Preparation of anodic catalysts via in situ exsolution of Pt nanoparticles for a methane oxidation enhanced SOEC process

Abstract

Introducing methane at the anode side of a solid oxide electrolysis cell (SOEC) has been proven to effectively suppress the oxygen evolution reaction (OER), thereby enabling hydrogen production at significantly lower voltages. In this work, a double perovskite oxide, Sr₂Fe_1.4Pt_0.1Mo_0.5O_6-δ (abbreviated as Pt-SFM), was successfully synthesized by a liquid-phase method and employed as both an electronic conductor and a catalyst for methane oxidation at the SOEC anode. Following high-temperature treatment under a reducing atmosphere, platinum (Pt) nanoparticles were exsolved from the perovskite lattice and uniformly dispersed on the oxide surface. These exsolved Pt nanoparticles act as highly active sites for methane adsorption and oxidation. Electrochemical performance tests were conducted at 1123.15 K, and the results demonstrated that the Pt-SFM cell treated for 20 h (Pt-SFM 20 h) achieved a current density of 0.85 A·cm⁻² at an applied voltage of 1.40 V. This performance corresponds to a 102.4% enhancement compared to the undoped SFM 20 h cell. The superior performance is attributed to the presence of exsolved Pt, which significantly improves the catalyst's ability to adsorb and dissociate methane molecules. Electrochemical impedance spectroscopy (EIS) analysis under open-circuit conditions revealed that the polarization impedance of the Pt-SFM 20 h cell was 1.25 Ω·cm², which is 49.2% lower than that of the SFM 20 h cell. Furthermore, a 45-h long-term stability test showed that the Pt-SFM 20 h cell maintained a stable performance, with a low voltage degradation rate of only 0.67 mV·h⁻¹.