Rather than just focusing on the catalyst itself in the electrocatalytic CO2 reduction reaction (eCO2RR), as previously reviewed elsewhere, we herein extend the discussion to the special topic of the ...microenvironment around the electrocatalytic center and present a comprehensive overview of recent research progress. We categorize the microenvironment based on the components relevant to electrocatalytic active sites, i.e., the catalyst surface, substrate, co‐reactants, electrolyte, membrane, and reactor. Supported by most of the reported articles, the relevant factors affecting the catalytic performance of eCO2RR are then discussed in detail, and existing challenges and potential solutions are mentioned. Perspectives for the future research on eCO2RR, including the integration of different microenvironment factors, the extension to industrial application by coupling with carbon capture and conversion, and separation of products, are also discussed.
This Review summarizes the impact of the microenvironment, including the catalyst surface, substrate, co‐reactants, electrolyte, membrane, and reactor, on the electrocatalytic CO2 reduction reaction (CO2RR). Different microenvironmental factors are discussed in the context of industrial applications, including coupling of CO2RR to carbon capture and conversion.
Electrochemical reduction of carbon dioxide (CO2) is an appealing approach toward tackling climate change associated with atmospheric CO2 emissions. This approach uses CO2 as the carbon feedstock to ...produce value‐added chemicals, resulting in a carbon‐neutral (or even carbon‐negative) process for chemical production. Many efforts have been devoted to the development of CO2 electrolysis devices that can be operated at industrially relevant rates; however, limited progress has been made, especially for valuable C2+ products. Herein, a nanoporous copper CO2 reduction catalyst is synthesized and integrated into a microfluidic CO2 flow cell electrolyzer. The CO2 electrolyzer exhibits a current density of 653 mA cm−2 with a C2+ product selectivity of ≈62% at an applied potential of −0.67 V (vs reversible hydrogen electrode). The highly porous electrode structure facilitates rapid gas transport across the electrode–electrolyte interface at high current densities. Further investigations on electrolyte effects reveal that the surface pH value is substantially different from the pH of bulk electrolyte, especially for nonbuffering near‐neutral electrolytes when operating at high currents.
A nanoporous copper catalyst for CO2 reduction is synthesized and integrated into a microfluidic CO2 flow cell electrolyzer with well‐engineered electrode–electrolyte interface. The CO2 electrolyzer exhibits a current density over 650 mA cm−2 with a C2+ product selectivity of ≈62% at a mild overpotential, which represents one of the highest performances that have been achieved to date.
The utility of electronically conductive metal–organic frameworks (EC‐MOFs) in high‐performance devices has been limited to date by a lack of high‐quality thin film. The controllable thin‐film ...fabrication of an EC‐MOF, Cu3(HHTP)2, (HHTP=2,3,6,7,10,11‐hexahydroxytriphenylene), by a spray layer‐by‐layer liquid‐phase epitaxial method is reported. The Cu3(HHTP)2 thin film can not only be precisely prepared with thickness increment of about 2 nm per growing cycle, but also shows a smooth surface, good crystallinity, and high orientation. The chemiresistor gas sensor based on this high‐quality thin film is one of the best room‐temperature sensors for NH3 among all reported sensors based on various materials.
A wafer‐thin sensor: The preparation of a crystalline, highly‐oriented, and thickness‐controlled thin film with an electronically conductive MOF is reported. Chemiresistive sensors based on these thin films show a high response, excellent selectivity, fast response speed, and good long‐term stability towards NH3 gas at room temperature.
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•The eCO2RR and eCORR performance on Cu catalysts was compared in a microfluidic flow cell.•Single-pass conversion in both reactions was studied under feedstock-deficient ...conditions.•The oxide-derived Cu plates exhibited a C2+ Faradaic efficiency of 83% in eCORR.
Electrochemical CO2 reduction reaction (eCO2RR) attracted much attention as potential pathways for carbon utilization and sustainable chemical production. Many efforts have been devoted into improving eCO2RR selectivity to multi-carbon (C2+) products as well as energetic efficiency, which often involve the use of a highly alkaline electrolyte. The employment of alkaline electrolyte in eCO2RR inevitably causes the formation of carbonates and loss of CO2 feedstock. Electrochemical CO reduction reaction (eCORR) has been proposed as a potential strategy to mitigate the carbonate formation issues. In this study, we conducted a detailed comparison of the electrocatalytic behaviors of Cu catalysts in both eCO2RR and eCORR using a microfluidic flow cell under alkaline electrolyte conditions. Single-pass conversion of both reactions was studied under feedstock-deficient conditions through varying the feeding rates of CO2 or CO and their partial pressures. In eCO2RR, the Cu catalysts showed a relatively low carbon efficiency (i.e., the amount of carbon ended in the desired products divided by the total amount of CO2 consumed) of less than 23% due to the formation of carbonate, whereas the catalysts exhibited a significantly higher carbon efficiency (up to 84%) in eCORR. Among all three Cu catalysts, the oxide-derived Cu plates showed the highest C2+ Faradaic efficiency of 83% at −0.59 V versus RHE in eCORR, corresponding to a C2+ partial current densities of 166 mA cm−2.
