Electrochemical Performance of Pr_(0.4)Sr_(0.5)Co_xFe_(0.9-x)Mo_(0.1)O_(3-δ) Oxides in a Reversible SOFC/SOEC System

摘要

Changing the type and content of cation doping in perovskite oxide can improve its electrocatalytic performance in various environmental and energy devices. In this study, perovskite oxides Pr_(0.4)Sr_(0.5)Co_xFe_(0.9-x)Mo_(0.1)O_(3-δ) (PSCFM, x = 0.1, 0.2, 0.45, and 0.7) are synthesized and act as semiconductors of single-component fuel cells (SCFCs) and reversible single component cells (RSCCs). Under reducing conditions, the CoFe alloy nanoparticles are exsolved in situ and uniformly distributed on the perovskite surface. With the change of Co doping amount, the alloy types and particle sizes are varied. As the main place of electrochemical reaction, oxygen vacancy affects the catalytic activity of electrode materials. For the reduced PSCFM (R-PSCFM), the oxygen vacancy concentration decreases first and then increases with the increase in Co content. With a moderate Co doping level, Pr_(0.4)Sr_(0.5)Co_xFe_(0.9-x)Mo_(0.1)O_(3-δ) displays the best catalytic activity for hydrogen oxidation reaction (HOR) and Pr_(0.4)Sr_(0.5)Co_xFe_(0.9-x)Mo_(0.1)O_(3-δ) shows the best catalytic performance for oxygen reduction reaction (ORR). In addition, the rate-determining step (RDS) of HOR is a mixture of oxygen surface exchange and charge transfer reaction, and for ORR, the RDS is the reduction of oxygen atoms to O~-. Furthermore, when the semiconductor material composition is Pr_(0.4)Sr_(0.5)Co_xFe_(0.9-x)Mo_(0.1)O_(3-δ), the best performance characterized by high output power and electrolysis current density can be obtained under the SOFC/SOEC reversible operation.