Generation Research Articles

Enhanced CO2 Electroreduction to ethylene on Cu nanocube coated with nitrogen-doped carbon shell in-situ electro-derived from metal-organic framework

Electrochemical CO2 reduction reaction (CO2RR) to ethylene is one of the most promising technologies to achieve efficient use of carbon resources and sustainable development, in which the development of an efficient and stable electrocatalyst is particularly important. In this work, we develop a catalyst in situ electro-derived from Cu-based MOF for CO2RR to ethylene. We prepared nano Cu-MOF by microwave synthesis and supported it on a Cu foil substrate as a working electrode (denoted as MOF/Cu foil). During in situ electrolysis, Cu-MOF was converted into a highly dispersed nitrogen-doped carbon-coated Cu nanocube (denoted as Cu-cube/CN), which inhibited particle agglomeration and enhanced active site exposure. At a potential of −1.15 V vs. RHE, the Faradaic efficiency (FE) of the Cu-cube/CN catalyst for ethylene is 49.6 %, significantly higher than that of the original Cu foil electrode and Cu-MOF supported on the gas diffusion layer (GDL) prepared working electrode (denoted as MOF/GDL). In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and density functional theory (DFT) calculations studies indicate that due to the electron-donating ability of the CN coating, the adsorption of *CO is enhanced, increasing the *CO coverage, lowering the reaction free energy of *CO dimerization, promoting C-C coupling and ethylene generation. This work provides new insights for the development of efficient and stable electrocatalysts for CO2RR-to-ethylene production.

Active and stable Ni-Cr oxide catalysts for oxidative dehydrogenation of ethane using CO2: Carbon cycle-assisted oxygen cycle

The CO2-assisted oxidative dehydrogenation of ethane (CO2-ODHE) is known as an ecologically beneficial process for ethylene generation and CO2 utilization. However, the quick deactivation of traditional Cr-based catalysts remains a considerable challenge. Herein, we report that a 1Ni1CrOx/ZrO2 catalyst could be high active and stable for the CO2-ODHE reaction; it showed CO2 conversion of 15.4 % and kept stable for 38 h at 600 °C, while the productivity of ethylene approached 325 μmol·min−1·gcat−1. Kinetic evaluations found a low apparent activation energy of 87.2 kJ/mol on the 1Ni1CrOx/ZrO2 catalyst. Surface Cr6+ and oxygen species were enriched to form Cr2O72− with the introduction of NiO. In addition, NiO improved the surface alkalinity and the affinity for oxygen, promoting the strong adsorption and easy activation of CO2. Importantly, Niδ+ species catalyzed the reaction between CO2 and surface-deposited carbon by redox cycling (carbon cycle), promoting Mars-van Krevelen-type carbon elimination and Cr6+ regeneration. The carbon cycle-assisted oxygen cycle on the Ni-Cr oxide catalysts could obviously enhance the carbon resistance and stable ethylene production, demonstrating potential application of Cr-based catalysts for CO2-ODHE reaction.

Modeling Diurnal and Annual Ethylene Generation from Solar-Driven Electrochemical CO2 Reduction Devices

Integrated solar fuels devices for CO2 reduction (CO2R) are a promising technology class towards achieving net-negative carbon emissions. Designing integrated CO2R solar fuels devices requires careful co-design of electrochemical and photovoltaic components as well as consideration of the diurnal and seasonal effects of solar irradiance, temperature, and other meteorological factors expected for ‘on-sun’ deployment. Using a photovoltaic-electrochemical (PV-EC) platform, we developed a temperature and potential-dependent diurnal and annual model using experimental CO2R performance of Cu-based electrocatalysts, local meteorological data from the National Solar Radiation Database (NSRD), and modeled performance of commercial c-Si PVs. We simulated diurnal product outputs with and without the effects of ambient temperature to determine gaseous product temperature sensitivity. From these outputs, we observed seasonal variation in gaseous product generation, with up to two-fold increases in ethylene productivity between the Winter and Summer, analyzed the consequences of dynamic cloud coverage, and identified periods where device cooling/heating mechanisms could be implemented to maximize ethylene generation. Finally, we modeled the annual ethylene generation for a scaled 1 MW solar farm at three different locations (Beijing, CN; Sydney, AUS; Barstow, CA) to determine the consequences of local meteorological climates on PV-EC CO2R product output, recording a maximum ethylene output of 18.5 tonne/yr at Barstow. Overall, this model presents a critical tool for streamlining the translation of experimental solar-driven electrochemical research to real-world implementation.