Nitrate electroreduction reaction (eNO3−RR) to ammonia (NH3) provides a promising strategy for nitrogen utilization, while achieving high selectivity and durability at an industrial scale has ...remained challenging. Herein, we demonstrated that the performance of eNO3−RR could be significantly boosted by introducing two‐dimensional Cu plates as electrocatalysts and eliminating the general carrier gas to construct a steady fluid field. The developed eNO3−RR setup provided superior NH3 Faradaic efficiency (FE) of 99 %, exceptional long‐term electrolysis for 120 h at 200 mA cm−2, and a record‐high yield rate of 3.14 mmol cm−2 h−1. Furthermore, the proposed strategy was successfully extended to the Zn‐nitrate battery system, providing a power density of 12.09 mW cm−2 and NH3 FE of 85.4 %, outperforming the state‐of‐the‐art eNO3−RR catalysts. Coupled with the COMSOL multiphysics simulations and in situ infrared spectroscopy, the main contributor for the high‐efficiency NH3 production could be the steady fluid field to timely rejuvenate the electrocatalyst surface during the electrocatalysis.
The performance of nitrate electroreduction reaction (eNO3−RR) could be significantly boosted by introducing two‐dimensional Cu plates as electrocatalysts and eliminating the general carrier gas in a microfluid flow cell to construct a steady fluid field. The developed eNO3−RR setup provided superior NH3 Faradaic efficiency, exceptional long‐term electrolysis, and could be extended to assemble efficient Zn‐nitrate batteries.
Transition metal oxides (TMOs) are widely studied for loading of various catalysts due to their low cost and high structure flexibility. However, the prevailing close‐packed nature of most TMOs ...crystals has restricted the available loading sites to surface only, while their internal bulk lattice remains unactuated due to the inaccessible narrow space that blocks out most key reactants and/or particulate catalysts. Herein, using tunnel‐structured MnO2, this study demonstrates how TMO's internal lattice space can be activated as extra loading sites for atomic Ag in addition to the conventional surface‐only loading, via which a dual‐form Ag catalyst within MnO2 skeleton is established. In this design, not only faceted Ag nanoparticles are confined onto MnO2 surface by coherent lattice‐sharing, Ag atomic strings are also seeded deep into the sub‐nanoscale MnO2 tunnel lattice, enriching the catalytically active sites. Tested for electrochemical CO2 reduction reaction (eCO2RR), such dual‐form catalyst exhibits a high Faradaic efficiency (94%), yield (67.3 mol g−1 h−1) and durability (≈48 h) for CO production, exceeding commercial Ag nanoparticles and most Ag‐based electrocatalysts. Theoretical calculations further reveal the concurrent effect of such dual‐form catalyst featuring facet‐dependent eCO2RR for Ag nanoparticles and lattice‐confined eCO2RR for Ag atomic strings, inspiring the future design of catalyst–substrate configuration.
This work demonstrates how the internal lattice sites of transition metal oxide, more specifically, MnO2, can be utilized for efficient electrochemical CO2 reduction reaction (eCO2RR) by accommodating atomic Ag catalysts within its sub‐nanoscale tunnel space. A dual‐form Ag catalyst featuring faceted Ag nanoparticles on MnO2 surface and atomic Ag strings within MnO2 tunnels is thus designed with high eCO2RR performance.
Multi-omics technology integrates gene, protein, and metabolic information to construct comprehensive gene regulatory networks. This approach aligns with the complex nature of maize storage, ...characterized by its multi-component, multi-target, and multi-pathway processes. This technology offers a holistic view for exploring nutritional changes during maize storage, addressing the challenges of high costs and inefficiency in grain storage. Despite the potential of multi-omics, current research primarily focuses on the fundamental physical and chemical changes during storage, with limited application of omics technologies to understand the underlying quality change mechanisms. This paper reviews advancements in genomics, transcriptomics, proteomics, and metabolomics, and their application to maize storage. It highlights the challenges in maize storage research and underscores the potential of multi-omics to revolutionize this field. By leveraging existing research, we propose a feasible technical route for applying multi-omics to maize storage, aiming to innovate and stimulate omics research in grain storage and establish effective, green, and safe storage strategies.
