Emmanuel Skupien

Enmanuel

Julianalaan 136, 2628 BL Delft
ChemE 0.481
Tel: *31 (0)15-2786300
   

E.Skupien@tudelft.nl 



Electrocatalytic Reduction of CO2

The recent United Nations Climate Change Conference (Copenhagen, December 2009) has further raised the urgency in decreasing carbon dioxide emissions and accelerating the introduction of renewables in the energy pool [1]. However, carbon dioxide emissions are difficult to avoid, due to the costs involved in its treatment as disposal. Tremendous efforts have been allocated to prevent the accumulation of atmospheric CO2, such as removal or sequestration. However, CO2 conversion is the preferred solution because of unknown ecological impacts associated with storage or sequestration [2]. In particular, transformation of CO2 into useful substances, such as transportable fuels [3], is an attractive option that leads to the establishment of closed energy and carbon cycles. The feasibility of this process could enable the application of artificial photosynthesis at a large scale. Considering these points, CO2 is potentially a means for energy storage and conversion rather than being a waste with costs of disposal [4]. 

Figure 1E

Figure 1: Schematic representation of artificial photosynthesis involving a photovoltaic solar cell coupled with an electrolytic cell for CO2 electrocatalytic reduction to hydrocarbons

Carbon dioxide electrocatalytic reduction to hydrocarbons such as ethylene has been proven possible in the late 80’s [5], but the conversion to carbon monoxide and formic acid was already known before in the electrochemical field. However, a proper control over the selectivity to certain hydrocarbons, as well as a complete understanding of the fundamental parameters leading to such selectivity is not yet established. The production rates also remain very low, mainly due to the hydrogen evolution reaction that is thermodynamically favored at the working potential and is difficult to avoid. Thus protons remain the major species covering the electrode surface, leading to high rates of molecular hydrogen produced requiring more energy than the energy stored. Certain types of porous electrodes called gas diffusion electrodes can be used as a support to immobilize nanoparticle catalysts, bringing together the fields of electrochemistry and catalysis.  If the nanoparticles used possess a high activity, such as colloidal nanoparticles [6], there is then the possibility to enhance the efficiency of CO2 electrocatalytic reduction.

Figure 2E

Figure 2: Schematic illustration of a gas diffusion electrode for CO2 electrocatalytic reduction.

Objectives

  • Application of well-defined catalyst nanoparticles immobilized on a nanostructured gas diffusion electrode for an enhanced and controlled productivity and selectivity in the electrocatalytic reduction of carbon dioxide to hydrocarbons.
  • Optimization of the gas diffusion electrode electrolytic cell. Investigation of the influence of transport phenomena on efficiency and selectivity.
  • Immobilization of capping agent-stabilized nanoparticles by grafting, comparison with more traditional immobilization methods.
  • Investigation of the effects of temperature treatments on the catalytic activity of the capping agent-stabilized nanoparticle catalyst.
  • Research of the minimum particle size (if there is) below which catalytic activity and/or selectivity towards long chain hydrocarbons is affected (ensemble effect).
  • Determination of the surface crystallographic sites of the nanoparticle catalysts.
  • Determination of the surface oxidic species on the nanoparticle catalysts. Determination of surface oxidic species formed upon CO2 electrocatalytic reduction (if there are)
  • Density functional theory (DFT) simulations of the adsorption of CO2 on the determined surface crystallographic sites.
  • Analysis of the product distribution from CO2 electrocatalytic reduction on different metals and determination of the trend. How to suppress H2 formation?
  • Determination of the impact of different capping agents on the product distribution. Explanation at the molecular level.
  • Design the best catalytic system possible, address scaling up issues, determination of energy efficiency of the system.
  • Correlation of the product distribution with the crystallographic surface sites. Are oxidic species involved?
  • DFT simulations for the reaction mechanism elucidation. Determination of the rate limiting process.
  • Investigate the reaction mechanism experimentally. Checking the accordance of DFT calculations with ATR-IR experiments.


Acknowledgements

The National Research School for Combined Catalysis (NRSCC) is gratefully acknowledged for financial support.

References:

  1. G. Centi and S. Perathoner, Towards solar fuels from water and CO2, ChemSusChem 3 (2010) 195-208.
  2. H. Shibata, Electrocatalytic CO2 reduction, PhD Thesis (2007).
  3. H. Shibata, J.A. Moulijn and G. Mul, Enabling electrocatalytic Fischer-Tropsch synthesis from carbon dioxide over copper-based electrodes, Catal. Lett. 123 (2008) 186-192.
  4. G. Centi and S. Perathoner, Opportunities and prospects in the chemical recycling of carbon dioxide to fuels, Catal. Today 148 (2009) 191-205.
  5. Y. Hori, K. Kikuchi and S. Suzuki, Production of CO and CH4 in electrochemical reduction of CO2 at metal electrodes in aqueous hydrogencatbonate solution, Chem. Lett. (1985) 1695 - 1698.
  6. A. Quintanilla, V.C.L. Butselaar-Orthlieb, C. Kwakernaak, W.G. Sloof, M.T. Kreutzer and F. Kapteijn, Weakly bound capping agents on gold nanoparticles in catalysis: Surface poison?, J. Catal. 271 (2010) 104-114