Layered and hexagonal perovskites as novel classes of proton-conducting solid electrolytes. A focus review

Abstract

Solid oxide electrolytes have attracted significant attention due to their possible applications in energy conversion devices, including solid oxide fuel cells (SOFCs) and electrolysis cells (SOECs). Although a large amount of data has been accumulated to date, the design of new representatives of ionic electrolytes is of unquenchable interest. In this paper, a review of the new classes of proton-conducting solid electrolytes is provided. The physicochemical and transport properties of layered perovskites (BaNdInO4, BaNdScO4, SrLaInO4, BaLaInO4) and hexagonal perovskites (Ba7Nb4MoO20, Ba5Er2Al2ZrO13 and Ba5In2Al2ZrO13) were analyzed and summarized. Based on the performed analysis, the most promising compositions among the considered phases were identified and the effective approaches aimed at improving their functional characteristics were provided.

Technological Challenges and Advancement in Proton Conductors: A Review

“…Numerous perovskite classes of materials with general skeletal formulas for cation pairing (A + B 2+ O 3-δ , A 2+ B 4+ O 2-δ , A 3+ B 3+ O 2-δ , and A + B 5+ O 2-δ ) are viable as electrolytes for fuel cell applications. 36 The inherent bond flexibility in the ABO 3 crystal structures of perovskite materials with large active B-sites (cationic sites) assists doping for electrochemical reactions. Perovskites are also contemplated as a Re−O 3 type structure constituted via BO 6 corner sharing octahedra with 12 coordinated A-site interstices.…”

“…One of the prime advantages of perovskite material in the context of fuel cell application is the high catalytic activity and ambient electronic and ionic transport properties. Numerous perovskite classes of materials with general skeletal formulas for cation pairing (A + B 2+ O 3‑δ , A 2+ B 4+ O 2‑δ , A 3+ B 3+ O 2‑δ , and A + B 5+ O 2‑δ ) are viable as electrolytes for fuel cell applications . The inherent bond flexibility in the ABO 3 crystal structures of perovskite materials with large active B-sites (cationic sites) assists doping for electrochemical reactions.…”

Novel High Conductive Ceramic Materials Based on Two-Layer Perovskite BaLa2In2O7

“…This provides more flexibility to the layered perovskite structure compared with classic perovskite. The doped compositions based on a monolayer (n = 1) BaLaInO 4 composition can intercalate up to ~2 mol H 2 O per formula unit which is an order of magnitude higher than for acceptor-doped perovskites [ 34 , 35 ]. As previously shown, doped monolayer perovskites BaNdInO 4 [ 36 , 37 , 38 , 39 , 40 ], BaLaInO 4 [ 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ] and SrLaInO 4 [ 49 , 50 , 51 , 52 , 53 ] are prospective ionic (oxygen-ionic and protonic) conductors.…”

“…As previously shown, doped monolayer perovskites BaNdInO 4 [ 36 , 37 , 38 , 39 , 40 ], BaLaInO 4 [ 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ] and SrLaInO 4 [ 49 , 50 , 51 , 52 , 53 ] are prospective ionic (oxygen-ionic and protonic) conductors. However, the acceptor doping in the A-sublattices of AA′BO 4 allows it to achieve higher conductivity values [ 34 , 35 ]. In 2022, two-layer BaLa 2 In 2 O 7 complex oxide was described as an ionic conductor for the first time [ 54 ].…”

Novel Protonic Conductor SrLa2Sc2O7 with Layered Structure for Electrochemical Devices

“…Layered perovskites can be described by the general formula AA' n B n O 3n+1 , where A is the alkali-earth metal, such as barium or strontium, A' is the rare-earth metal, such as lanthanum or neodymium, and B is the trivalent metal, such as indium or scandium. Monolayer perovskites AA'BO 4 (n = 1) were described as protonic conductors several years ago for the first time [30]. Such matrix compositions as BaNdInO 4 [31][32][33][34][35], BaNdScO 4 [36], SrLaInO 4 [37][38][39][40][41], BaLaInO 4 [42][43][44][45][46][47] and compounds based on them were investigated, and general regularities of proton transport in doped monolayer perovskites were revealed [48].…”