The scaling-up of electrochemical CO2 reduction requires circumventing the CO2 loss as carbonates under alkaline conditions. Zero-gap cell configurations with a reverse-bias bipolar membrane (BPM) ...represent a possible solution, but the catalyst layer in direct contact with the acidic environment of a BPM usually leads to H2 evolution dominating. Here we show that using acid-tolerant Ni molecular electrocatalysts selective (>60%) CO2 reduction can be achieved in a zero-gap BPM device using a pure water and CO2 feed. At a higher current density (100 mA cm–2), CO selectivity decreases, but was still >30%, due to reversible product inhibition. This study demonstrates the importance of developing acid-tolerant catalysts for use in large-scale CO2 reduction devices.
Cu–In metallic hybrid is a promising non-noble catalyst for selective electrochemical CO2 reduction (eCO2R) to CO, but the lack of direct assembly with a gas diffusion electrode (GDE) limits the ...further development of eCO2R to CO with both high Faradaic efficiency (FE) and high current density. In this study, an in situ electrochemical spontaneous precipitation (ESP) method was applied for the first time to prepare GDE-combined Cu–In electrocatalysts. The optimum Cu–In catalyst consists of a nanoscale “core–shell” structure of polycrystalline Cu x O covered by the amorphous In(OH)3 interface. Higher than 90% FE of CO production has been achieved. With the synergy of a GDE flow cell and 1 M KOH catholyte, a current density of ∼200 mA cm–2 was reached at −1.17 V (reversible hydrogen electrode), which enabled a CO yield efficiency record of 3.05 mg min–1(CO2/15 mL min–1 with a 2 cm2 electrode). The ratios between CO and H2 produced can be effectively modulated via fine-tuning ESP conditions demonstrating possibility of generating CO or syngas with tuneable ratios. The present study provides a simple approach for constructing novel catalytic interfaces with dual active centers for eCO2R and other emerging electrochemical catalysis research.
Microbial fuel cells (MFCs), which convert organic waste to electricity, could be used to make the wastewater infrastructure more energy efficient and sustainable. However, platinum and other ...non-platinum chemical catalysts used for the oxygen reduction reaction (ORR) at the cathode of MFCs are unsustainable due to their high cost and long-term degradation. Aerobic biocathodes, which use microorganisms as the biocatalysts for cathode ORR, are a good alternative to chemical catalysts. In the current work, high-performing aerobic biocathodes with an onset potential for the ORR of +0.4 V vs. Ag/AgCl were enriched from activated sludge in electrochemical half-cells poised at −0.1 and + 0.2 V vs. Ag/AgCl. Gammaproteobacteria, distantly related to any known cultivated gammaproteobacterial lineage, were identified as dominant in these working electrode biofilms (23.3–44.3% of reads in 16S rRNA gene Ion Torrent libraries), and were in very low abundance in non-polarised control working electrode biofilms (0.5–0.7%). These Gammaproteobacteria were therefore most likely responsible for the high activity of biologically catalysed ORR. In MFC tests, a high-performing aerobic biocathode increased peak power 9-fold from 7 to 62 μW cm−2 in comparison to an unmodified carbon cathode, which was similar to peak power with a platinum-doped cathode at 70 μW cm−2.
•Uncultured Gammaproteobacteria dominate in high-performing aerobic biocathodes.•Microbial fuel cell biocathode performance comparable to a platinized cathode.•Oxygen reduction catalysis linked to a bacterial electron transport chain.•Additional electron transport pathways may be present at different poised-potential.
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•Low cost Sn-Pb-Sb alloy converts CO2 efficiently to formate with 91% Faradaic efficiency.•Sb in Sn rich alloy improved the conductivity and enhanced the eCO2R activity.•Enhanced ...eCO2R activity is attributed to the synergistic metal/metal oxide effects.
Oxide-derived (OD) Sn and Sn−Pb−Sb composite electrocatalysts were prepared by electrochemical oxidation treatment at various potentials for electrochemical reduction of CO2 (eCO2R) for formate (HCOO−) production. The morphology, elemental mapping, phase identification, surface characteristics and electrochemical performance of the electrocatalysts were probed systematically. The surface of OD-Sn and OD-Sn-Pb-Sb shows polycrystalline electrodes with porous morphology and XPS results confirm the formation of composite metal/metal oxide surface related to Sn, Pb and Sb. The EDX mapping analysis shows two distant regions of Pb and Sn rich areas in the alloy. The electrochemical results demonstrate that pristine Sn electrodes show higher CO2 Faradaic Efficiency (FE) to formate compared to pristine Sn-Pb-Sb alloy electrode (80% vs. 66%) at −1.4 V vs. RHE. Upon oxidation treatment of pristine Sn at 4 V, the FEHCOO− improves to 84% at the expense of decreased current density. On the contrary, upon oxidation treatment of Sn-Pb-Sb alloy at 5 V, the FEHCOO− improved remarkably from 68% to 91% without any reduction in current density. The improved eCO2R performance of OD-Sn and OD-Sn-Pb-Sb electrodes relative to their pristine electrodes could be attributed to the presence of composite metal/metal oxide structure which leads to local geometric and electronic structural changes.