Selective Increase in CO2 Electroreduction to Ethanol Activity at Nanograin-Boundary-Rich Mixed Cu(I)/Cu(0) Sites via Enriching Co-Adsorbed CO and Hydroxyl Species.

Selective producing ethanol from CO2 electroreduction is highly demanded, yet the competing ethylene generation route is commonly more thermodynamically preferred. Herein, we reported an efficient CO2-to-ethanol conversion (53.5 % faradaic efficiency at -0.75 V versus reversible hydrogen electrode (vs. RHE)) over an oxide-derived nanocubic catalyst featured with abundant "embossment-like" structured grain-boundaries. The catalyst also attains a 23.2 % energy efficiency to ethanol within a flow cell reactor. In situ spectroscopy and electrochemical analysis identified that these dualphase Cu(I) and Cu(0) sites stabilized by grain-boundaries are very robust over the operating potential window, which maintains a high concentration of co-adsorbed *CO and hydroxyl (*OH) species. Theoretical calculations revealed that the presence of *OHad not only promote the easier dimerization of *CO to form *OCCO (ΔG~0.20 eV) at low overpotentials but also preferentially favor the key *CHCOH intermediate hydrogenation to *CHCHOH (ethanol pathway) while suppressing its dehydration to *CCH (ethylene pathway), which is believed to determine the remarkable ethanol selectivity. Such imperative intermediates associated with the bifurcation pathway were directly distinguished by isotope labelling in situ infrared spectroscopy. Our work promotes the understanding of bifurcating mechanism of CO2ER-to-hydrocarbons more deeply, providing a feasible strategy for the design of efficient ethanol-targeted catalysts.

Selective Increase in CO2 Electroreduction to Ethanol Activity at Nanograin‐Boundary‐Rich Mixed Cu(I)/Cu(0) Sites via Enriching Co‐Adsorbed CO and Hydroxyl Species

AbstractSelective producing ethanol from CO2 electroreduction is highly demanded, yet the competing ethylene generation route is commonly more thermodynamically preferred. Herein, we reported an efficient CO2‐to‐ethanol conversion (53.5 % faradaic efficiency at −0.75 V versus reversible hydrogen electrode (vs. RHE)) over an oxide‐derived nanocubic catalyst featured with abundant “embossment‐like” structured grain‐boundaries. The catalyst also attains a 23.2 % energy efficiency to ethanol within a flow cell reactor. In situ spectroscopy and electrochemical analysis identified that these dualphase Cu(I) and Cu(0) sites stabilized by grain‐boundaries are very robust over the operating potential window, which maintains a high concentration of co‐adsorbed *CO and hydroxyl (*OH) species. Theoretical calculations revealed that the presence of *OHad not only promote the easier dimerization of *CO to form *OCCO (ΔG~0.20 eV) at low overpotentials but also preferentially favor the key *CHCOH intermediate hydrogenation to *CHCHOH (ethanol pathway) while suppressing its dehydration to *CCH (ethylene pathway), which is believed to determine the remarkable ethanol selectivity. Such imperative intermediates associated with the bifurcation pathway were directly distinguished by isotope labelling in situ infrared spectroscopy. Our work promotes the understanding of bifurcating mechanism of CO2ER‐to‐hydrocarbons more deeply, providing a feasible strategy for the design of efficient ethanol‐targeted catalysts.

Ectoine maintains the flavor and nutritional quality of broccoli during postharvest storage

The bacterial derived osmolyte ectoine has been shown to stabilize cell structure and function, a property that may help to extend the shelf life of broccoli. The impact of ectoine on broccoli stored for 4 d at 20 °C and 90% relative humidity was investigated. Results indicated that 0.20% ectoine treatment maintained the quality of broccoli, by reducing rate of respiration and ethylene generation, while increasing the levels of total phenolics, flavonoids, TSS, soluble protein, and vitamin C, relative to control. Headspace-gas chromatography–mass spectrometry, transcriptomic and metabolomic analyses revealed that ectoine stabilized aroma components in broccoli by maintaining level of volatile compounds and altered the expression of genes and metabolites associated with sulfur metabolism, as well as fatty acid and amino acid biosynthesis pathways. These findings provide a greater insight into how ectoine preserves the flavor and nutritional quality of broccoli, thus, extending its shelf life.

