The chemical durability of the membrane is a central issue in the development of proton exchange membrane fuel cells (PEMFCs), while incorporating cerium oxide as a free radical scavenger is one effective strategy to enhance durability. However, simultaneous dispersion and anchoring of cerium oxide in PEM have rarely been reported. Herein, MXene−CeO 2 hybrids are prepared by self-assembly-cooperating in situ nucleation growth routes, then the MXene−CeO 2 is sprayed on the cathode side of the r-PEM to fabricate a hybrid membrane with free radical resistance. The in situ nucleation growth of CeO 2 on MXene nanosheets carriers effectively inhibits agglomeration and induces an anchoring effect through their interaction forces, forming CeO 2 nanoparticles with a high specific surface and stable attachment, maximizing the free radical scavenging impact at the forefront of the membrane. The hybrid membrane with a loading of 0.1 mg cm −2 MXene−CeO 2 exhibits a lower OCV decay rate (0.53 mV h −1 ), thickness variation (2.8%), and hydrogen crossover (2.6 mA cm −2 ) and higher maximum power density (1222.5 mW cm −2 ) than pristine r-PEM after accelerated degradation testing for 150 h.

The development of rapid and dependable proton transport channels is crucial for proton exchange membrane fuel cells (PEMFCs) operating in low humidity conditions. Herein, an NH-Zr framework rich in basic sites was in situ constructed in a per uorosulfonic acid (PFSA) solution, and PFSA-NH-Zr hybrid proton exchange membranes were prepared. The introduced NH-Zr framework successfully induced proton conducting groups (-SO 3 H) reorganization along the NH-Zr framework, resulting in the formation of fast ion transport channels. Meanwhile, under low humidity, the acid-base pairs between N-H (NH-Zr framework) and -SO 3 H (PFSA) promoted the protonation/deprotonation and the subsequent proton leap via the Grotthuss processes. Especially, the hybrid membrane PFSA-NH-Zr-1 with suitable NH-Zr content had a promising proton conductivity of 0.031 S/cm at 80°C, 40% RH, and 0.292 S/cm at 80°C, 100% RH, which were approximately 33% and 40% higher than the pristine PFSA membrane (0.023 S/cm and 0.209 S/cm), respectively. In addition, the maximum power density of the hybrid proton exchange membrane was 0.726 W/cm 2 , which was nearly 20% higher than the pristine PFSA membrane (0.604 W/cm 2 ) under 80°C, 40% RH. This work established a referable strategy for developing high-performance proton exchange membranes under low RH conditions.

Inadequate water balance causes water flooding in a fuel cell, leading to performance degradation. The hydrophilic channel volume is crucial to the proton conductivity of PEM, especially under a high water concentration gradient. Herein, the volume of the hydrophilic channel was controlled and optimized through adjusting the collocation of resins with different side-chain lengths, with the length acting as a key parameter for the in-depth research on the proton conductivity performance of PEMs. Membranes with different hydrophilic channel volumes were prepared and suggested that the volume of the hydrophilic channel boosted as the increase of the length gap between the matched side chains, which would benefit to proton conductivity of membrane. This study provides guidance for the structural design of proton exchange membrane with cell-flooding resistance and efficient proton conduction at a high water concentration gradient.

Electrochemical water splitting has wide applicability in preparing high-density green energy. The Proton exchange membrane (PEM) water electrolysis system is a promising technique for the generation of hydrogen due to its high electrolytic efficiency, safety and reliability, compactness, and quick response to renewable energy sources. However, the instability of catalysts for electrochemical water splitting under operating conditions limits their practical applications. Until now, only precious metal-based materials have met the requirements for rigorous long-term stability and high catalytic activity under acid conditions. In this review, the recent progress made in this regard is presented and analyzed to clarify the role of precious metals in the promotion of the electrolytic decomposition of water. Reducing precious metal loading, enhancing catalytic activity, and improving catalytic lifetime are crucial directions for developing a new generation of PEM water electrolysis catalysts. A summary of the synthesis of high-performance catalysts based on precious metals and an analysis of the factors affecting catalytic performance were derived from a recent investigation. Finally, we present the remaining challenges and future perspectives as guidelines for practical use.