Tuning Exsolution of Nanoparticles in Defect Engineered Ruddlesden–Popper oxides for efficient CO2 electrolysis

Abstract

Solid oxide cell (SOC) is the energy conversion device with a series of advantages such as high efficiency, environmental friendliness and durability, making it a promising way to deal with environmental pollution and energy crisis appearing with the development of human society. Perovskite oxides with hetero-phases which were prepared by in-situ exsolution are widely used as fuel electrode in SOC. In this work, Ni-doped perovskites Ruddlesden–Popper oxides, (La, Sr)nTinO3n-2 with n = 5, 8, and 12 (LSTNn), were synthesized to design novel exsolution materials as solid oxide fuel cell anodes and for electrochemical catalysis applications.Compared with pure LSTNn without Ni, a small A-site deficiency (10%) promoted the exsolution of Ni from the perovskite oxides of Ni-doped LSTNn. It is found that the morphology as well as electrochemical activity of LSTNn anodes can be successfully manipulated by the exsolution of Ni. Since more Ni nanoparticles are exsolved from the parent oxides, LSTN8 displays better electrochemical performance by providing more active sides during the hydrogen oxidation reaction and significantly lowering electrode polarization resistance. DRT analysis is conducted to study substeps of the whole electrode reaction, finding that in-situ precipitation improves rate-limiting steps much. The CO2 reduction reaction performance of LSTN materials is also studied, finding that in-situ grown nanoparticles on surface of LSTN significantly increases the density of surface active sites and three phase boundaries (TPBs), which are beneficial for CO2 adsorption and subsequent conversion.It is clear from these results that varying Ni-doping in Ruddlesden–Popper oxides is a key factor in controlling the electrochemical performance and catalytic activity for hydrogen oxidation reaction in solid oxide fuel cells.