An efficient electrode for reversible oxygen reduction/evolution and ethylene electro-production on protonic ceramic...

Protonic ceramic electrochemical cells (PCECs) have demonstrated great promise for applications in the generation of electricity, and the synthesis of chemicals (for example, ethylene). However, enhancing the electrochemical reactions kinetics and stability of PCECs electrodes is one grand challenge. Here, we present a novel electrode material via a co-doping of cesium (Cs) and niobium (Nb) on PrBaCo₂O_6-δ with the composition of PrBa_0.9Cs_0.1Co_1.9Nb_0.1O_6-δ (PBCCN), which naturally decomposes into dual phases of a double-perovskite PBCCN (DP-PBCCN, ∼92.3 wt%) and a single-perovskite Ba_0.9Cs_0.1Co_0.95Nb_0.05O_3-δ (SP-BCCN, ∼7.7 wt%) under typical powder processing conditions. PBCCN exhibits a low area-specific resistance (ASR) value of 0.107 Ω cm², an outstanding performance of 2.04 W cm^-2 in fuel cell (FC) mode, a current density of -2.84 A cm^-2 at 1.3 V in electrolysis cell (EC) mode, and promising reversible operational durability of 53 cycles in ∼212 h at +/- 0.5 A cm^-2 and 650 °C. Cs doping generates more oxygen vacancies and accelerates the oxygen exchange kinetics, while Nb doping effectively enhances the stability, as illustrated by the analyses of X-ray photoelectron spectroscopy, and electrical conductivity relaxations. When applied as the positrode for electrochemical non-oxidative dehydrogenation of ethane (C₂H₆) to ethylene (C₂H₄) on PCECs, it displays an encouraging C₂H₆ conversion of 12.75% and a C₂H₄ selectivity of 98.4% at 1.2 V.