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PhD defense
Electrode-confined molecular hybrid catalysts are a promising strategy to efficiently and selectively convert CO2 into useful chemicals for energy storage with promising perspectives of integration into industrial relevant CO2 reduction electrolytic cells. Within this work, the development of a novel molecular hybrid catalyst for selective CO2-to-CO reduction was described. This Co-based tetraazamacrocyclic complex could be integrated through non-covalent interaction to a carbon nanotube-based electrode. Electrochemical characterisation in fully aqueous media of the modified molecular electrode showcase the impact of the surface microenvironment on the redox properties of the Co complex. The molecular Co-based cathode demonstrates effective CO2-to-CO reduction in fully aqueous media, allowing maximum turnover numbers for CO production of up to 3 × 105 after 1 h of constant electrolysis at low overpotential ( = 450 mV) with excellent faradic efficiencies for CO of (>95%). Post operando measurements using electrochemical techniques, inductively coupled plasma, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy analysis of the molecular films demonstrated the retained molecular nature of the hybrid catalyst after electrolysis. Along with mass spectrometry measurements, these techniques allowed gaining insights into the deactivation mechanism of the confined molecular catalyst. Integration of the Co-based molecular cathode into a zero-gap electrolyser cell gave rise to reasonable current densities of 70 mA cm−2 with excellent CO faradaic efficiencies of 98% at a cell voltage of 2.9 V under slightly alkaline conditions. Additionally, excellent selectivity of 98% for CO could be reach at very low cell voltage. These metrics reveal the promising CO2-to-CO reduction activity of this Co-based molecular cathode as a new alternative of molecular cathodes in fully aqueous media, as well as once integrated into a zero-gap electrolyser.
Supervision: Vincent ARTERO (DIRECTEUR DE RECHERCHE CEA centre de Grenoble)
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CEA is a French government-funded technological research organisation in four main areas: low-carbon energies, defense and security, information technologies and health technologies. A prominent player in the European Research Area, it is involved in setting up collaborative projects with many partners around the world.