Towards artificial photosynthesis
: heterogenized molecular complexes for CO2 electroreduction and optimization of perovskite solar cells

Student thesis: Doc typesDoctor of Sciences

Abstract

The field of artificial photosynthesis, in which solar light is the driving force for the conversion of CO2 and H2O to chemical fuels, was pioneered by the work of Fujishima and Honda in the 70s; thereafter, it has been largely dominated by research on the reduction of water into hydrogen and its oxidation into oxygen. Despite its thermodynamic and kinetic challenges, the research on solar-powered CO2 reduction devices has increased, in parallel to the development of selective and efficient catalysts.

The first objective of the present project was to obtain CO2-reducing molecular catalysts in pure and active form and to integrate these catalysts into nanostructured porous electrodes, to be used in an electrolyzer. In order to immobilize a Ni(cyclam) complex on the surface of an electrode, two new cyclam derivatives bearing a pyrene substitution were synthesized. The complexes were found to be very active in the immobilized form, with faradic efficiencies for CO production exceeding 90% and current densities up to 10 mA.cm-2 in an acetonitrile/water mixture. Furthermore, for one of the two new complexes, the hybrid electrodes maintained the selectivity for CO in water, with the highest Faradaic Efficiency (87%) obtained at -0.8 V vs. RHE and current density around 6 mA cm-2.

The second objective of this project, in collaboration with the Swiss company Solaronix, was to improve the power conversion efficiency (PCE) of fully printable carbon-based perovskite solar cells (PSCs). Different degrees of porosity were introduced into nanoparticle-based TiO2 scaffolds, using polymer nanospheres as sacrificial structure, by varying the nature of the polymer, the diameter of the nanosphere and the polymer/TiO2 weight ratio. The addition of 5 wt% of 300 nm polystyrene nanospheres allowed to obtain an optimized layer for which the PCE max reached 13.6%, thus confirming a strategy that has the potential to afford excellent PCE enhancements with minimum impact on the manufacturing process of printable monolithic carbon-based PSCs, a front runner on the market for its competitive low cost.
Date of Award25 Apr 2022
Original languageEnglish
Awarding Institution
  • University of Namur
  • Université de Paris IV-Sorbonne
SponsorsEuropean Commission
SupervisorBAO LIAN SU (Supervisor), Marc Fontecave (Supervisor), ROBERT SPORKEN (President), Luca Fusaro (Jury), Yann Garcia (Jury), Damien P. Debecker (Jury), Christel Laberty-Robert (Jury), Antoni Llobet (Jury) & Elodie Anxolabéhère (Jury)

Keywords

  • Artificial photosynthesis
  • CO2 electroreduction
  • molecular catalyst
  • Nickel cyclam
  • perovskite solar cells
  • mesoporous TiO2

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