Carbon dioxide reduction on the composite of copper and praseodymium-doped ceria electrode in a solid oxide electrolysis cells

Abstract

Electrochemical reduction of CO2 is performed in a solid oxide electrolysis cell (SOEC), with Cu-Pr0.1Ce0.9O2-δ (Cu-PDC) composite cathode and La0.8Sr0.2MnO3-δ (LSM) anode on yttria-stabilized zirconia (YSZ) electrolyte. The electrochemical performance of the fabricated SOEC for CO2 reduction is compared with a similar high-temperature SOEC having Cu-infiltrated praseodymium-doped ceria electrode (Neetu et al., ECS Transaction 78, 3329, 2017). On varying the applied potentials and reducing environment at different volumetric ratio of CO2/CO and CO2/H2, electrochemical measurements are carried out to understand the role of reducing atmosphere. On the Cu-PDC composite electrode, a significantly improved reduction current (− 0.84 A cm−2 at Vapp = 2.5 V) is measured as compared to the Cu-infiltrated electrode reported earlier. Oxygen vacancy formation energy on doped ceria surface is calculated, using density functional theory, and found to be relatively lower (∆Evac = 84.6 kJ mole−1) as compared to the un-doped ceria surface (∆Evac = 152.8 kJ mole−1), indicating facile oxygen anion transport in Cu-PDC. Density of state calculations shows Pr substitution in ceria responsible for the reduction in band gap [O(2p) → Ce(4f)] from 1.75 to 0.4 eV, contributing to electronic conduction. The theoretical results thus elucidate the activity of Pr-doped ceria materials for CO2 reduction to CO. The theoretical results combined with experiments conducted on Cu-PDC electrode are therefore expected to provide a basis for the development of a new electrocatalyst for CO2 reduction.