Nitrogen‐Coordinated Single Cobalt Atom Catalysts for Oxygen Reduction in Proton Exchange Membrane Fuel Cells

Abstract

Due to the Fenton reaction, the presence of Fe and peroxide in electrodes generates free radicals causing serious degradation of the organic ionomer and the membrane. Pt-free and Fe-free cathode catalysts therefore are urgently needed for durable and inexpensive proton exchange membrane fuel cells (PEMFCs). Herein, a high-performance nitrogen-coordinated single Co atom catalyst is derived from Co-doped metal-organic frameworks (MOFs) through a one-step thermal activation. Aberration-corrected electron microscopy combined with X-ray absorption spectroscopy virtually verifies the CoN coordination at an atomic level in the catalysts. Through investigating effects of Co doping contents and thermal activation temperature, an atomically Co site dispersed catalyst with optimal chemical and structural properties has achieved respectable activity and stability for the oxygen reduction reaction (ORR) in challenging acidic media (e.g., half-wave potential of 0.80 V vs reversible hydrogen electrode (RHE). The performance is comparable to Fe-based catalysts and 60 mV lower than Pt/C -60 μg Pt cm ). Fuel cell tests confirm that catalyst activity and stability can translate to high-performance cathodes in PEMFCs. The remarkably enhanced ORR performance is attributed to the presence of well-dispersed CoN active sites embedded in 3D porous MOF-derived carbon particles, omitting any inactive Co aggregates.

Boosting the Loading of Metal Single Atoms via a Bioconcentration Strategy

“…As shown by the HAADF‐STEM images and EDX mapping results, the Co, Ni, and Mn single atoms with high concentration were uniformly distributed on the HCF (Figure 4b–d,g–i,l–n). The binding energies of Co, Ni, and Mn in XPS spectra were similar with those of the previously reported Co‐N‐C, Ni‐N‐C, and Mn‐N‐C single atoms (Figure 4e,j,o), respectively . Determined by the XPS results, the mass percentage of Co, Ni, and Mn single atoms were calculated to be 3.7%, 4.2%, and 2.6%, respectively (Figure S16 and Table S4, Supporting Information).…”

The Multifaceted Reactivity of Single‐Atom Heterogeneous Catalysts

“…[28,54,121] However,s urpassing the efficiencyo fP t/C is challenging since the reaction proceeds by a2e À pathway and produces less electricity than the alternative 4e À pathway.On the other hand, this presents an efficient route for the H 2 O 2 synthesis,i nw hich case higher selectivity is expected upon complete elimination of NPs and clusters.T he improved performance of aPt 1 /TiC catalyst than Pt 1 /TiN indicated that the support can strongly influence the performance. [122][123][124][125][126][127] Interesting prospects to tune the mechanism have been reported in the oxidations of methanol, ethanol, and formic acid. [122][123][124][125][126][127] Interesting prospects to tune the mechanism have been reported in the oxidations of methanol, ethanol, and formic acid.…”

Ultrathin Nitrogen‐Doped Holey Carbon@Graphene Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions in Alkaline and Acidic Media

“…Figure 3d displays an obvious OER activity (E OER10 = 1.58 V), almost identical to that of Ir/C (1.56 V). [23] N-HC@G-900 shows lower acidic stability than Ir/C (Figure 3e), but better than other reported metal-free electrocatalysts. [23] N-HC@G-900 shows lower acidic stability than Ir/C (Figure 3e), but better than other reported metal-free electrocatalysts.…”