Syngas production by electrocatalytic reduction of CO2 by using Ag-decorated TiO2 nanotubes
Simelys Hernàndez a, M.Amin Farkhondehfal b, Matteo Rattalino a, Michiel Makkee c, Andrea Lamberti a, Angelica Chiodoni b, Katarzyna Bejtka b, Adriano Sacco b, Fabrizio Pirri a, Nunzio Russo a
a Department of applied science and technology (DISAT), Politecnico di Torino, Duca degli Abruzzi, 24, 10129, Turin, Italy
b Center for Sustainable Future Technologies, IIT@Polito, Istituto Italiano di Tecnologia, Via Livorno, 60, 10144, Turin, Italy.
c Catalysis Engineering, Dept. of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology, Delft, the Netherlands
nanoGe Fall Meeting
Proceedings of nanoGe Fall Meeting19 (NGFM19)
#SolCat19. (Photo)electrocatalysis for sustainable carbon utilization: mechanisms, methods, and reactor development
Berlin, Germany, 2019 November 3rd - 8th
Organizers: Matthew Mayer and Ludmilla Steier
Poster, Simelys Hernàndez, 307
Publication date: 16th July 2019

The CO2 electrochemical (EC) reduction is considered a promising technology for the storage and reutilization of CO2 from both economic and environmental points of view. The competitive H2 evolution side-reaction in all aqueous-electrolyte-based CO2 EC reduction proccesses, can be exploited in a competitive approach for the production of syngas with different CO/H2 ratios. Syngas a mixture for which there are well-established options for further processing to obtain more reduced products, such as alcohols and hydrocarbons (e.g. via heterogeneous Fischer-Tropsch catalysis) [1]. In this work, TiO2 nanotubes (NTs) were grown by anodic oxidation of Ti foils and were then decorated with Ag nanoparticles (NPs) deposited by sputtering with a low loading (<20 wt%) [2]. Due to their quasi 1D structure, the TiO2 NTs provides a higher surface area and better electron transport properties than other Ti-based substrates, like Ti foil and TiO2 NPs. These results were confirmed by electrochemical techniques (CV, EIS, electrochemical active surface area) and chemical-physical analysis (FESEM, TEM, EDS). Additionally, the TiO2 NTs play a role in enhancing the stability of the CO2·- intermediate thanks to the titania (TiIV/TiIII) redox behaviour, leading to an improvement of the CO production in the Ag/TiO2 NTs electrodes. The best Ag NPs/TiO2 NTs sample outperform Ag-decorated TiO2 NPs (see Fig. 1) [2], achieving a molar ratio of CO/H2 of 1:2 which is suitable as feedstock for methanol production. A noteworthy current density of -65 mA/cm2 was achieved for the EC CO2 reduction at -1.6V vs SHE, which can be considered high with respect to the experiments carried out with bulk noble metal-based electrodes. This work opens new doors for using nanostructures of metal oxides like titania as a support for electrocatalyst in CO2 reduction. However, the stability of the electrocatalyst and production rate of syngas are still a challenge that needs to be resolved to achieve an industrial relevant scale.

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