Exploring cost-effective and efficient catalysts for oxygen reduction reaction (ORR) poses a significant challenge, especially in the pursuit of alternatives to precious metals like platinum. Significant advancements have driven electrochemists to develop efficient ORR catalysts using abundant materials, particularly iron (Fe)-based, known for their exceptional performance in ORR. While the crucial function of Fe in boosting ORR catalytic activity is recognized, the connection between material attributes and catalytic performance remains enigmatic. Understanding the dynamic processes involved in oxygen electrocatalysis is paramount for designing precious-metals-free ORR electrocatalysts. Mössbauer spectroscopy stands out as a powerful technique for deciphering the structural characteristics of Fe species in catalysis, facilitating the identification of active sites and the clarification of catalytic mechanisms. By showcasing noteworthy case studies within this review, we demonstrate the application of in-situ/operando 57Fe Mössbauer spectroscopy across diverse Fe-involved materials in ORR catalysis. This sheds light on various aspects of ORR catalysis, such as identifying active sites, assessing stability, and understanding the reaction mechanism. Our inquiry drives towards the opportunities and hurdles associated with Mössbauer spectroscopy, unveiling potential breakthroughs and avenues for enhancement within this pivotal research realm.
Ion-solvaing membranes (ISMs) have received extensive attention in recent years as a key component in electrochemical energy conversion and storage devices. This article provides an overview of structural composition, performance advantages, research progress, ion conduction mechanism and existing issues of ISMs, primarily classifying them according to the matrix structure. A detailed analysis of performance enhancement methods, key performance indicators of ISMs and performance influencing factors is also presented. The article contributes to further optimizing the design and application of ion-solvation membranes, providing theoretical support for the development of fields such as hydrogen production through electrolysis of water and electrochemical energy in the future.
Aqueous sodium-ion batteries (ASIBs) have attracted great attention in aqueous batteries due to their merit of high safety. However, the constrained work potential and insufficient chemical stability of anode materials in aqueous electrolytes hinder the large-scale application of ASIBs. Sodium titanium phosphate, NaTi2(PO4)3 (NTP), is considered one of the most promising anode materials for ASIBs due to its excellent electrochemical performance and tunable structure. Recently, great achievements have been made in the development of NTP, however, a comprehensive review of existing studies is still lacking. This article firstly introduces the basic properties of NTP and analyzes the existing challenges. Subsequently, it will provide a comprehensive overview of the key strategies related to the design and modification of NTP materials with optimized electrochemical performance. Finally, based on the current research status and practical needs, suggestions, and future perspectives for advancing NTP in practical applications of ASIBs are presented. This review aims to guide the future research trajectory from basic material innovation to industrial applications, thus promoting the large-scale commercialization of ASIBs.
Proton exchange membrane fuel cells (PEMFCs) are considered as a promising renewable power source. However, the massive commercial application of PEMFCs has been greatly hindered by their high expense and less-satisfied performance mainly due to the sluggish oxygen reduction reaction (ORR) kinetics even on state-of-the-art Pt catalyst. Octahedral PtNi nanoparticles (oct-PtNi NPs) with excellent ORR activity in a half-cell have been widely studied, while their performance in membrane electrode assembly (MEA) has much less reported. Herein, we investigated the MEA performance using the carbon supported oct-PtNi NPs (oct-PtNi/C) as the cathode catalyst. Under the mild acid washing condition, the surface Ni atoms of oct-PtNi/C were largely removed, and the performance of the MEA using the acid-leaching oct-PtNi/C (PNC-A) as the cathode catalyst was greatly improved. The maximum power density of the MEA reached 1.0 W·cm-2 with the cathode Pt loading of 0.2 mg·cm-2, which is 15% higher than that using Pt/C as the catalyst. After 30k cycles in the accelerated degradation test (ADT), the MEA using PNC-A as the catalyst showed a performance retention of 82%, higher than that of Pt/C (74%). The results reported here verify the possibility of using PNC-A as an advanced cathode catalyst in PEMFCs, thus enhancing the performance of PEMFCs while lowering the amount of expensive Pt.