Electrocatalytic reduction of CO2 to C2H4 by monometallic Cu4 cluster supported on CeO2(110) surface

Cu-based catalysts have attracted much attention in the field of electrocatalytic CO2 reduction reactions (CRR). In our current work, the electrocatalytic reduction of CO2 by Cu cluster supported on CeO2 is calculated according to the density functional theory (DFT), and some interesting results are obtained. Monometallic copper cluster electrocatalysis of CO2 produce C2 products at lower potentials. The overpotential for the generation of ethylene is much lower than those of other products. The modulation of the substrate CeO2 changed the electronic structure of the Cu clusters and constructed Cu0 and Cu+1 active sites on the catalyst surface, and the coordinated action of Cu0 and Cu+1 made the C–C coupling more likely to take place and facilitated the generation of C2 products. The results of this study help to further understand the role of Cu-based catalysts in the electrocatalytic reduction of CO2 from theoretical point of view and provide guidance for future electrocatalytic experiments based on CRR.

Site-Selective Growth of fcc-2H-fcc Copper on Unconventional Phase Metal Nanomaterials for Highly Efficient Tandem CO2 Electroreduction.

Copper (Cu) nanomaterials are a unique kind of electrocatalysts for high-value multi-carbon production in carbon dioxide reduction reaction (CO2RR), which holds enormous potential in attaining carbon neutrality. However, phase engineering of Cu nanomaterials remains challenging, especially for the construction of unconventional phase Cu-based asymmetric heteronanostructures. Here the site-selective growth of Cu on unusual phase gold (Au) nanorods, obtaining three kinds of heterophase fcc-2H-fcc Au-Cu heteronanostructures is reported. Significantly, the resultant fcc-2H-fcc Au-Cu Janus nanostructures (JNSs) break the symmetric growth mode of Cu on Au. In electrocatalytic CO2RR, the fcc-2H-fcc Au-Cu JNSs exhibit excellent performance in both H-type and flow cells, with Faradaic efficiencies of 55.5% and 84.3% for ethylene and multi-carbon products, respectively. In situ characterizations and theoretical calculations reveal the co-exposure of 2H-Au and 2H-Cu domains in Au-Cu JNSs diversifies the CO* adsorption configurations and promotes the CO* spillover and subsequent C-C coupling toward ethylene generation with reduced energy barriers.

Characteristics of Carbon Monoxide and Ethylene Generation in Mine’s Closed Fire Zone and Their Influence on Methane Explosion Limits

Methane explosions often occur during the closure process of mine fire zones, during which the concentration of combustible gases such as monoxide and ethylene produced by coal combustion dynamically changes, which changes the risk of methane explosion. Therefore, studying the gas concentration distribution and methane explosion limits during the process of mine closure is of great significance for disaster prevention and control. In this paper, a three-dimensional physical model of gob was built, and the distribution of monoxide and ethylene in the process of fire zone closure was investigated. Further, the explosion limits of methane enriched with CO and C2H4 in the closed fire zone of gob were analyzed. The results indicate that CO and C2H4 would form a small-scale accumulation phenomenon near the fire zone after the closure of the fire zone, and when the fire zone is closed for more than 15 min, the mixed combustible gases in the environment lose their explosiveness.

A note on the chemical fate of the DABCO catalyst in amine-catalyzed hypochlorite bleaching of cellulosic pulps

AbstractHypochlorous acid bleaching under amine catalysis (Hcat bleaching stage) is an optimized bleaching stage variant that is characterized by working at weakly acidic, near-neutral pH, having high bleaching efficiency, and discharging only very small amounts of chloro-organics. This study addressed the chemical fate of the used 1,4-diazabicyclo[2.2.2]octane (DABCO) catalyst. While literature proposed either homolytic or heterolytic breakage of one ethylene bridge and subsequent release of the resulting fragments as two molecules of formaldehyde, we demonstrated the degradation to proceed by ionic elimination of one ethylene bridge starting from mono-N-chlorinated DABCO. The resulting N-vinyl (enamine) derivative adds water under the release of acetaldehyde and formation of piperazine. The generation of acetaldehyde was experimentally confirmed by 2,4-dinitrophenylhydrazine trapping, directly from the processing liquid. The experimental findings agreed superbly with computations which showed the “acetaldehyde mechanism” to be much favored over the previously proposed pathways under C–C bond cleavage and release of formaldehyde. The results of this study add to a better understanding of the novel Hcat bleaching system. Graphical abstract

