Over the past few years, electrochemical reduction of CO₂ (ERC) has attracted a lot of interest among researchers to convert CO₂ into value added products using renewable energy.¹ Thermodynamic reduction potential of ERC is close to that of hydrogen reduction potential (HER). Moreover, ERC can lead to many products i.e. CO, CH₄, C₂H₄, C₂H₆, HCOOH, CH₃OH etc. depending upon the catalyst and reaction conditions.² Hence, catalysts play a crucial role in selective electroreduction of CO₂. Therefore, majority of the research has been carried out on developing catalyst for selective ERC and most of the studies were conducted in aqueous phase ERC.³ The main limitation of this approach is the CO₂ mass transfer limitations due to the low solubility of CO₂ in water. However, sufficient studies relevant to the technological development of the direct gas phase ERC are still needed.

In this presentation we will discuss our work on role of pressure in improving gas phase ERC carried out in zero gap cell. We have synthesised ZnO/CuO nanocomposite and ZnO nanoparticles by two methods (wet chemical method and hydrothermal method). We have also synthesised a polyethyleneimine (PEI) based anion exchange membrane. Setup was systematically tested at various operating conditions. Results show that CO₂ adsorption on the catalyst aided by the amine functional groups on membrane can be further enhanced by increasing the pressure. As the pressure slightly elevated to 0.5 bar from ambient pressure, HER was supressed and CO faradaic efficiency (FE_CO) of ~30% was reached. Moreover, current density was increased to ~50mA/cm² from 4 mA/cm². In this presentation we will compare the FE_CO, conversion and current densities of the synthesised electrocatalyst and seek to describe how elevating pressure increases rate of ERC on particular catalyst.

References

1. D. Raciti and C. Wang, ACS Energy Lett., 3, 1545-1556 (2018).
2. L.M. Aeshala, R. U. and A. Verma, Phys. Chem. Chem. Phys., 16,17588 (2014).
3. B. Kim, F. Hillman, M. Ariyoshi, S. Fujikawa and P.J.A. Kenis, J. Power Sources, 312, 192 – 198 (2016).