Carbon‐Based Electrocatalysts for Acidic Oxygen Reduction Reaction

Abstract

Oxygen reduction reaction (ORR) is vital for clean and renewable energy technologies, which require no fossil fuel but catalysts. Platinum (Pt) is the best‐known catalyst for ORR. However, its high cost and scarcity have severely hindered renewable energy devices (e.g., fuel cells) for large‐scale applications. Recent breakthroughs in carbon‐based metal‐free electrochemical catalysts (C‐MFECs) show great potential for earth‐abundant carbon materials as low‐cost metal‐free electrocatalysts towards ORR in acidic media. This article provides a focused, but critical review on C‐MFECs for ORR in acidic media with an emphasis on advances in the structure design and synthesis, fundamental understanding of the structure‐property relationship and electrocatalytic mechanisms, and their applications in proton exchange membrane fuel cells. Current challenges and future perspectives in this emerging field are also discussed.

Recent advances in atomically precise metal nanoclusters for electrocatalytic applications

“…The fuel cell reaction (FCR) is a vital step in converting the chemical energy of fuels into clean and stable electricity and has extensive applications in transportation and energy storage. [54][55][56] NCs have been employed as efficient catalysts in the FCR in recent years, benefiting from their high specific surface area, uniform size and well-defined structure. In 2018, Lu et al investigated the catalytic activity difference between Au 25 and Pt 1 Au 24 NCs for formic acid oxidation (FAO).…”

Intrinsic Carbon Defects in Nitrogen and Sulfur Doped Porous Carbon Nanotubes Accelerate Oxygen Reduction and Sulfur Reduction for Electrochemical Energy Conversion and Storage

“…Carbon-based materials have been widely investigated as both ORR and SRR catalysts and gained more focus owing to their good conductivity, flexible structural tailorability, and curtailed cost. 18,19 However, pristine bulky carbon materials show poor catalytic activity due to a low specific surface area and weak adsorption affinity to oxygen and sulfur. The electrochemical performance of carbon-based materials can be greatly boosted by morphology and type of active site engineering, such as construction of nanoscale architectures and incorporation of defects.…”

“…Incorporation of effective electrocatalysts in cathodes can optimize the adsorption/desorption of reactant/product species, reduce the activation energy of the reduction reactions, and expedite the electrochemical kinetics during the reduction processes. − Although platinum (Pt)-based materials are the most effective commercialized ORR electrocatalysts, , their large-scale application is limited by the scare reserves and exorbitant price; hence, high-performance and cheap ORR electrocatalysts are urgently needed. Carbon-based materials have been widely investigated as both ORR and SRR catalysts and gained more focus owing to their good conductivity, flexible structural tailorability, and curtailed cost. , However, pristine bulky carbon materials show poor catalytic activity due to a low specific surface area and weak adsorption affinity to oxygen and sulfur. The electrochemical performance of carbon-based materials can be greatly boosted by morphology and type of active site engineering, such as construction of nanoscale architectures and incorporation of defects. − Carbon-based materials with various nanostructures of high specific surface area and large pore volume, including nanosheets, , nanoscrolls, nanofibers, , nanotubes, − nanorods, hollow nanospheres, − nanocubes, nanocages, etc., have been constructed to expose more active sites, accommodate more reactants and products, and facilitate mass transfer.…”

Effective construction of a B and N co-doped 3D porous carbon metal-free oxygen reduction reaction catalyst by a secondary pyrolysis strategy

“…Carbon-based metal-free catalysts are one of the most promising alternative materials to precious metal/transition metal-based catalysts due to the non-occurrence of metal dissolution and metal ion contamination, together with exhibiting a high electrical conductivity and tailorable electron configuration by doping various non-metal heteroatoms such as N, S, P, B, Cl, Br, etc. [10][11][12][13][14][15][16][17][18] Among the many non-metallic catalysts, nitrogen-doped carbon (NC) nanomaterials are the first to be discovered, 19 and are also the most deeply investigated. Generally, efficient N doping can cause the redistribution of charge as well as a change of electron spin density of adjacent C atoms, which leads to NC materials delivering outstanding ORR performance.…”