Doping strategies on perovskite oxides as electrocatalysts for CO2RR

Clean energy transition points to renewable energy systems, CO2 utilisation and storage as energy vectors and chemicals. The development of innovative technologies like solid oxide cells (SOCs) able to produce green energy and/or convert CO2 into valuable fuels is vital for the next near future. Reversible SOCs work in solid oxide fuel cells (SOFCs) mode for producing green energy and in solid oxide electrolysis cells (SOECs) mode for recycling CO2 [1]. Perovskite oxides with nominal formula of AA’BB’O3 have been recognized as one of most promising class of electrocatalysts for SOCs application [2]. The present work deals with doping strategies for the fine-tuning of perovskite electrode materials able to activate the electrochemical CO2 reduction reaction (CO2RR). La0.6Sr0.4Fe0.8- xMxCo0.2O3-yFy powders were doped by three different strategies: i) doping the B-site with Cu or Ni (x=0, 0.1); ii) fluorine-doping in O site (y=0, 0.1); and iii) co-doping B- and O-sites with Cu/Ni and F (x=0, 0.1; y=0, 0.1). Solution combustion synthesis (SCS) and complexing citrate method were employed as effective synthesis methods in producing perovskite oxides. X-ray diffraction associated with Rietveld analysis method evidenced the incorporation of Cu, Ni and F in the rhombohedral perovskite crystal structure (Figure 1). H2-temperature programmed reduction profiles showed that this class of materials exhibits reduction properties and oxygen mobility in the SOCs working temperature range. The role of doping strategies on oxygen vacancies distribution evaluated by O2- and CO2- thermogravimetric analyses hinted at positive effect of copper and fluorine doping (Figure 1). Electrochemical impedance spectroscopy under pure CO2 atmosphere on symmetrical cells configuration with Ce0.8Sm0.2O2 as electrolyte revealed ASR value as low as 1.0 Ωcm2 at 850 °C (Figure 1).