Ten years of carbon-based metal-free electrocatalysts

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.

Recent progress in carbon-based electrochemical catalysts:From structure design to potential applications

Advances in research and development of carbon-based metal-free electrocatalysts(C-MFECs)have provided potential alternatives to precious metal catalysts for various reactions important to renewable energy and environmental remediation.This timely but critical review provides an overview of recent breakthroughs(within the past 5 years or so)on C-MFECs in all aspects,including the design and regulation of intrinsic catalytic active sites,design and synthesis of carbon composite and hybrid carbon catalysts,mechanism understanding,and potential applications in clean energy storage and energy/chemical conversion.Current challenges and future opportunities in the field of metal-free carbon electrocatalysis are also discussed to provide forward-looking opportunities for their potential applications in various catalytic processes of practical significance.

Large-scale production of holey carbon nanosheets implanted with atomically dispersed Fe sites for boosting oxygen reduction electrocatalysis

Atomically dispersed metals stabilized by nitrogen elements in carbon skeleton hold great promise as alternatives for Pt-based catalysts towards oxygen reduction reaction in proton exchange membrane fuel cells.However,their widespread commercial applications are limited by complicated synthetic procedures for mass production.Herein,we are proposing a simple,green mechanochemical approach to synthesize zeolitic imidazolate frameworks precursors for the production of atomically dispersed“Fe-N_(4)”sites in holey carbon nanosheets on a large scale.The thin porous carbon nanosheets(PCNs)with atomically dispersed“Fe-N_(4)”moieties can be prepared in hectogram scale by directly pyrolysis of salt-sealed Fe-based zeolitic imidazolate framework-8(Fe-ZIF-8@NaCl)precursors.The PCNs possess large specific surface area,abundant lamellar edges and rich“Fe-N_(4)”active sites,and show superior catalytic activity towards oxygen reduction reaction in an acid electrolyte.This work provides a promising approach to cost-effective production of atomically dispersed transition metal catalysts on large scale for practical applications.