Browsing by Author "Fernandes, T. R. C."
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- Conversion of carbon dioxide into fuel by electrochemical reduction in aqueous solventsPublication . Pardal, T.; Fernandes, T. R. C.; Machado, Ana; Rangel, C. M.he mission of Omnidea, a Portuguese SME is to perform leading edge R&D in innovative energy concepts. In collaboration with Research Institutes Omnidea is developing a technology based upon a regenerative energy storage cycle. In this cycle the recharge system converts CO2 into hydrocarbons using a renewable source of power. The discharge system produces electrical energy when hydrocarbons and oxygen from the recharge system are directly supplied to a device such as a Solid Oxide Fuel Cell (SOFC). This work focuses on the challenges involved in the task of bringing this technology closer to the market. A key feature of this technology is the use of copper which is known to have unique properties for converting CO2 electrochemically into hydrocarbons. The modification of copper electrodes with copper deposits to improve the catalytic activity and selectivity of the cathodes in the production of hydrocarbons in aqueous solvents is also described.
- Modified electrodes for electrochemical reduction of carbon dioxidePublication . Machado, Ana; Fernandes, T. R. C.; Pardal, T.; Rangel, C. M.The efforts to constrain greenhouse gas emissions and concerns over security of fossil fuels have led to increased attention for renewable energy for the past decade. Renewable energy is one of the key solutions to the actual energy challenges. Omnidea in collaboration with Research Institutes is developing a technology based upon a regenerative energy storage cycle that could be a contribution to a low-carbon energy future. In this cycle the recharge system, which is composed of an electrochemical cell, converts CO2 into fuel (hydrocarbons and hydrogen) using an external source of power (e.g. solar power). The discharge system produces electric energy when hydrocarbons and oxygen from the recharge system are directly supplied to a Solid Oxide Fuel Cell (SOFC). Currently state of the art systems for direct electrochemical reduction of CO2 exhibit low current densities and or low Faradaic efficiencies. Thus considerable research activity is still needed to develop electrodes with a performance suitable for an industrial application. This paper describes the progress to date and the work carried out with the aim of achieving this goal. It addresses particularly the modification of electrodes for electrochemical conversion of CO2 and reports voltammetric studies as a tool for screening and optimizing electrodes for CO2 conversion
- Scale-up of a system for hydrocarbon production by electrochemical reduction of CO2Publication . Fernandes, T. R. C.; Machado, Ana; Condeço, J.; Rangel, C. M.; Pardal, T.This work addresses the scaling up of a system for electrochemical reduction of CO2 to produce hydrocarbons that can be used as fuel for a regenerative energy storage cycle. Challenges involved in such a task are mentioned. Scalingup results of a system based on electrodes of high surface area with modified copper deposits are described. Current densities around 100 mA/cm2 were obtained. This corresponds to the current density threshold that enables technological applications. At potentials as negative as -1.6 V it was observed that CO2 reduction still dominated over hydrogen evolution reaction.
- Structural features of electrodeposited copper electrodes for CO2 conversionPublication . Machado, Ana; Fernandes, T. R. C.; Pardal, T.; Rangel, C. M.Direct electrochemical reduction of CO2 is a process that could contribute to the reduction of the emission of greenhouse gases by using CO2 as a raw material for fuel production. This paper focuses on voltammetric studies of functionalized electrodes for the electrochemical conversion of CO2 and reports on its use as a tool for electrode screening and optimization. Nickel substrates modified with copper and ruthenium/copper electrodeposits were studied. Voltammetric experiments indicate that CO2 electroreduction follows a nickel type mechanism in which this electrochemical reaction occurs simultaneously and in competition with hydrogen evolution. A significant inhibition of hydrogen evolution reaction is observed in nickel modified electrodes. Inhibition characteristics and the onset of carbon dioxide conversion are dependent of the type of electrode functionalization. Voltammetry is thus a powerful tool to evaluate electrode modifications and for tuning electrodes for an optimized electrocatalytic performance.