Ni/NiO Exsolved Perovskite La_0.2Sr_0.7Ti_0.9Ni_0.1O_3−δ for Semiconductor-Ionic Fuel Cells: Roles of Electrocatalytic Activity and Physical Junctions

Abstract

A semiconductor-ionic fuel cell (SIFC) is recognized as a promising technology and an alternative approach to reduce the operating temperature of solid oxide fuel cells. The development of alternative semiconductors substituting easily reduced transition metal oxide is a great challenge as high activity and durability should be satisfied simultaneously. In this study, the B-site Ni-doped La0.2Sr0.7Ti0.9Ni0.1O3−δ (LSTN) perovskite is synthesized and used as a potential semiconductor for SIFC. The in situ exsolution and A-site deficiency strategy enable the homogeneous decoration of Ni/NiO nanoparticles as reactive sites to improve the electrode reaction kinetics. It also supports the formation of basic ingredient of the Schottky junction to improve the charge separation efficiency. Furthermore, additional symmetric Ni0.8Co0.15Al0.05LiO2−δ (NCAL) electrocatalytic electrode layers significantly enhance the electrode reaction activity and cells’ charge separation efficiency, as confirmed by the superior open circuit voltage of 1.13 V (close to Nernst’s theoretical value) and peak power density of 650 mW cm–2 at 550 °C, where the latter is one order of magnitude higher than NCAL electrode-free SIFC. Additionally, a bulk heterojunction effect is proposed to illustrate the electron-blocking and ion-promoting processes of the semiconductor-ionic composite electrolyte in SIFCs, based on the energy band values of the applied materials. Overall, we found that the energy conversion efficiency of novel SIFC can be remarkably improved through in situ exsolution and intentional introduction of the catalytic functionality.

Space Charge Polarization Effect in Surface-Coated BaTiO3 Electrolyte for Low-Temperature Ceramic Fuel Cell

“…Perovskite semiconductors have also shown promise as electrolytes for low-temperature CFCs, such as the SrFe 0.2 Ti 0.8 O 3 –ZnO heterostructure demonstrated by Shah et al . Using semiconductor-based materials in ceramic fuel cells offers significant advantages, including enhanced ionic conducting properties and a built-in electric field (BIEF) that prevents electronic short-circuiting and promotes ion transportation. − Among these materials, BaTiO 3 , a widely studied perovskite, possesses high dielectric constant and ferroelectric properties, making it suitable for various electronic and electro-optical applications. − Using high dielectric materials with large polarizability to develop oxide-ion electrolytes has also emerged. , An exciting strategy was needed to advance CFCs, and this study presents an approach using a BaTiO 3 (BTO) coating, incorporating the wide band gap ion-conducting semiconductor material CeO 2 as a promising electrolyte layer for CFCs. The authors also investigated the surface and interfacial properties of the BTO–CeO 2 interfaces to enhance ionic conductivity and realize a successful fuel cell operation.…”

Electrochemical Properties of La0.6A0.4Co0.2Fe0.8O3 (A = Sr, Ca, Ba) as a Bifunctional Electrode for Reversible Solid Oxide Cells

“…Therefore, a new type of cell structure can be constructed by reducing the operating temperature to solve the above two problems. 4,5 The traditional fuel cell is a three-layer structure. Zhu et al reported a new type of cell structure: single-component fuel cell (SCFC), which is composed of a semiconductor and ionic conductor material.…”

“…However, the high-temperature operation will increase the requirements for cell modules and increase cell costs. Therefore, a new type of cell structure can be constructed by reducing the operating temperature to solve the above two problems. , …”

Improving Electrochemical Oxidation/Reduction Kinetics in Single-Component Solid Oxide Cells through Synergistic A-Site Defects and Anion Doping

“…Semiconductor materials play a vital role in the reactions taking place at both electrodes and therefore have specific structural and activity requirements. 11,12 In general, electrode materials must have excellent catalytic oxidation and reduction activity, as well as good stability under high temperature and high humidity conditions. Among these materials, the perovskite La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) oxide has gained wide recognition and usage due to its acceptable hydrogen oxidation/oxygen reduction activity and good tolerance against moisture atmosphere.…”

“…Commonly used electrolyte materials in single-component SOCs include Sm 0.2 Ce 0.8 O 2−δ (SDC) and SDC-carbonate. Semiconductor materials play a vital role in the reactions taking place at both electrodes and therefore have specific structural and activity requirements. , In general, electrode materials must have excellent catalytic oxidation and reduction activity, as well as good stability under high temperature and high humidity conditions. Among these materials, the perovskite La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3‑δ (LSCF) oxide has gained wide recognition and usage due to its acceptable hydrogen oxidation/oxygen reduction activity and good tolerance against moisture atmosphere. , Recently, various strategies have been explored to enhance the catalytic activity of electrode materials for both conventional and single-component SOCs. − For example, introducing A-site defects in (La 0.6 Sr 0.3 )­CrO 3‑δ hydrogen electrode material has been shown to significantly enhance the concentration of oxygen vacancies, thus improving catalytic activity .…”