The main objective of the PEC laboratory is to convert CO2 into methanol using energy that is not produced from fossil fuels. Among the available technologies, photoelectrochemical (PEC) reduction is an innovative method that converts CO2 removed from effluent gases into value-added chemicals and fuels, such as hydrogen, carbon monoxide, hydrocarbons, and oxygenates. Moreover, the integration of renewable energy could make this technology a potential candidate for a use environmentally sustainable of CO2 that can support storage, both to reduce total costs and the distance between emission sources and storage sites.
The PEC Lab facility has been conceived in different sections:
• a photoanode-driven PEC cell that consists of a photo-anode half-cell (WO3-TiO2 nanotubular structures), a cathode half-cell (copper-based electrodes with different substrates, such as BDD or TiO2 nanotubes) and a protonic membrane (Nafion);
• a solar simulator (LOT Quantum Design), a potentiostat/galvanostat (Autolab PGSTAT204), a micro gas chromatograph (Agilent R3000) for the analysis of the gas phase and a gas chromatograph (Agilent GC7890A) with a mass spectrometer (Agilent 5977A MSD) to analyse the liquid phase.
• two EL-Bronkhorst flow meters to set the gas feeding (CO2 and N2).
The simplified process can be summarized as follows: 1) the light crosses the quartz window and reaches the photoanode, where photo-generated electrons and hole pairs are generated and O2 evolves; 2) the protons pass through the protonic membrane, while electrons are collected and reach the cathode through an external wire; 3) the protons react with CO2 in presence of electrons on the electrocatalyst to produce methanol. The physical separation of the two reactions of water oxidation and CO2 reduction in a photoanode and electrocathode respectively is necessary to increase the efficiency of the process and limit charge recombination.
The PEC Lab allows the adoption of different electrochemical techniques, both in continuous and alternating current, in order to gather information on the process using sintered electrodes. In particular, cyclic voltammetry, linear sweep voltammetry and electrochemical impedance spectroscopy (EIS) can be performed. The experimental results allow the implementation of a mathematical model of the process, in order to quantify the effect of operating parameters on the reaction and its products. The results can make it possible to optimize both cell configuration and potential or the applied values.
The gas chromatograph of the facility (Agilent GC7890A) is equipped with a Flex Series Robotic Sampling Platform that provides SPME, Headspace and Liquid Injection to analyse liquid products in different media.
The PEC Lab can be easily integrated with facilities that conduct research on technologies for CO2 capture (such as those already present at the Sotacarbo Research Centre).
The facility is located in a laboratory of the Sotacarbo Research Centre. All the services, instruments and the other facilities of Sotacarbo are therefore available in support of the research activities performed at the PEC Lab.