Breaking the selectivity-activity seesaw in ethane oxidative dehydrogenation via the synergetic effects of doping and electrochemical activation

Abstract

The oxidative dehydrogenation (ODH) of alkanes using a solid oxide electrolysis cell (SOEC) has attracted worldwide attention as an efficient method for producing ethylene. Nevertheless, it remains challenging to achieve both a high alkane conversion rate and high ethylene selectivity. In this work, we demonstrate that the combination of doping and electrochemical activation can break this activity–selectivity seesaw and achieve a high ethylene yield. Using Sr₂Ti_0.8(Co_1.2−xFe_x)O_6−δ with different dopants as model electrodes, we show that increasing the Fe content efficiently lowers the oxygen activity by weakening metal–oxygen covalency, downshifting O 2p-band relative to the Fermi level, and increasing the oxygen vacancy formation energy. Such changes result in a lower ethane conversion rate but higher ethylene selectivity for Sr₂Ti_0.8Fe_1.2O_6−δ (STF) compared to electrodes with higher Co content. By increasing the applied potential, we can effectively increase the conversion rate of ethane without sacrificing too much ethylene selectivity. Ultimately, the SOEC with STF anode achieves an ethylene yield of up to 71% at 800 °C at 1.2 V with CO₂ as the oxidant on the cathode side, which is among the highest documented. The insights gained from this study knowledge can guide the rational design of high-temperature electrochemical devices for other small molecule conversion reactions.