Tuning the Selectivity of Carbon Dioxide Electroreduction toward Ethanol on Oxide-Derived Cu_<i>x</i>Zn Catalysts

The electrochemical reduction of carbon dioxide (CO₂) to ethanol (C₂H₅OH) and ethylene (C₂H₄) using renewable electricity is a viable method for the production of these commercially vital chemicals. Copper (Cu) and its oxides are by far the most effective electrocatalysts for this purpose. However, the formation of ethanol using these catalysts is generally less favored in comparison to that of ethylene. In this work, we demonstrate that the selectivity of CO₂ reduction toward ethanol could be tuned by introducing a cocatalyst to generate an in situ source of mobile CO reactant. Cu-based oxides with different amounts of Zn dopants (Cu, Cu₁₀Zn, Cu₄Zn, and Cu₂Zn) were prepared and used as catalysts under ambient pressure in aqueous 0.1 M KHCO₃ electrolyte. By varying the amount of Zn in the bimetallic catalysts, we found that the selectivity of ethanol versus ethylene production, defined by the ratio of their Faradaic efficiencies (FE_ethanol/FE_ethylene), could be tuned by a factor of up to ∼12.5. Ethanol formation was maximized on Cu₄Zn at −1.05 V vs RHE, with a remarkable Faradaic efficiency and current density of 29.1% and −8.2 mA/cm², respectively. The Cu₄Zn catalyst was also catalytically stable for the production of ethanol for at least 5 h. The importance of Zn as a CO-producing site was demonstrated by performing CO₂ reduction on Cu–Ni and Cu–Ag bimetallic catalysts. Operando Raman spectroscopy revealed that the as-deposited Cu-based oxide films were reduced to the metallic state during CO₂ reduction, after which only signals belonging to CO adsorbed on Cu sites were recorded. This showed that the reduction of CO₂ probably occurred on metallic sites rather than on metal oxides. A two-site mechanism to rationalize the selective reduction of CO₂ to ethanol is proposed and discussed

Continuous Production of Ethylene from Carbon Dioxide and Water Using Intermittent Sunlight

The large-scale deployment of efficient artificial photosynthesis systems to convert carbon dioxide (CO₂) into carbon-based fuels and chemical feedstocks holds great promise as a way to ensure a carbon neutral cycle. While catalysts have been developed for the pertinent half-reaction of CO₂ reduction to C₂ molecules, an integrated system for this purpose has never been designed and built. In this work, we demonstrate an energetically efficient formation of ethylene directly from CO₂ and water (H₂O) using solar energy at room temperature and pressure. A two-electrode cell (electrolyzer) was designed, and cell parameters such as electrolyte and voltage were optimized. Oxide-derived copper (Cu) and iridium oxide (IrO_<i>x</i>) were used as electrocatalysts respectively in the cathode and anode. Coupling this electrolyzer with silicon solar panels under laboratory 1 sun illumination (100 mW/cm²), we show that CO₂ could be facilely reduced to ethylene with a faradaic efficiency of 31.9%, partial current density of 6.5 mA/cm², and a solar-to-ethylene energy efficiency of 1.5%. When liquid fuels such as ethanol and <i>n</i>-propanol were included, the total solar-to-fuel efficiency was 2.9%. These outstanding figures-of-merits are the state-of-the-art. We also introduced insoluble chelating agents in the electrolyte to capture contaminants such as dissolved iridium ions, and thus significantly improved the longevity of the electrolyzer. Compared to previously reported solar-to-fuel setups which were only tested under simulated sunlight, our system, when coupled with a rechargeable battery, could run and produce ethylene continuously using only intermittent natural sunlight

Mechanistic Insights into the Enhanced Activity and Stability of Agglomerated Cu Nanocrystals for the Electrochemical Reduction of Carbon Dioxide to <i>n</i>‑Propanol

