Technological Challenges and Advancement in Proton Conductors: A Review

Abstract

Proton conductors (PCs) are multifunctional perovskite materials with structural, electrical, and chemical compatibilities that serve as principal components in proton conducting solid oxide fuel cells (PC-SOFC). The synergetic advantages of PC-SOFC dominate lucrative applications of conventional SOFC. However, adequate advantages accompany certain key limitations in PCs. The inverse interplay between proton conductivity and chemical stability are two broader challenges which demonstrate a clear trade-off. As a consequence, different reactive constituents within the host BaCeO 3 and BaZrO 3 PCs enforce the gradient in chemical stability under diverse atmospheres, while altered charge chemistry and structural perturbations escalate the activation barrier and impose reduced proton conductivity. Such occurrences are more pronounced in acceptor-doped PCs. Although material engineering via acceptor defect substitutions assists protonation and charge dynamics, on the other hand, it provokes novel challenges (proton trapping effect) at a higher dopant volume fraction beyond the threshold. The principal entropy among chemical and electrophysical parameters is proportionally associated with dopant-incorporated subcategorical material limitations. In this study, a compilation of factors responsible for structural and electrophysical diversities as a consequence of compositional-induced symmetry variations is highlighted with a plausible conclusion and future research perspectives for smart and advanced energy applications.

Hydration and Proton Kinetics in Ce-Doped Co-Free Perovskite for the Triple-Conducting Cathode in Solid Oxide Fuel Cells

“…However, due to the high activation energy of oxygen ions in the cathode, the SOFCs usually operate between 800 and 1000 °C, leading to many disadvantages regarding long-term operation, materials stability, cost, and safety . Therefore, developing intermediate-to-low temperature (400–600 °C, ILT) SOFCs becomes a hot spot in SOFC technology, for which many efforts have been devoted to reducing the polarization resistance in ILT by designing new cathode materials. − …”

High-Performance and Robust Composite Cathode via W Doping-Induced Phase Separation for Proton Ceramic Fuel Cells

“…As well-known, SrCoO 3−δ (SC)-based perovskite is seen as one of the most potential cathodes for SOFCs on account of the advantages of sufficiently high electronic and ionic conductivity and adequate activity for ORR. , In the past few years, some well-known SC-based perovskite-type materials possessing mixed electron conductivity and ion conductivity (MIEC), such as SmSrCoO 3−δ (SSC), La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3−δ (LSCF), and Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ (BSCF), have demonstrated their potential as cathodes for O-SOFCs, while exhibiting dissatisfactory performance for PCFCs. − This is mainly due to the insufficient protonic conductivity. Later on, although developing some encouraging cathode materials, realizing widespread popularization and commercial application of PCFC technology is still of great difficulty. , …”

Self-assembly of water-filled molecular saddles to generate diverse morphologies and high proton conductivity

“…6 Designing efficient SSPC materials is crucial for advancing clean and renewable energy technologies and overcoming certain challenges related to conventional proton-conducting systems. 7,8 The current SSPC materials based on metalorganic frameworks (MOFs), [9][10][11][12] carbon-organic frameworks (COFs), [13][14][15][16] polymer electrolytes, [17][18][19] perovskite oxide, [20][21][22][23][24] etc. offer limited solution processability and the use of metal ions can lead to adverse environmental consequences and loss of activity upon leaching of metal ions.…”