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Here we report on the most prominent factors influencing the performance of a Cu-based CO2 electrolyzer operating at high currents. Using a flow-electrolyzer design where CO2 gas feed passes directly through the electrode interacting with the Cu catalyst layer, we observed that the selectivity of the electrochemical CO2 reduction in (bulk) pH neutral media can greatly be influenced by adjusting the structure of the electrode. In this, the variations in catalyst loading and ionomer content can profoundly affect the selectivity of CO2RR. We explore the hypothesis that this originates from the overall mass transport variations within the porous catalytic layer of the gas diffusion electrode. As further evidence for this, apart from the CO2 electrolysis results, we propose a special method to benchmark the reactant mass transport in flow-cells using oxygen reduction reaction (ORR) limiting current measurements. Our analysis suggests that a restriction of mass transport is highly desirable due to its connection to a local alkalization and corresponding suppression of pH-dependent reaction products, given the absence of local CO2 concentration limitations. We further show how the electrode structure can be used to push the observed catalytic CO2 reduction selectivity either towards C1 or C2+ products, dependent on the ionomer content and catalyst loading in a cathodic current range of 50 to 700 mA cm−2. Measurements at various KHCO3 electrolyte concentrations agree with the notion of the local pH dictating the overall selectivity and point towards the presence of pronounced concentration gradients within the system. Overall, our work suggests that the differences in electrocatalytic CO2 reduction selectivity at high currents (in a range of pH neutral buffering electrolytes) largely originate from the local concentration gradients defined by the initial catalyst ink formulation and architecture of the catalytic layer, both of which represent a powerful tool for optimization in the production of selected value-added products.

Correction for ‘Up-scalable emerging energy conversion technologies enabled by 2D materials: from miniature power harvesters towards grid-connected energy systems’ by Konstantinos Rogdakis et al., Energy Environ. Sci., 2021, DOI: 10.1039/d0ee04013d.

Abstract Sodium-cooled Fast Reactors and Lead-cooled Fast Reactors have been selected by the Sustainable Nuclear Energy Technology Platform as technologies that can meet future European energy needs. To achieve the requested level of safety for these reactor technologies and to minimize the increase in the costs due to additional safety measures, accurate and reliable nuclear data are necessary. The objective of this work has been to analyse and improve the nuclear data required for the development, safety assessment and licensing of SFRs and LFRs, reducing the uncertainties in the reactor integral responses due to the uncertainties in nuclear data, in order to reach the target accuracies defined by researchers, industry and regulators. To that end, target accuracy and data assimilation analyses have been performed to identify nuclear data weaknesses and to reduce the uncertainties of integral safety-related parameters due to neutron induced nuclear data. As a result of this work, nuclear data needs for advanced SFRs and LFRs have been identified, improvements of existing nuclear data libraries have been suggested, nuclear data have been adjusted and uncertainties in reactor integral parameters have been reduced, meeting target accuracies after adjustment.

The annual report of the Institute for Nuclear and Energy Technologies of KIT summarizes its research activities and provides some highlights of each working group, like thermal-hydraulic analyses for fusion reactors, accident analyses for light water reactors, and research on innovative energy technologies: liquid metal technologies for energy conversion, hydrogen technologies and geothermal power plants. The institute has been engaged in education and training in energy technologies.

This paper reports on the ion fluxes at the interfaces of various porous carbon electrodes/aqueous solutions of alkali metal cations (Na+, K+ and Rb+) and iodide anions, monitored by an electrochemical quartz crystal microbalance (EQCM). Different electrode material compositions as well as various electrolyte concentrations have also been considered. By tracking the ions during electrochemical polarization, we aimed to identify the reasons for the fading capacitor performance that occurs during long-term operation. The mass change profile suggests that hydroxide anions are responsible for counterbalancing the charge stored on the negative electrode. Furthermore, we found that iodide-based species are physically adsorbed on the carbon surface immediately after the electrodes come into contact with the electrolyte, regardless of the textural properties of the activated carbon used or electrode composition. Apart from the qualitative description, the mass change profiles allow the sequence of pore occupation to be determined. Additionally, the solvation numbers for alkali metals (Na+, K+ and Rb+) and hydroxide-based species have been determined. It is claimed that the solvation number is strongly affected by the electrolyte composition. Apparently, the concentration of water molecules available in the electrolyte cannot be neglected. The outcome of this research has fundamental and application context.

Abstract The effects of a short plasma density scale length on laser-driven proton acceleration from foil targets is investigated by heating and driving expansion of a large area of the target rear surface. The maximum proton energy, proton flux and the divergence of the proton beam are all measured to decrease with increasing extent of the plasma expansion. Even for a small plasma scale length of the order of the laser wavelength (∼1 µm), a significant effect on the generated proton beam is evident; a substantial decrease in the number of protons over a wide spectral range is measured. A combination of radiation-hydrodynamic and particle-in-cell simulations provide insight into the underlying physics. The results provide new understanding of the importance of even a small plasma density gradient, with implications for applications that require efficient laser energy conversion to ions, such as proton-driven fast-ignition of compressed fusion fuel.

The integration of carbon capture and CO2 utilization could be a promising solution to the crisis of global warming. By integrating calcium-looping (CaL) and the reverse-water-gas-shift (RWGS) reaction, a high-temperature CO2 capture and in situ conversion technology is successfully realized in one fixed-bed column at the same operating temperature of 650 °C. Inspired by the heterojunction photocatalytic mechanism, the heterojunction-redox catalysis strategy is proposed for the first time by doping the bimetallic Fe3+/Fe2+ and Co3+/Co2+ redox couples into a hierarchical porous CaO/MgO composite. The presence of different valence states of doped Fe and Co oxides not only provides extra oxygen vacancies to facilitate CO2 adsorption, and hence adsorption enhanced conversion (AEC), but also significantly lowers the electric potential difference of Fe3+/Fe2+ through the newly formed Fermi level in Fe5Co5Mg10CaO, which makes electron spillover easier to improve the catalytic activity in the RWGS reaction for CO2 conversion. More importantly, with the high-temperature refractory MgO and the highly disperse Fe and Co oxides in Fe5Co5Mg10CaO, the problem of CaO sintering is successfully solved. An excellent and stable high-temperature CO2 capture capacity of 9.0–9.2 mmol g−1, an in situ CO2 conversion effeciency near 90% and a CO selectivity close to 100% are achieved in the integrated CaL/RWGS process. In addition, experimental and simulation scale-up studies further demonstrate its pratical scalability. Economic evaluation reveals that the integrated CaL/RWGS technology is much more cost-effective than the individual CaL and RWGS processes. Therefore, the heterojunction-redox strategy provides a unique way to design bifunctional adsorbent/catalyst materials. The integrated CaL/RWGS process could be a promising technology for CO2 capture and utilization.