The reduction of carbon dioxide (CO₂) to <i>n-</i>propanol (CH₃CH₂CH₂OH) using renewable electricity is a potentially sustainable route to the production of this valuable engine fuel. In this study, we report that agglomerates of ∼15 nm sized copper nanocrystals exhibited unprecedented catalytic activity for this electrochemical reaction in aqueous 0.1 M KHCO₃. The onset potential for the formation of <i>n-</i>propanol was 200–300 mV more positive than for an electropolished Cu surface or Cu⁰ nanoparticles. At −0.95 V (vs RHE), <i>n-</i>propanol was formed on the Cu nanocrystals with a high current density (<i>j</i>_{<i>n</i>‑propanol}) of −1.74 mA/cm², which is ∼25× larger than that found on Cu⁰ nanoparticles at the same applied potential. The Cu nanocrystals were also catalytically stable for at least 6 h, and only 14% deactivation was observed after 12 h of CO₂ reduction. Mechanistic studies suggest that <i>n-</i>propanol could be formed through the C–C coupling of carbon monoxide and ethylene precursors. The enhanced activity of the Cu nanocrystals toward <i>n-</i>propanol formation was correlated to their surface population of defect sites

Table_1_From the West to the East: an evidence-based educational reform for modern medical students in traditional Chinese medicine learning.xlsx

IntroductionGenerally, Traditional Chinese Medicine (TCM) courses are now given to modern medicine students without proper course scheduling, resulting in poor teaching results.MethodsTo analyze the main factors affecting TCM learning, we surveyed the medical students and TCM teachers from Xiangya School of Medicine of Central South University via online questionnaires. The questionnaire comprised two parts, the students' part included the basic information, the subjective cognition in TCM, the attitude toward TCM course arrangements, and the attitude toward curriculum content and the design of TCM. The teachers' part included the basic information, the attitudes and opinions on TCM course arrangements, and suggestions and views on TCM teaching reform. The related data were collected from 187 medical students divided into two groups, namely, clinical medical students and non-clinical medical students.ResultsWe found a more positive attitude toward TCM [including “Scientific nature of TCM” (P = 0.03) and “Necessity for modern medicine students to learn TCM” (P = 0.037)] in clinical medical students compared with non-clinical medical students, clinical and non-clinical medical students tended to find TCM courses difficult, and the students prefer clinical training to be better than theoretical teaching, while the teachers believe that lecture-based education should have a more significant proportion.DiscussionHence, to optimize the current TCM teaching, we conducted education reform, including differentiated teaching, hybrid teaching, and selective teaching.</p

Results of linear regression for predictors associated with CONSORT methodological score.

<p>Note: ^¶When data on “blinding” were deleted, two predictors associated with CONSORT score (i.e., publication year and ITT analysis) remained, and their P values were 0.005 and <0.001 respectively.</p><p>Results of linear regression for predictors associated with CONSORT methodological score.</p

Flow diagram of included studies.

<p>Flow diagram of included studies.</p

Characteristics of Included Studies.

<p>*Items are reported as frequency and proportion for categorical variables and are otherwise specified for continuous variables.</p>§<p>CONSORT was published in 1996 and revised twice in 2001 and 2010, respectively; the number of RCTs in each publication year is depicted in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0113002#pone.0113002.s004" target="_blank">Appendix S4</a>.</p>¶<p>There is a significant difference between the number of words used to describe interventions and controls,as indicated by two related-samples tests (Z = −21.192, P<0.001);</p><p>IQR indicates interquartile range.</p><p>Characteristics of Included Studies.</p

Investigating the Role of Copper Oxide in Electrochemical CO₂ Reduction in Real Time

Copper oxides have been of considerable interest as electrocatalysts for CO₂ reduction (CO2R) in aqueous electrolytes. However, their role as an active catalyst in reducing the required overpotential and improving the selectivity of reaction compared with that of polycrystalline copper remains controversial. Here, we introduce the use of selected-ion flow tube mass spectrometry, in concert with chronopotentiometry, in situ Raman spectroscopy, and computational modeling, to investigate CO2R on Cu₂O nanoneedles, Cu₂O nanocrystals, and Cu₂O nanoparticles. We show experimentally that the selective formation of gaseous C₂ products (i.e., ethylene) in CO2R is preceded by the reduction of the copper oxide (Cu₂OR) surface to metallic copper. On the basis of density functional theory modeling, CO2R products are not formed as long as Cu₂O is present at the surface because Cu₂OR is kinetically and energetically more favorable than CO2R