Citation: Macchi, S.; Denmark, I.; Le,
T.; Forson, M.; Bashiru, M.; Jalihal, A.;
Siraj, N. Recent Advancements in the
Synthesis and Application of
Carbon-Based Catalysts in the ORR.
Electrochem 2022, 3, 1–27.
https://doi.org/10.3390/
electrochem3010001
Academic Editor: Masato Sone
Received: 3 December 2021
Accepted: 22 December 2021
Published: 27 December 2021
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electrochem
Review
Recent Advancements in the Synthesis and Application of
Carbon-Based Catalysts in the ORR
Samantha Macchi * , Iris Denmark, Thuy Le , Mavis Forson , Mujeebat Bashiru , Amanda Jalihal
and Noureen Siraj *
Department of Chemistry, University of Arkansas at Little Rock, Little Rock, AR 72204, USA;
isdenmark@ualr.edu (I.D.); ttle@ualr.edu (T.L.); mxforson@ualr.edu (M.F.); mobashiru@ualr.edu (M.B.);
anjarman@ualr.edu (A.J.)
* Correspondence: spmacchi@ualr.edu (S.M.); nxsiraj@ualr.edu (N.S.)
Abstract: Fuel cells are a promising alternative to non-renewable energy production industries such
as petroleum and natural gas. The cathodic oxygen reduction reaction (ORR), which makes fuel cell
technology possible, is sluggish under normal conditions. Thus, catalysts must be used to allow
fuel cells to operate efficiently. Traditionally, platinum (Pt) catalysts are often utilized as they exhibit
a highly efficient ORR with low overpotential values. However, Pt is an expensive and precious
metal, posing economic problems for commercialization. Herein, advances in carbon-based catalysts
are reviewed for their application in ORRs due to their abundance and low-cost syntheses. Various
synthetic methods from different renewable sources are presented, and their catalytic properties
are compared. Likewise, the effects of heteroatom and non-precious metal doping, surface area,
and porosity on their performance are investigated. Carbon-based support materials are discussed
in relation to their physical properties and the subsequent effect on Pt ORR performance. Lastly,
advances in fuel cell electrolytes for various fuel cell types are presented. This review aims to provide
valuable insight into current challenges in fuel cell performance and how they can be overcome using
carbon-based materials and next generation electrolytes.
Keywords: oxygen reduction reaction; fuel cells; doped carbon; renewable energy; carbon catalyst;
electrolyte; membrane
1. Introduction
A key issue for American society is the disparity of the supply and the demand of
energy sources. For instance, the United States consumed 20.5 million barrels of petroleum
per day (mbd) in 2020, which is significantly greater than the 16 mbd it produced [1]. This
disparity leads to the importation of more petroleum each year to supply the growing
energy demand. However, these fossil fuels are not sustainable. These nonrenewable
products can cause detrimental environmental effects due to the production of greenhouse
gas emissions such as carbon dioxide (CO
2
), methane (CH
4
), and ozone. This has led
researchers to investigate alternative and more environmentally friendly methods for the
production, storage, and conversion of energy. In order to avoid the rapid depletion of
energy sources and continue towards a sustainable future, it is paramount that energy
storage and conversion should primarily be performed by renewable means. In the last
three decades, fuel cells have become a crucial technology for production of electrical energy
from clean, renewable sources [2]. Fuel cells offer several advantages over other energy
storage and generation devices such as lithium-ion batteries and flow batteries. Fuels cells
offer a greater energy density compared to either type of battery [3]. In addition, while
lithium-ion batteries are more portable, they suffer from short lifetimes, environmentally
toxic waste products, and low utility at low or high temperatures [4]. Flow batteries
offer significant versatility in that they can be used in a similar way to either fuel cells
or rechargeable batteries. However, they currently utilize toxic or corrosive liquids and
Electrochem 2022, 3, 1–27. https://doi.org/10.3390/electrochem3010001 https://www.mdpi.com/journal/electrochem