Despite some success with microbial fuel cells and microbial electrolysis cells in recovering resources from wastes, challenges with their scale and yield need to be resolved. Waste streams from ...biorefineries e.g. bioethanol and biodiesel plants and wastewaters are plausible substrates for microbial electrosynthesis (MES). MES integration can help biorefineries achieving the full polygeneration potentials, i.e. recovery of metals turning apparently pollutants from biorefineries into resources, production of biofuels and chemicals from reuse of CO2 and clean water. Symbiotic integration between the two systems can attain an economic and environmental upside of the overall system. We envision that electrochemical technologies and waste biorefineries can be integrated for increased efficiency and competitiveness with stillage released from the latter process used in the former as feedstock and energy resource recovered from the former used in the latter. Such symbiotic integration can avoid loss of material and energy from waste streams, thereby increasing the overall efficiency, economics and environmental performance that would serve towards delivering the common goals from both the systems. We present an insightful overview of the sources of organic wastes from biorefineries for integration with MES, anodic and cathodic substrates and biocatalysts. In addition, a generic and effective reaction and thermodynamic modelling framework for the MES has been given for the first time. The model is able to predict multi-component physico-chemical behaviour, technical feasibility and best configuration and conditions of the MES for resource recovery from waste streams.
Pulsed electrolysis can significantly improve carbon dioxide reduction on metal electrodes, but the effect of short (millisecond to seconds) voltage steps on molecular electrocatalysts is largely ...unstudied. In this work, we investigate the effect pulse electrolysis has on the selectivity and stability of the homogeneous electrocatalyst Ni(cyclam)2+ at a carbon electrode. By tuning the potential and pulse duration, we achieve a significant improvement in CO Faradaic efficiencies (85%) after 3 h, double that of the system under potentiostatic conditions. The improved activity is due to in situ catalyst regeneration from an intermediate that occurs as part of the catalyst’s degradation pathway. This study demonstrates the wider opportunity to apply pulsed electrolysis to molecular electrocatalysts to control activity and improve selectivity.
Compelling evidence supports vascular contributions to cognitive impairment and dementia (VCID) including Alzheimer's disease (AD), but the underlying pathogenic mechanisms and treatments are not ...fully understood. Cis P-tau is an early driver of neurodegeneration resulting from traumatic brain injury, but its role in VCID remains unclear. Here, we found robust cis P-tau despite no tau tangles in patients with VCID and in mice modeling key aspects of clinical VCID, likely because of the inhibition of its isomerase Pin1 by DAPK1. Elimination of cis P-tau in VCID mice using cis-targeted immunotherapy, brain-specific Pin1 overexpression, or DAPK1 knockout effectively rescues VCID-like neurodegeneration and cognitive impairment in executive function. Cis mAb also prevents and ameliorates progression of AD-like neurodegeneration and memory loss in mice. Furthermore, single-cell RNA sequencing revealed that young VCID mice display diverse cortical cell type-specific transcriptomic changes resembling old patients with AD, and the vast majority of these global changes were recovered by cis-targeted immunotherapy. Moreover, purified soluble cis P-tau was sufficient to induce progressive neurodegeneration and brain dysfunction by causing axonopathy and conserved transcriptomic signature found in VCID mice and patients with AD with early pathology. Thus, cis P-tau might play a major role in mediating VCID and AD, and antibody targeting it may be useful for early diagnosis, prevention, and treatment of cognitive impairment and dementia after neurovascular insults and in AD.
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•O2 plasma was used for introducing oxygen-containing groups on rGO surface.•Exposure time has an influence on the amount and type of functional groups.•Porosity and surface area ...increased after plasma treatment.•Electrocatalytic current density was doubled for BOD-modified rGO-10 min electrode.•O2 plasma-treated rGO surface served as suitable platform for BOD adsorption.
We report an easily controllable, eco-friendly method for tailoring the properties of reduced graphene oxide (rGO) by means of oxygen plasma. The effect of oxygen plasma treatment time (1, 5 and 10 min) on the surface properties of rGO was evaluated. Physicochemical characterization using microscopic, spectroscopic and thermal techniques was performed. The results revealed that different oxygen-containing groups (e.g. carboxyl, hydroxyl) were introduced on the rGO surface enhancing its wettability. Furthermore, upon longer treatment time, other functionalities were created (e.g. quinones, lactones). Moreover, external surface of rGO was partially etched resulting in an increase of the material surface area and porosity. Finally, the oxygen plasma-treated rGO electrodes with bilirubin oxidase were tested for oxygen reduction reaction. The study showed that rGO treated for 10 min exhibited twofold higher current density than untreated rGO. The oxygen plasma treatment may improve the enzyme adsorption on rGO electrodes by introduction of oxygen moieties and increasing the porosity.
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•Gas diffusion electrodes enhanced the selectivity of carbonaceous products.•High hydroxide concentrations led to faster kinetics and lower activation energy.•High alkalinity ...stabilized oxygen surface group for oxide derived Cu catalysts.•C2 Faradic Efficiency of 40%, maximum current density of −234 mA cm−2 achieved.
This study highlights the importance of CO2 supply method and impact of electrolyte alkalinity in aqueous electrochemical CO2 reduction using CuxO catalyst. Two different CO2 supply methods using a two-chamber (2C) cell with CO2 purging into catholyte and a CO2 gas diffusion electrode (GDE) cell were compared. Faradaic efficiency (FE) of carbonaceous products in GDE cell was more than 3-folds higher than the 2C cell due to improved CO2 mass transfer. From the investigation of alkaline catholyte in GDE cell, the higher catholyte alkalinity led to higher current density and higher FE of carbonaceous products with a better selectivity of C2 (ethanol and ethylene). The reason lies in the OH groups around catalyst surface which improve the reaction kinetics and moreover stabilize the catalyst surface oxygen during the reduction process. With the potential of −1.17 V (RHE) in 2.0 M KOH, C2 FE of 40% and current density of −234 mA cm−2 were achieved. The production rate of ethylene and ethanol was respectively 0.105 mg min−1 and 0.035 mg min−1 on 2 cm2 electrode with CO2 flow rate 15 ml min−1, which are promising for further development and scale-up.
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