Robust Co‐Embedded Nitrogen Doped Carbon Catalyst for Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cell

Abstract

This work reports non‐noble, cobalt embedded nitrogen doped carbon (CoNC) catalysts for oxygen reduction reaction (ORR) in Nafion‐based acidic proton exchange membrane fuel cells (PEMFCs). CoNC catalysts are synthesized through direct pyrolysis of two different zeolitic imidazolate framework (ZIF) precursors, Zn‐ZIF and Co‐ZIF. Profiting from two different precursor approach, appropriate assimilation of metal, nitrogen and carbon components is achieved which boosts oxygen reduction. Electrochemical results exemplified CoNC 3–1 catalyst derived from Zn‐ZIF:Co‐ZIF precursor in the weight ratio of 3 : 1 as the better ORR catalyst. CoNC 3–1 catalyst exhibited the highest electrochemical surface area (ECSA) (570 cm2), highest limiting current density (‐5.14 mA cm−2) and followed near 4e− reduction of oxygen revealing superior ORR activity. The catalyst also demonstrated remarkable durability with loss of only 6 % of ECSA after 30,000 cycles of accelerated durability test. The enhanced ORR activity and durability is attributed to optimal balance of Co−Nx active sites along with appropriate N contents and graphitic carbon framework.

Recent Progress in ZIF‐Derived Carbons for Enhanced Oxygen Reduction Reaction Electrocatalysis

“…The acid etching treatment is supposed to eliminate unreactive metal oxides and other impurities that may form on the surface of the catalysts during the pyrolysis process. [106][107] Acid etching can also improve the surface roughness and porosity of the catalysts, which facilitates the formation of an internally connected hierarchical porous structure, thus increasing the specific surface area and optimizing the porosity of the material (Figure 6). Moreover, acid etching treatments yield more defect sites, enriching the material's defect structure, which in turn provides additional catalytic sites for O 2 adsorption, thereby promoting the ORR process.…”

“…Some common acids used for etching are hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and acetic acid. The acid etching treatment is supposed to eliminate unreactive metal oxides and other impurities that may form on the surface of the catalysts during the pyrolysis process [106–107] . Acid etching can also improve the surface roughness and porosity of the catalysts, which facilitates the formation of an internally connected hierarchical porous structure, thus increasing the specific surface area and optimizing the porosity of the material (Figure 6).…”

An electron “donor–acceptor–donor” strategy to activate ZIF-67 as a cathode material for fuel cells and zinc ion hybrid supercapacitor

“…Among them MOFs have shown interesting prospects for a variety of applications because of their chemical flexibility, high surface area and topological control. 2,6 As a subclass of MOFs, zeolite imidazolate frameworks (ZIFs) provide a new platform for energy conversion and storage together with their traditional applications in various fields such as gas adsorption, catalysis, and sensors. 7,8 The ZIFs have been used as a standard precursor to synthesize an in situ heteroatom doped carbon network via a pyrolysis process.…”