A simple method was proposed to activate alkaline Cu(OH)2 with an acidic ionomer, Nafion, to regulate its surface microenvironment, including hydrophobicity and local basicity. In particular, the ...direct complete neutralization reaction between Cu(OH)2 and Nafion in aqueous solution induces the exposing of vast anions which can exclude the in‐situ‐formed hydroxides and raise the local basicity. Remarkably, the optimal Nafion‐activated Cu(OH)2‐derived Cu can efficiently suppress the hydrogen evolution reaction (HER) and improve the selectivity for multi‐carbon products in the CO2 electroreduction reaction (eCO2RR). The H2 Faradaic efficiency (FE) decreased to 11% at a current density of 300 mA/cm2 (−0.76 V vs. RHE) in a flow cell, while the bare one with H2 had an FE of 40%. The total eCO2RR FE reaches as high as 83%, along with an evidently increased C2H4 FE of 44% as compared with the bare one (24%), and good stability (8000 s), surpassing that of most of the reported Cu(OH)2‐derived Cu. The experimental and theoretical results both show that the strong hydrophobicity and high local basicity jointly boosted the eCO2RR as acquired by felicitously introducing ionomer on the Cu(OH)2‐derived Cu surface.
A simple method was proposed to activate Cu(OH)2 with an ionomer, Nafion, to regulate its surface microenvironment, including hydrophobicity and local basicity. The optimal Nafion‐modified Cu(OH)2‐derived Cu can efficiently suppress the hydrogen evolution reaction and improve the selectivity for multi‐carbon products in the CO2 electroreduction reaction.
A noble‐metal‐free electrocatalyst is fabricated via in situ formation of nanocomposite of nitrogen‐doped graphene quantum dots (NGQDs) and Ni3S2 nanosheets on the Ni foam (Ni3S2‐NGQDs/NF). The ...resultant Ni3S2‐NGQDs/NF can serve as an active, binder‐free, and self‐supported catalytic electrode for direct water splitting, which delivers a current density of 10 mA cm−2 at an overpotential of 216 mV for oxygen evolution reaction and 218 mV for hydrogen evolution reaction in alkaline media. This bifunctional electrocatalyst enables the construction of an alkali electrolyzer with a low cell voltage of 1.58 V versus reversible hydrogen electrode (RHE) at 10 mA cm−2. The experimental results and theoretical calculations demonstrate that the synergistic effects of the constructed active interfaces are the key factor for excellent performance. The nanocomposite of NGQDs and Ni3S2 nanosheets can be promising water splitting electrocatalyst for large‐scale hydrogen generation or other energy storage and conversion applications.
A nanocomposite of nitrogen‐doped graphene quantum dots (NGQDs) with the Ni3S2 nanosheets is in situ grown on the Ni foam (Ni3S2‐NGQDs/NF). The resultant Ni3S2‐NGQDs/NF exhibits advanced electrocatalytic performance for oxygen evolution reaction, hydrogen evolution reaction, and overall water splitting reaction to produce O2 and H2.
Social presence, the ability to perceive others in an online environment, has been shown to impact student motivation and participation, actual and perceived learning, course and instructor ...satisfaction, and retention in online courses; yet very few researchers have attempted to look across contexts, disciplinary areas, or measures of social presence. This meta-analysis allowed us to look across these variables of the primary studies and identify the pattern of student outcomes (e.g., perceived learning and satisfaction) in relation to social presence through scrutiny of differences between the studies. The results showed a moderately large positive average correlation between social presence and satisfaction (r = 0.56, k = 26) and social presence and perceived learning (r = 0.51, k = 26). Large variation among correlations (86.7% for satisfaction and 92.8% for perceived learning, respectively) also indicated systematic differences among these correlations due to online course settings. We found that (a) the strength of the relationship between social presence and satisfaction was moderated by the course length, discipline area, and scale used to measure social presence; and (b) the relationship between social presence and perceived learning was moderated by the course length, discipline area, and target audience of the course. Implications and future research are discussed.
•This meta-analysis examined the relationship between Social Presence (SP) and students' satisfaction and perceived learning.•Strong positive relationship between SP and satisfaction.•Strong positive relationship between SP and perceived learning.•Course length, discipline, and SP scale significant moderators for satisfaction.•Course length, discipline, and audience significant moderators for perceived learning.
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