Advancements in cathode catalyst and cathode layer design for proton exchange membrane fuel cells

Abstract

Proton exchange membrane fuel cells have been recently developed at an increasing pace as clean energy conversion devices for stationary and transport sector applications. High platinum cathode loadings contribute significantly to costs. This is why improved catalyst and support materials as well as catalyst layer design are critically needed. Recent advances in nanotechnologies and material sciences have led to the discoveries of several highly promising families of materials. These include platinum-based alloys with shape-selected nanostructures, platinum-group-metal-free catalysts such as metal-nitrogen-doped carbon materials and modification of the carbon support to control surface properties and ionomer/catalyst interactions. Furthermore, the development of advanced characterization techniques allows a deeper understanding of the catalyst evolution under different conditions. This review focuses on all these recent developments and it closes with a discussion of future research directions in the field.

Rationalizing Structural Hierarchy in the Design of Fuel Cell Electrode and Electrolyte Materials Derived from Metal-Organic Frameworks

“…When FeNi-N 6 was prepared with four N atoms coordinated with the metal atoms, there were fewer H 2 O 2 yields and the four-electron process resulted in better catalytic performance and longer operating life. In the majority of active sites in electrocatalysis, Fe dominated while Ni enhanced the cycling stability [43]. It can be concluded that active sites are very important for electrocatalysis [67].…”

“…In order to achieve optimal performance, the proportion of Mn and Zn was adjusted to yield 200 Mn-NC SACs having a life of 1000 h at 0.7 V. Cobalt is another multivalent metal that shows excellent electrocatalytic participation, so the Co-N-C type SACs have also been investigated as catalysts devoid of Fe for H2/O2 fuel cells [78]. By a similar calcination procedure, they were also able to synthesize the Co-N-C catalyst, which behaved similar to the Fe-N-C catalysts and displayed a similar performance to that of the Fe-N-C catalysts owing to the well-distributed CoN4 operating sites, which were afforded by the MOF template [43,62]. In spite of the encouraging catalytic activity of catalysts containing Co-N-C, the presence of agglomerated regions of Co might reduce the intrinsic capabilities of Co and N, which are atomically dispersed within the ZIF-8 precursor, forming a Co-N-C@F127 catalyst after a composition of Plu- As a result of their higher stability and remarkable catalytic activity, other transitionmetal-based catalysts have also been examined in H 2 /O 2 fuel cells.…”

“…They were also able to integrate the sealing and electrical properties of GO into the composite. In a polymer electrolyte membrane fuel cell, MOF composite catalysts produced power densities that were comparable to those of platinum-based catalysts [43]. The NH 2 -MIL-88B and ZIF-8 iron and carbon sources, respectively, were utilized in order to make a structure that was shown to resemble a bamboo structure mimicked by a carbon nanotube complex with Fe-positioned active-site nodes.…”

“…More recently, MOFs have been attractive for ORR applications [38][39][40] where the use of metal ions or clusters and organic connectors can aid the development of advanced catalysts. The porous structure of MOF electrocatalysts facilitates mass transfer in electrochemical reactions, and as a result of the uniform distribution of metal throughout the MOF precursors, the active sites of the catalyst are efficiently utilized [41][42][43][44].…”

“…development of advanced catalysts. The porous structure of MOF electrocatalysts facilitates mass transfer in electrochemical reactions, and as a result of the uniform distribution of metal throughout the MOF precursors, the active sites of the catalyst are efficiently utilized [41][42][43][44].…”