Ten years of carbon‐based metal‐free electrocatalysts

Abstract

Since the discovery of the first carbon-based metal-free electrocatalysts (C-MFECs, i.e., N-doped carbon nanotubes) for the oxygen reduction reaction in 2009, the field of C-MFECs has grown enormously over the last 10 years.C-MFECs, as alternatives to nonprecious transition metals and/or precious noble metal-based electrocatalysts, have been consistently demonstrated as efficient catalysts for oxygen reduction, oxygen evolution, hydrogen evolution, carbon dioxide reduction, nitrogen reduction, and many other (electro-) chemical reactions. Recent research and development of C-MFECs have indicated their potential applications in fuel cells, metal-air batteries, and hydrogen generation through water oxidation as well as electrochemical production of various commodity chemicals, such as ammonia, alcohols, hydrogen peroxide, and other useful hydrocarbons. Further research and development of C-MFECs would surely revolutionize traditional energy conversion and storage technologies with minimal environmental impact. In this short review article, we summarize the journey of C-MFECs over the past 10 years with an emphasis on materials development and their structure-property characterization for applications in fuel cells and metal-air batteries. Current challenges and future prospects of this emerging field are also discussed. K E Y W O R D Scarbon, electrocatalysis, energy conversion, energy storage, metal-free electrocatalyst

Tailoring Hierarchically Porous Nitrogen‐, Sulfur‐Codoped Carbon for High‐Performance Supercapacitors and Oxygen Reduction

“…Meanwhile, graphitic‐N and oxidized‐N can also provide strong physicochemical interactions for enhanced oxygen adsorption. [ 38 ] Considering that sulfur contents in NS‐PCM‐1000 and NS‐a‐PCM‐1000 are almost identical, the significant increment of pyridinic‐N, graphitic‐N, and oxidized‐N in NS‐a‐PCM‐1000 compared to that in NS‐PCM‐1000 indicates that nitrogen doping may play a dominant role in the promotion of ORR reactivities. In order to further comprehend the ORR dynamic behavior of NS‐a‐PCM‐1000, rotating disk electrode LSV technique was conducted at different rotating speeds (Figure S7, Supporting Information).…”

Coupling PEDOT on Mesoporous Vanadium Nitride Arrays for Advanced Flexible All‐Solid‐State Supercapacitors

“…[18][19][20][21] However, metal oxides and metal sulfides show poor intrinsic electronic conductivity, and thereby lead to compromised power/energy performance. [22,23] Meanwhile, metal nitride, typically vanadium nitride (VN), has been demonstrated to realize both high energy/power density in view of its high electrical conductivity (1.67 × 10 6 S m −1 ), wide potential window (1.0-1.2 V), and superior electrochemical redox reactivity. [24] With the help of nanoscale design, various VN nanostructures (such as nanosheets, nanorods, nanowires, nanoflowers) have been explored and boosted electrochemical kinetics and utilization are verified in these systems due to larger surface area and increased active sites.…”

Hydrothermal Carbon/Carbon Nanotube Composites as Electrocatalysts for the Oxygen Reduction Reaction

“…Currently, the most efficient electrocatalyst towards the ORR is based on platinum [3,4], which is a scarce and expensive noble metal that extremely pushes up the cost of the fuel cell [5]. Consequently, extensive research efforts have been made to develop non-noble metal catalysts, or metal-free catalysts, exhibiting good catalytic activity towards ORR and excellent durability [1,3,4,[6][7][8].…”

“…These modifications can be achieved by the incorporation of heteroatoms like nitrogen, sulfur, phosphorus, or boron and/or advanced carbon materials like graphene oxide or carbon nanotubes (CNTs) [9,12,13,17,[25][26][27][28]. Nitrogen is the most promising heteroatom for ORR, as pyridinic nitrogen favors the bonding of oxygen to the adjacent carbon, while the presence of quaternary nitrogen favors oxygen dissociation [7,29]. Therefore, the appropriate nitrogen functionalities seem to be essential to improve the electroactivity of the carbon materials towards the ORR.…”