High-Entropy Perovskite as a High-Performing Chromium-Tolerant Cathode for Solid Oxide Fuel Cells

Abstract

To achieve chromium tolerance and high performance, a new series of high-entropy perovskites (HEPs) are investigated as cathode materials for solid oxide fuel cells (SOFCs). Multiple rareearth, alkaline-earth, and high-order transition metal elements are used for the A-site of this ABO 3 structure. A pure phase is achieved through the designed combination of different elements in seven out of eight candidates. Due to the retaining of alkaline-earth elements Sr and/or Ba, the electrical conductivities of these HEPs are in the order of 100 S/cm at 550−700 °C, a value that can practically eliminate the electronic resistance of the porous cathode. Three out of eight candidates show similar or better performance than the (La 0.6 Sr 0.4 )(Co 0.2 Fe 0.8 )O 3−δ (LSCF) benchmark. It is found that A-site elements can cast a substantial influence on the overall performance even with a change as small as 10% of the total cations. It seems that each element has its individual "phenomenal activity" that can be transferred from one candidate to the other in the general setting of the perovskite structure, leading to the best candidate by using the three most active elements simultaneously at the A-site. Excellent Cr tolerance has been observed on the (La 0.2 Sr 0.2 Pr 0.2 Y 0.2 Ba 0.2 )Co 0.2 Fe 0.8 O 3−δ sample, showing degradation of only 0.25%/kh during a 41 day operation in the presence of Cr, while LSCF increases by 100% within the first day in the same condition. X-ray photoelectron spectroscopy discovers no Sr segregation as LSCF is found in this HEP; rather, the active element Y takes more A-sites on the outermost layer after long-term operation.

Compositionally Complex Perovskite Oxides for Solar Thermochemical Water Splitting

“…Note that the seemingly inhomogeneity in EDS maps of some elements such as Sr and Al compared to other elements is owing to the different element interaction volume rather than their inhomogeneous distribution. In general, the configurational entropy of a multicomponent solid solution can be enhanced by mixing a large number of cations ideally in equiatomic proportions and a single solid-solution phase can be stabilized if the entropy contribution overcomes the enthalpy-driven phase separation. ,, Therefore, the phase stability of CCPO after redox cycling is possibly attributed to the entropy stabilization effect, stabilizing a single solid-solution phase and inhibiting precipitation during the thermal or electrochemical redox cycling. − For the practical STCH applications, the diurnal cycle of sunlight irradiation should be considered without the viable, efficient, large-scale, and stable thermal energy storage technology − as the STCH materials may subject to drastic temperature swing between elevated temperatures under an 8 h strong sunlight irradiation (operation mode) in the day and low temperatures of long-time cooling stage (downtime mode) in the night. In stark contrast to the ideal uninterrupted cycling condition using a stable heat source, such interrupted cycling involving startup heating and shutdown cooling is a harsh condition to the STCH application, which can induce thermal fatigue, impair the structural integrity, and dramatically deteriorate the H 2 production cycle. , A similar challenge exists in other solar-driven hydrogen production technologies such as photovoltaic-driven water electrolysis, where the startup and shutdown cycling due to the day–night cycle causes degradation of electrocatalysts. − Therefore, the interrupted cycling stability of LS_MFC 0.4 A for thermochemical hydrogen production was evaluated under the daily startup and shutdown cycling for 13 days (51 cycles) to simulate the real diurnal cycle.…”

A review of progress in proton ceramic electrochemical cells: material and structural design, coupled with value-added chemical production

“…9(g)). 172 The PCEC with added interlayer generally exhibits a higher OCV and a reduced interfacial resistance, as well as enhanced electrochemical performance. However, whether the chemical reaction and electrochemical corrosion of the additional interlayer at high temperature would result in delamination and degradation requires further investigation.…”

Atomistic Insights into Medium-Entropy Perovskites for Efficient and Robust CO2 Electrolysis

“…Most recently, a novel family of medium- or high-entropy oxides has sparked great interest owing to their tunable electronic structure through the manipulation of configurational entropy. Leveraging the structural tolerance of perovskites, multicomponent synergy, and the configuration entropy effect, medium- or high-entropy perovskite oxides have been developed as available electrocatalysts for oxygen electrocatalysis. − For example, medium-entropy SrFe 0.25 Ti 0.25 Co 0.25 Mn 0.25 O 3−δ perovskites delivered enhanced structural stability but slightly reduced the oxygen reduction kinetics for solid oxide fuel cells . High-entropy Pr 1/6 La 1/6 Nd 1/6 Ba 1/6 Sr 1/6 Ca 1/6 CoO 3−δ perovskites demonstrated accelerated oxygen reduction and evolution activities for reversible protonic ceramic fuel and electrolysis cells .…”