Recent Advances in Electrocatalysts for Oxygen Reduction Reaction

Abstract

The recent advances in electrocatalysis for oxygen reduction reaction (ORR) for proton exchange membrane fuel cells (PEMFCs) are thoroughly reviewed. This comprehensive Review focuses on the low- and non-platinum electrocatalysts including advanced platinum alloys, core-shell structures, palladium-based catalysts, metal oxides and chalcogenides, carbon-based non-noble metal catalysts, and metal-free catalysts. The recent development of ORR electrocatalysts with novel structures and compositions is highlighted. The understandings of the correlation between the activity and the shape, size, composition, and synthesis method are summarized. For the carbon-based materials, their performance and stability in fuel cells and comparisons with those of platinum are documented. The research directions as well as perspectives on the further development of more active and less expensive electrocatalysts are provided.

Electrocatalytic Metal–Organic Frameworks for Energy Applications

“…[111,112] The ORR proceeds through four proton-electron transfers to transform O 2 into water [Eq. (9)].…”

“…[111,112] The design of new inexpensive catalysts must focus on operating at low overpotentials with high stability,e fficiency,a nd selectivity for the four-electron process [Eq. (9)] versust he two-electron process [Eq.…”

Design of Iron(II) Phthalocyanine‐Derived Oxygen Reduction Electrocatalysts for High‐Power‐Density Microbial Fuel Cells

“…For M−N−C catalysts, there are several synthesis methods, which can be divided into two categories. The first and most common method is based on the high‐temperature treatment (pyrolysis) of a metal salt and organic precursors rich in nitrogen and carbon (N−C precursors) 39. For the last ten years, earth‐abundant transition metals such as Co, Mn, Ni, and Fe were used for the preparation of M−N−C‐type catalysts 40, 41.…”

“…The second method for the preparation of PGM‐free catalysts is based on the modification of carbonaceous supports such as carbon black (CB), carbon nanotubes (CNTs), or graphene with metal complexes such as Fe or Co porphyrins and phthalocyanines with preformed Fe−N x centers 39, 44, 52, 57, 60, 61, 62, 63. This method of ORR catalyst design has been discussed in several articles39,44; the metal centers bound to the nitrogen atoms in the complex act as the active sites, whereas the conductive carbonaceous support improves the electron transfer 39,44.…”

“…This method of ORR catalyst design has been discussed in several articles39,44; the metal centers bound to the nitrogen atoms in the complex act as the active sites, whereas the conductive carbonaceous support improves the electron transfer 39,44. These materials are very active towards the ORR but do not show high stability under different pH conditions.…”