Electrochemical CO2 Reduction - A Critical View on Fundamentals, Materials and Applications

The electrochemical reduction of CO2 has been extensively studied over the past decades. Nevertheless, this topic has been tackled so far only by using a very fundamental approach and mostly by trying to improve kinetics and selectivities toward specific products in half-cell configurations and liquid-based electrolytes. The main drawback of this approach is that, due to the low solubility of CO2 in water, the maximum CO2 reduction current which could be drawn falls in the range of 0.01–0.02 A cm–2. This is at least an order of magnitude lower current density than the requirement to make CO2-electrolysis a technically and economically feasible option for transformation of CO2 into chemical feedstock or fuel thereby closing the CO2 cycle. This work attempts to give a short overview on the status of electrochemical CO2 reduction with respect to challenges at the electrolysis cell as well as at the catalyst level. We will critically discuss possible pathways to increase both operating current density and conversion efficiency in order to close the gap with established energy conversion technologies

Atopic dermatitis and vitamin D: facts and controversies

Patients with atopic dermatitis have genetically determined risk factors that affect the barrier function of the skin and immune responses that interact with environmental factors. Clinically, this results in an intensely pruriginous and inflamed skin that allows the penetration of irritants and allergens and predisposes patients to colonization and infection by microorganisms. Among the various etiological factors responsible for the increased prevalence of atopic diseases over the past few decades, the role of vitamin D has been emphasized. As the pathogenesis of AD involves a complex interplay of epidermal barrier dysfunction and dysregulated immune response, and vitamin D is involved in both processes, it is reasonable to expect that vitamin D's status could be associated with atopic dermatitis' risk or severity. Such association is suggested by epidemiological and experimental data. in this review, we will discuss the evidence for and against this controversial relationship, emphasizing the possible etiopathogenic mechanisms involved.Univ Brasilia UNB, Brasilia, DF, BrazilFed Dist Hlth State Dept SES DF, Brasilia, DF, BrazilUniv Brasilia HUB UNB, Brasilia Univ Hosp, Brasilia, DF, BrazilSão Paulo Fed Univ UNIFESP, Brasilia, DF, BrazilSão Paulo Fed Univ UNIFESP, Brasilia, DF, BrazilWeb of Scienc

Electrochemical reactivity in nanoscale domains: O-2 reduction on a fullerene modified gold surface

Fullerene is strongly adsorbed on both single crystal and polycrystalline gold surfaces and its specific adsorption resulted in the formation of high coverage large hexagonal rafts with strong interactions between the adsorbed fullerene molecules and the Au substrate. The oxygen reduction reaction (ORR) was investigated on these surfaces to determine their influence on the reduction mechanism. Oxygen reduction did not take place on the fullerene overlayer but proceeded on the sub-nanometer sized exposed pockets of the underlying Au substrate. Reduction at these confined sites produces hydrogen peroxide selectively. This effect is ascribed to the blocking action, or so-called "third body effect\u27\u27, of the adsorbed fullerene molecules, which do not display electrocatalytic properties for oxygen reduction

Probing the chemical state of tin oxide NP catalysts during CO₂ electroreduction: A complementary operando approach

In this paper we combine two operando methods, Raman spectroscopy and X-ray absorption spectroscopy (XAS), in order to probe reduced graphene-oxide supported tinIV oxide nanoparticles (SnO2NPs@rGO) as they are being used to catalyse CO2 electroreduction. To achieve high reaction rates it is necessary to apply sufficiently cathodic electrode potentials. Under such conditions, however, not only CO2 is reduced electrochemically, but also the catalyst particles may be transformed from the initial SnIV state to SnII or, in an extreme case, to metallic Sn. While SnII species still favour CO2 electroreduction, yielding formate as a primary product, on metallic Sn CO2 reduction is disfavoured with respect to the competing hydrogen evolution reaction (HER). We show that operando XAS, a robust technique yielding information averaged over a large surface area and a relatively large thickness of the catalyst layer, is a very expedient method able to detect the reduction of SnO2NPs@rGO to metallic Sn. XAS can thus be used to establish an optimum potential for the electroreduction in practical electrolysing cells. It takes, however, a complementary method offered by operando Raman spectroscopy, having greater sensitivity at the catalyst/electrolyte solution interface, to probe reduction intermediates such as the SnII state, which remain undetectable for ex situ methods. As it is shown in the paper, Raman spectroscopy may also find further use when investigating the recovery of catalyst particles following exposure to extreme reducing conditions