Quasi-Double-Star Nickel and Iron Active Sites for High-Efficient Carbon Dioxide Electroreduction

2021 ◽  
Author(s):  
Ting Zhang ◽  
Xu Han ◽  
Hong Liu ◽  
Martí Biset-Peiró ◽  
Xuan Zhang ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Active Sites ◽  
Double Star ◽  
Single Atom ◽  
Practical Application ◽  
High Efficient ◽  
Iron Active Sites ◽  
Carbon Dioxide Electroreduction

Although the Faraday efficiencies (FEs) obtained on most of the Ni based single-atom catalysts (Ni-N-C) are satisfactory (generally > 90 %) for electrochemical transfer CO2 to CO, the practical application...

Electrochemical reduction of carbon dioxide with nearly 100% carbon monoxide faradaic efficiency from vacancy-stabilized single-atom active sites

2021 ◽  
Author(s):  
Chenbao Lu ◽  
Kaiyue Jiang ◽  
Diana Tranca ◽  
Ning Wang ◽  
Hui Zhu ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Energy Conversion ◽  
Electrochemical Reduction ◽  
Active Sites ◽  
Co2 Reduction ◽  
Reduction Reaction ◽  
Single Atom ◽  
Faradaic Efficiency ◽  
Co2 Reduction Reaction

Single-atom catalysts (SACs) have been rapidly rising as emerging materials in the field of energy conversion, especially for CO2 reduction reaction. However, the selectivity and running current are still beyond...

A Pyridinic Fe-N4 Macrocycle Effectively Models the Active Sites in Fe/N-Doped Carbon Electrocatalysts

2020 ◽  
Author(s):  
Travis Marshall-Roth ◽  
Nicole J. Libretto ◽  
Alexandra T. Wrobel ◽  
Kevin Anderton ◽  
Nathan D. Ricke ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Catalytic Properties ◽  
Reduction Reaction ◽  
Iron Phthalocyanine ◽  
Electrochemical Studies ◽  
Onset Potential ◽  
Nitrogen Doped Carbon ◽  
Iron Active Sites

Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum in fuel cells, but their active site structures are poorly understood. A leading postulate is that iron active sites in this class of materials exist in an Fe-N<sub>4</sub> pyridinic ligation environment. Yet, molecular Fe-based catalysts for the oxygen reduction reaction (ORR) generally feature pyrrolic coordination and pyridinic Fe-N<sub>4</sub> catalysts are, to the best of our knowledge, non-existent. We report the synthesis and characterization of a molecular pyridinic hexaazacyclophane macrocycle, (phen<sub>2</sub>N<sub>2</sub>)Fe, and compare its spectroscopic, electrochemical, and catalytic properties for oxygen reduction to a prototypical Fe-N-C material, as well as iron phthalocyanine, (Pc)Fe, and iron octaethylporphyrin, (OEP)Fe, prototypical pyrrolic iron macrocycles. N 1s XPS signatures for coordinated N atoms in (phen<sub>2</sub>N<sub>2</sub>)Fe are positively shifted relative to (Pc)Fe and (OEP)Fe, and overlay with those of Fe-N-C. Likewise, spectroscopic XAS signatures of (phen<sub>2</sub>N<sub>2</sub>)Fe are distinct from those of both (Pc)Fe and (OEP)Fe, and are remarkably similar to those of Fe-N-C with compressed Fe–N bond lengths of 1.97 Å in (phen<sub>2</sub>N<sub>2</sub>)Fe that are close to the average 1.94 Å length in Fe-N-C. Electrochemical studies establish that both (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe have relatively high Fe(III/II) potentials at ~0.6 V, ~300 mV positive of (OEP)Fe. The ORR onset potential is found to directly correlate with the Fe(III/II) potential leading to a ~300 mV positive shift in the onset of ORR for (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe relative to (OEP)Fe. Consequently, the ORR onset for (phen<sub>2</sub>N<sub>2</sub>)Fe and (Pc)Fe is within 150 mV of Fe-N-C. Unlike (OEP)Fe and (Pc)Fe, (phen<sub>2</sub>N<sub>2</sub>)Fe displays excellent selectivity for 4-electron ORR with <4% maximum H<sub>2</sub>O<sub>2</sub> production, comparable to Fe-N-C materials. The aggregate spectroscopic and electrochemical data establish (phen<sub>2</sub>N<sub>2</sub>)Fe as a pyridinic iron macrocycle that effectively models Fe-N-C active sites, thereby providing a rich molecular platform for understanding this important class of catalytic materials.<p><b></b></p>

Graphdiyne Anchored Ultrafine Ag Nanoparticles for High Efficient and Solvent-Free Catalysis of CO2 Cycloaddition

2021 ◽  
Author(s):  
Chang Liu ◽  
Chao Zhang ◽  
Tongbu Lu
Keyword(s):  
Ag Nanoparticles ◽  
Co2 Reduction ◽  
Value Added ◽  
Solvent Free ◽  
Alternative Route ◽  
Practical Application ◽  
Co2 Utilization ◽  
High Efficient

Apart from photo-/electro-catalytic CO2 reduction, an important alternative route to CO2 utilization is to use this inert molecule as a C1 source to synthesize value-added chemicals, while the practical application...

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