RESUMO
Currently, the most promising amine absorption system for CO2 capture still faces the challenges of heavy steam consumption and a high energy penalty. Thus, a new thermal-electrochemical co-driven system (TECS) for CO2 capture was developed to resolve these problems. In the TECS, unknown electrochemical behaviors are quite essential to assess the CO2 capture performance. Electrochemical experiments were designed using response surface methodology (RSM) to identify electrochemical effects. The results show that the cathode process is slow and difficult, which is the main limitation in improving the performance of the TECS. Forced convection is necessary to improve the diffusion-controlled process and accelerate desorption. Four factors (Cu(ii) molality, CO2 loading, temperature, KNO3 molality) play an auxo-action role in determining anode and cathode reaction rates. A regression model is developed based on the experimental data, and optimum operating conditions are obtained. Regeneration energy consumption reaches about 1.3 GJ per t CO2, a decline of up to 70% compared with the traditional process. In addition, preliminary CO2 desorption experiments suggest that the mass transfer ascribed to the electrochemical process accounts for over 50% of the overall mass transfer coefficient in the CO2 desorption process.
RESUMO
We report a new strategy to improve the reactivity and durability of a membrane electrode assembly (MEA)-type electrolyzer for CO2 electrolysis to CO by modifying the silver catalyst layer with urea. Our experimental and theoretical results show that mixing urea with the silver catalyst can promote electrochemical CO2 reduction (CO2R), relieve limitations of alkali cation transport from the anolyte, and mitigate salt precipitation in the gas diffusion electrode in long-term stability tests. In a 10 mM KHCO3 anolyte, the urea-modified Ag catalyst achieved CO selectivity 1.3 times better with energy efficiency 2.8-fold better than an untreated Ag catalyst, and operated stably at 100 mA cm-2 with a faradaic efficiency for CO above 85% for 200 h. Our work provides an alternative approach to fabricating catalyst interfaces in MEAs by modifying the catalyst structure and the local reaction environment for critical electrochemical applications such as CO2 electrolysis and fuel cells.
RESUMO
Interactions of electrolyte ions at electrocatalyst surfaces influence the selectivity of electrochemical CO2 reduction (CO2 R) to chemical feedstocks like CO. We investigated the effects of anion type in aqueous choline halide solutions (ChCl, ChBr, and ChI) on the selectivity of CO2 R to CO over an Ag foil cathode. Using an H-type cell, we observed that halide-specific adsorption at the Ag surface limits CO faradaic efficiency (FECO ) at potentials more positive than -1.0â
V vs. reversible hydrogen electrode (RHE). At these conditions, FECO increased from I-
RESUMO
Achieving high product selectivities is one challenge that limits viability of electrochemical CO2 reduction (CO2 R) to chemical feedstocks. Here, it was demonstrated how interactions between Ag foil cathodes and reline (choline chloride + urea) led to highly selective CO2 R to CO with a faradaic efficiency of (96±8) % in 50â wt % aqueous reline at -0.884â V vs. the reversible hydrogen electrode (RHE), which is a 1.5-fold improvement over CO2 R in KHCO3 . In reline the Ag foil was roughened by (i)â dissolution of oxide layers followed by (ii)â electrodeposition of Ag nanoparticles back on cathode. This surface restructuring exposed low-coordinated Ag atoms, and subsequent adsorption of choline ions and urea at the catalyst surface limited proton availability in the double layer and stabilized key intermediates such as *COOH. These approaches could potentially be extended to other electrocatalytic metals and lower-viscosity deep eutectic solvents to achieve higher-current-density CO2 R in continuous-flow cell electrolyzers.
RESUMO
Invited for this month's cover is the group of Tom Rufford at the University of Queensland. The image shows how choline chloride and urea in a reline solution interact with the surface of a silver cathode to enhance the selectivity of electrochemical CO2 reduction to CO. The Full Paper itself is available at 10.1002/cssc.201902433.
RESUMO
Leaf shape, including leaf size, leaf dissection index (LDI), and venation distribution, strongly impacts leaf physiology and the forces of momentum exerted on leaves or the canopy under windy conditions. Yet, little has been known about how leaf shape affects the morphological response of trees to wind load. We studied eight Quercus species, with different leaf shapes, to determine the morphological response to simulated wind load. Quercus trees with long elliptical leaves, were significantly affected by wind load (P< 0.05), as indicted by smaller specific leaf area (SLA), stem base diameter and stem height under windy conditions when compared to the control. The Quercus trees with leaves characterized by lanceolate or sinuous edges, showed positive morphological responses to wind load, such as bigger leaf thickness, larger stem diameter, allocation to root biomass, and smaller stem height (P< 0.05). These morphological responses to wind can reduce drag and increase the mechanical strength of the tree. Leaf dissection index (LDI), an important index of leaf shape, was correlated with morphological response to wind load (P< 0.05), including differences in SLA, in stem base diameter and in allocation to root biomass. These results suggest that trees with higher LDI, such as those with more and/or deeper lobes, are better adapted to wind load.