Targeted C-O bond cleavage of *CH2CHO at copper active sites for efficient electrosynthesis of ethylene from CO2 reduction

*CH2CHO, a pivotal intermediate in CO2 reduction reaction (CO2RR) on copper-based catalysts, hinges on the strength of Cu-C and C-O bonds for the selective production of ethanol and ethylene. However, the targeted cleavage of these bonds at Cu active sites presents a formidable challenge. In this study, we manipulated the selective C-O bond breaking at Cu through an electron enrichment strategy, steering the reaction towards ethylene synthesis. Both experimental and theoretical investigations reveal that Gd incorporation elevates electron density at Cu sites, thereby enhancing Cu-O interaction and concurrently weakening the C-O bond at the critical Cu-*O-CHCH2 bifurcation point. Notably, Gd-doped Cu2O (Gd-Cu2O) demonstrated a 1.43-fold increase in the ethylene/CO ratio relative to undoped Cu2O. This alteration steers the reaction mechanism towards ethylene generation. Our study highlights the pivotal role of regulating reaction intermediates in optimizing activity and selectivity of CO2RR in copper-based catalysts, providing valuable insights for future catalyst development.

Combined Strategies Enable Highly Selective Light Olefins and para-Xylene Production on Single Catalyst Bed.

Achieving multiple high-value-added chemical production through novel reaction processes and shape-selective catalytic strategy is the key to realizing efficient low-carbon catalytic processes. In this work, a methanol-toluene coreaction system was developed, and combined control strategies of reaction pathway guidance and shape-selective catalysis were applied for the successful production of light olefins and para-xylene on single HZSM-5 catalyst bed. Cofeeding toluene additionally provides reactive and flowing aromatic hydrocarbon pool species that change the dominant reaction pathway in the complex network of the methanol reaction on HZSM-5 and promote the formation of ethylene. For the first time, the key reaction intermediates methylmethylenecyclodiene are directly captured and identified by experimental and theoretical techniques. This helps to propose the catalytic cycle for the dominant generation of ethylene and, more importantly, enriches the methanol-to-hydrocarbons (MTH) chemistry and hydrocarbon pool mechanism. Furthermore, 0.4HZSM-5@S-1-CLD, an optimized HZSM-5 catalyst modified by the silicalite-1 epitaxial growth followed by silanization approach, realizes highly selective production of light olefins (especially ethylene) and para-xylene, while excellent reactant activity is maintained. This highly efficient coreaction route gives an important leading significance in synthesizing the raw materials for the polyolefin and polyester industries. The establishment of the combined control strategies provides a model for the joint production of multiple target chemicals in complex catalytic processes.

Low‐coordination Nanocrystalline Copper‐based Catalysts through Theory‐guided Electrochemical Restructuring for Selective CO2 Reduction to Ethylene

AbstractRevealing the dynamic reconstruction process and tailoring advanced copper (Cu) catalysts is of paramount significance for promoting the conversion of CO2 into ethylene (C2H4), paving the way for carbon neutralization and facilitating renewable energy storage. In this study, we initially employed density functional theory (DFT) and molecular dynamics (MD) simulations to elucidate the restructuring behavior of a catalyst under electrochemical conditions and delineated its restructuring patterns. Leveraging insights into this restructuring behavior, we devised an efficient, low‐coordination copper‐based catalyst. The resulting synthesized catalyst demonstrated an impressive Faradaic efficiency (FE) exceeding 70 % for ethylene generation at a current density of 800 mA cm−2. Furthermore, it showed robust stability, maintaining consistent performance for 230 hours at a cell voltage of 3.5 V in a full‐cell system. Our research not only deepens the understanding of the active sites involved in designing efficient carbon dioxide reduction reaction (CO2RR) catalysts but also advances CO2 electrolysis technologies for industrial application.

