Successful Manufacturing Protocols of N-Rich Carbon Electrodes Ensuring High ORR Activity: A Review

Abstract

The exploration and development of different carbon nanomaterials happening over the past years have established carbon electrodes as an important electrocatalyst for oxygen reduction reaction. Metal-free catalysts are especially promising potential alternatives for replacing Pt-based catalysts. This article describes recent advances and challenges in the three main synthesis manners (i.e., pyrolysis, hydrothermal method, and chemical vapor deposition) as effective methods for the production of metal-free carbon-based catalysts. To improve the catalytic activity, heteroatom doping the structure of graphene, carbon nanotubes, porous carbons, and carbon nanofibers is important and makes them a prospective candidate for commercial applications. Special attention is paid to providing an overview on the recent major works about nitrogen-doped carbon electrodes with various concentrations and chemical environments of the heteroatom active sites. A detailed discussion and summary of catalytic properties in aqueous electrolytes is given for graphene and porous carbon-based catalysts in particular, including recent studies performed in the authors’ research group. Finally, we discuss pathways and development opportunities approaching the practical use of mainly graphene-based catalysts for metal–air batteries and fuel cells.

Defect engineering in carbon materials for electrochemical energy storage and catalytic conversion

“…100 To date, a large number of experimental and theoretical papers on metal-free heteroatom doping modified carbon materials have been published. [101][102][103][104][105] The doping effect imparts high charge density and spin density to surrounding carbon atoms, which act as active sites to improve electrochemical reactivity. [106][107][108] Based on the comparison of electronegativity between doped atoms and C atoms, the effects of doping sites can be divided into charge-dominated, electron-spin-dominated, and charge-spin coupling mechanisms (Fig.…”

Biomass‐Derived Electrocatalysts: Low‐Cost, Robust Materials for Sustainable Electrochemical Energy Conversion

“…Current commercial carbon materials sourced from petrochemical products require specialized synthesis equipment. [7,19,[47][48][49][50][51] For instance, commercial carbon black is typically produced by spraying oil feedstock onto the inner walls of a hightemperature furnace for carbonization, often at temperatures exceeding 1000 °C. [52] On the other hand, the production of commercial carbon nanotubes (CNTs) involves various methods, including arc discharge, laser ablation, chemical vapor deposition, and high-pressure carbon monoxide disproportionation.…”

“…Therefore, the limited source of raw materials, high costs, and complex synthesis pathways severely restrict the large-scale application of these carbon materials. [7,19,[47][48][49][50][51] However, carbon is abundant and widespread in the biosphere, forming the fundamental structure of all living organisms. [17,46,47,51,55,56] Using low-cost, renewable biomass as raw materials, which include proteins (such as hemoglobin, collagen, and so on) and polysaccharides (such as chitin, cellulose, and so on), to synthesize carbon materials for use in electrocatalysis has great potential and advantages.…”

“…[7][8][9][10][11][12][13][14][15] However, the electrochemical reactions involved in these technologies, such as the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR), are typically uphill thermodynamic processes, requiring substantial reaction barriers to be overcome to increase overall efficiency. [1,6,[16][17][18][19][20][21][22] Electrocatalytic materials have been used extensively to tackle this challenge. In new energy technologies, traditional platinum group metals (PGMs), including ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt), are widely used as catalysts owing to their exceptional electrocatalytic properties.…”

Modified graphene foam as a high-performance catalyst for oxygen reduction reaction

“…The intensity of the D-band indicates a defected structure of the material. As described in an earlier literature review 20 the interaction between nitrogen and the neighboring carbon is signicant. The introduction of nitrogen into the sp 2 carbon structure alters the electronic properties of the carbon atoms due to the higher electronegativity of nitrogen.…”