Designing High Interfacial Conduction beyond Bulk via Engineering the Semiconductor–Ionic Heterostructure CeO_2−δ/BaZr_0.8Y_0.2O₃ for Superior Proton Conductive Fuel Cell and Water Electrolysis Applications

Abstract

Proton ceramic fuel cells (PCFCs) are an emerging clean energy technology; however, a key challenge persists in improving the electrolyte proton conductivity, e.g., around 10–3–10–2 S cm–1 at 600 °C for the well-known BaZr0.8Y0.2O3 (BZY), that is far below the required 0.1 S cm–1. Herein, we report an approach for tuning BZY from low bulk to high interfacial conduction by introducing a semiconductor CeO2−δ forming a semiconductor–ionic heterostructure CeO2−δ/BZY. The interfacial conduction was identified by a significantly higher conductivity obtained from the BZY grain boundary than that of the bulk and a further improvement from the CeO2−δ/BZY which achieved a remarkably high proton conductivity of 0.23 S cm–1. This enabled a high peak power of 845 mW cm–2 at 520 °C from a PCFC using the CeO2−δ/BZY as the electrolyte, in strong contrast to the BZY bulk conduction electrolyte with only 229 mW cm–2. Furthermore, the CeO2−δ/BZY fuel cell was operated under water electrolysis mode, exhibiting a very high current density output of 3.2 A cm–2 corresponding to a high H2 production rate, under 2.0 V at 520 °C. The band structure and a built-in-field-assisted proton transport mechanism have been proposed and explained. This work demonstrates an efficient way of tuning the electrolyte from low bulk to high interfacial proton conduction to attain sufficient conductivity required for PCFCs, electrolyzers, and other advanced electrochemical energy technologies.

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

“…This phenomenon is more prominent near the interface, signifying increased oxygen vacancies resulting from forming a heterojunction. The two distinct peaks in the oxygen position indicate different chemical environments, namely oxygen vacancies (O V ) and lattice oxygen (O L ). , The peak around 528.0 eV is related to the lattice oxygen, while the peak at 531 eV is related to the O vacancies . BTO–10CeO 2 exhibits the highest oxygen vacancy region/total area ratio of all of the samples, reaching 0.88.…”

Highly Immobilized Bimetallic Fe/M‐N4 (M‐ Mg or Zn) Conductive Metal–Organic Frameworks on Nitrogen‐Doped Porous Carbon for Efficient Electrocatalytic Hydrogen Evolution and Oxygen Reduction Reactions

“…Synthesis of Amine-Functionalized Nano Zn-MOF: Amine-functionalized nano-MOF-5 (Zn) was synthesized by ligand exchange of H 2 BDC with the postsynthetic modification method. [3] Activated MOF-5 (Zn) of 0.4 g was well dispersed in 200 mL of methanol and kept under sonication for 30 min, and then Atz ligand (1.1 g) was added to the nano-MOF-5 suspension. The synthesis reaction was carried out for a certain reaction time at 50 °C for 24 h. Finally, the obtained product was collected by centrifugation, washed three times with methanol, and dried at 70 °C for 3 days under vacuum.…”

“…Clean and renewable energy using water electrolysis and fuel cells is widely recognized as a viable solution to meet the growing energy demand and address the environmental crisis resulting from the depletion of fossil fuels. [1][2][3] Water electrolysis is a promising technology for renewable energy sources, enabling efficient production, transportation, and storage of hydrogen energy. The water-electrolysis process comprises two half-cell reactions: the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).…”

Designing Proton Conducting Electrolytes for Low-Temperature Ceramic Fuel Cells

“…Increased O-vacancies on the surface of Bi-doped CeO 2 are also attributed to the higher area of Ce 3+ in the BDC compared to the CeO 2 . 8,26,32,40 Furthermore, the O 1s spectra of CeO 2 and BDC are shown in Figure 9d,e, where the OI peak at 528.5 eV is related to the lattice oxygen, the OII peak at 530.4 eV is associated with the surface oxygen defects, and the OIII peak at 532 eV is related to the surface oxide species adsorption on the O-vacancies. The more extensive region of the O 1s spectra of BDC over CeO 2 demonstrates that the chemisorbed O-species are greater in BDC.…”

“…The resistances at the Ohmic, grain boundary, and electrode levels are said to intersect at the crossover point between higher and lower frequencies in the existing literature. 40,41 The circuit…”