Low-coordination Nanocrystalline Copper-based Catalysts through Theory-guided Electrochemical Restructuring for Selective CO2 Reduction to Ethylene.

Revealing the dynamic reconstruction process and tailoring advanced copper (Cu) catalysts is of paramount significance for promoting the conversion of CO2 into ethylene (C2H4), paving the way for carbon neutralization and facilitating renewable energy storage. In this study, we initially employed density functional theory (DFT) and molecular dynamics (MD) simulations to elucidate the restructuring behavior of a catalyst under electrochemical conditions and delineated its restructuring patterns. Leveraging insights into this restructuring behavior, we devised an efficient, low-coordination copper-based catalyst. The resulting synthesized catalyst demonstrated an impressive Faradaic efficiency (FE) exceeding 70 % for ethylene generation at a current density of 800 mA cm-2. Furthermore, it showed robust stability, maintaining consistent performance for 230 hours at a cell voltage of 3.5 V in a full-cell system. Our research not only deepens the understanding of the active sites involved in designing efficient carbon dioxide reduction reaction (CO2RR) catalysts but also advances CO2 electrolysis technologies for industrial application.

Transcriptomic, metabolomic, and physiological analysis of two varieties of Chinese cabbage (Brassica rapa L. ssp. pekinensis) that differ in their storability

The storability of two different varieties of Chinese cabbage was evaluated. Results indicated that' Beijing New No.3′ (N3) exhibited longer storage life and better postharvest quality than' Beijing New No.1′ (N1). Relative to N1, N3 had a lower rate of fresh weight loss and rot development during the latter period of storage (125 days). Ethylene generation and the respiration rate of N3 cabbage were also lower than they were in N1 cabbage over the entire storage period. Chlorophyll (Chl) content was lower in N3 cabbage and the ACS, ACO and ACC enzyme activity were also lower than those in N1 cabbage. Additionally, the relative expression level of COL1, JAZ, MYC2, LOX, ACS, ACO, EBF, EIN3, ERF, and MKK in N1 Chinese cabbage increased, during storage in both varieties, while the relative expression of CDPK, COL1, CAML, and PAL decreased. These results provide valuable information on the storability and quality of Chinese cabbage, especially in relationship to plant hormone levels. The collective data indicate that N3 Chinese cabbage has better storability and postharvest quality than N1.

Mechanistic insights into the CO2 reduction to ethylene catalyzed by F-modified Cu/graphene composites

Fluorine-modified copper catalysts are expected to improve electrocatalytic CO2 reduction performance. In addition to active species, the cluster/support interaction in cluster-loaded catalysts has been shown to vary according to both the inherent reactivity of the metal cluster and the properties of the support. Herein, Cu loaded fluorine-doped graphene catalyst (Cu/FDG) was designed and the mechanism of Cu/FDG-catalytic reduction of CO2 into ethylene were explored. F strengthens the interaction between Cu4 and graphene surface, promoting the electron transfer of Cu clusters to the fluorine-modified graphene due to the inductive effect, which results in the formation of both Cu0 and oxidized Cuδ+ species. These species hence accelerate the adsorption of *CO, while the *CO coupling favors the generation of ethylene on the top site of Cu4 cluster due to the undercoordinated environment. The electrophilic effect guiding interface charge population can be applied to tune the reaction selectivity of Cu-catalytic reduction of CO2.

Modeling diurnal and annual ethylene generation from solar-driven electrochemical CO2 reduction devices

Integrated solar fuels devices for CO2 reduction (CO2R) are a promising technology class towards reducing CO2 emissions.

Cyclic Storage Chamber Ozonation as a Method to Inhibit Ethylene Generation during Plum Fruit Storage

This study presents a method for inhibiting ethylene production during the room-temperature storage of plum fruits, using gaseous ozone (O3). The proposed storage strategy involves the cyclic ozone treatment of fruits every 24 h with specified O3 doses. Throughout the storage period, cyclic analyses of the atmosphere composition in storage chambers were conducted, measuring ethylene and carbon dioxide levels. Several parameters describing changes in fruit quality and biochemical transformations were systematically monitored until the end of the storage process. The results clearly indicate that fruits subjected to cyclic ozone treatment with the highest O3 doses during storage exhibit the slowest ripening rate. This reduced ripening rate is primarily attributed to the downregulation of S-adenosylmethionine synthetase expression, leading to a lower ethylene concentration in the storage chambers. Other obtained results concerning soluble solid content, titratable acidity, total polyphenols, anthocyanins, and vitamin C content confirm the observations regarding the impact of ozone treatment in slowing down the fruit ripening process. The best outcomes were achieved by applying a cyclic ozone process with a 100 ppm dose for 30 min.

Applications of 1-methylcyclopropene concentrations and timing in relation to sunlight-related core browning in ‘Bartlett’ pears after extending regular-air storage

Core browning (CB) is a crucial physiological disorder that occurs in ‘Bartlett’ pears after excessive storage. Furthermore, environmental factors such as sunlight exposure cause serious related disorders during storage. 1-methylcyclopropene (1-MCP) positively delays the development of disorders, but results in poor eating quality at retail. Therefore, the primary purpose of this study was to evaluate whether sunlight exposure impacts the development of CB in ‘Bartlett’ pears and to develop optimal postharvest 1-MCP strategies for the pear industry to extend the fruit’s lifespan and deliver desirable eating quality to consumers that prefer melting texture. Over the course of a three-year evaluation, sunlight-exposed (SE) pears consistently displayed a higher CB index than the control and non-exposed (NE) pears after 150 d of regular-air (RA) storage at − 1.1 ± 0.5 °C plus 5 d at 20 ± 0.5 °C. The rapid development of CB was facilitated by decreases in ethylene production rate (EPR), peel chlorophyll content (PCC), and titratable acidity associated with increases in malondialdehyde and soluble o-quinones. Applying 0.15 and 0.3 μL L−1 1-MCP after 15 d of harvest completely protected the fruit from CB for up to 150 d of RA storage. However, these treated pears did not ripen. Lowering the 1-MCP concentration to 0.075 μL L−1 and postponing treatment to 60 d after harvest could control the CB index in the 1.53–2.33 range with a normal ripening process. For SE pears, the use of 0.15 μL L−1 1-MCP applied after 60 d of harvest reduced the CB index to 1.63 without impairing ripening capacity. It was difficult for the pear industry to monitor the EPR of 1-MCP-treated pears over the entire storage period. However, when the PCC of the treated pears fell to 0.4–0.5 IAD after 5 d of ripening, these pears could recover their ethylene generation capacity and softening behavior. Overall, the 0.15–0.075 μL L−1 1-MCP applied after 60 d of harvest provided great benefits in delaying CB development, improving storability, and retaining ripening capacity in SE ‘Bartlett’ pears following the prolonged RA storage.

Comparative transcriptome analysis of genes involved in paradormant bud release response in 'Summer Black' grape.

Grapevines possess a hierarchy of buds, and the fruitful winter bud forms the foundation of the two-crop-a-year cultivation system, yielding biannual harvests. Throughout its developmental stages, the winter bud sequentially undergoes paradormancy, endodormancy, and ecodormancy to ensure survival in challenging environmental conditions. Releasing the endodormancy of winter bud results in the first crop yield, while breaking the paradormancy of winter bud allows for the second crop harvest. Hydrogen cyanamide serves as an agent to break endodormancy, which counteracting the inhibitory effects of ABA, while H2O2 and ethylene function as signaling molecules in the process of endodormancy release. In the context of breaking paradormancy, common agronomic practices include short pruning and hydrogen cyanamide treatment. However, the mechanism of hydrogen cyanamide contributes to this process remains unknown. This study confirms that hydrogen cyanamide treatment significantly improved both the speed and uniformity of bud sprouting, while short pruning proved to be an effective method for releasing paradormancy until August. This observation highlights the role of apical dominance as a primary inhibitory factor in suppressing the sprouting of paradormant winter bud. Comparative transcriptome analysis revealed that the sixth node winter bud convert to apical tissue following short pruning and established a polar auxin transport canal through the upregulated expression of VvPIN3 and VvTIR1. Moreover, short pruning induced the generation of reactive oxygen species, and wounding, ethylene, and H2O2 collectively acted as stimulating signals and amplified effects through the MAPK cascade. In contrast, hydrogen cyanamide treatment directly disrupted mitochondrial function, resulting in ROS production and an extended efficacy of the growth hormone signaling pathway induction.