Metal-Free Thiophene-Sulfur Covalent Organic Frameworks: Precise and Controllable Synthesis of Catalytic Active Sites for Oxygen Reduction

2020 ◽  
Vol 142 (18) ◽  
pp. 8104-8108 ◽  
Author(s):  
Daohao Li ◽  
Cuiyan Li ◽  
Lijie Zhang ◽  
Hui Li ◽  
Liangkui Zhu ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Covalent Organic Frameworks ◽  
Controllable Synthesis ◽  
Metal Free ◽  
Catalytic Active Sites

N-doped hierarchical porous metal-free catalysts derived from covalent triazine frameworks for the efficient oxygen reduction reaction

2019 ◽  
Vol 9 (23) ◽  
pp. 6606-6612 ◽  
Author(s):  
Yaqi Cao ◽  
Yuanzhi Zhu ◽  
Xifan Chen ◽  
Bahreselam Sielu Abraha ◽  
Wenchao Peng ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Oxygen Reduction Reaction ◽  
Oxygen Diffusion ◽  
Active Sites ◽  
Porous Metal ◽  
Reduction Reaction ◽  
Metal Free ◽  
Hierarchical Porous ◽  
The Hierarchical Structure ◽  
Catalytic Active Sites

The hierarchical structure enhances oxygen diffusion, improves electron transfer, and exposes more catalytic active sites for the ORR.

scholarly journals Covalent organic frameworks in Lieb lattice for tunable photocatalytic water splitting under visible light

2021 ◽  
Author(s):  
Hongde Yu ◽  
Dong Wang
Keyword(s):  
Hydrogen Production ◽  
Water Splitting ◽  
Active Sites ◽  
Rational Design ◽  
Near Infrared ◽  
Band Alignment ◽  
Covalent Organic Frameworks ◽  
Photocatalytic Water Splitting ◽  
Metal Free ◽  
Lieb Lattice

Covalent organic frameworks (COFs) with highly designable skeleton and inherent pores have emerged as promising organic photocatalysts for hydrogen production. However, inefficient solar light harvesting, strong excitonic effect, and the lack of active sites still pose major challenges to the rational design of COFs for efficient photocatalytic water splitting and the structure-property relationship has not been established. In this work, we investigated the fundamental mechanism of photoelectrochemical conversion in fully conjugated donor (D)-acceptor (A) COFs in Lieb lattice and proposed a facile strategy to achieve broad visible and near-infrared absorption, prompt exciton dissociation, tunable band alignment for overall water splitting, and metal-free catalysis of hydrogen production. Interestingly, we found that the exciton binding energy was substantially reduced with the narrowing of optical band gap and the increase of static dielectric constant. Further, we unraveled that the hydrogen bond played a vital role in suppressing the overpotential for hydrogen evolution reaction to enable metal-free catalysis. These findings not only highlight a novel route to modulating electronic properties of COFs towards high photocatalytic activity for water splitting, but also offer tremendous opportunities to design metal-free catalysts for other chemical transformations.

scholarly journals Identification of catalytic sites for oxygen reduction and oxygen evolution in N-doped graphene materials: Development of highly efficient metal-free bifunctional electrocatalyst

2016 ◽  
Vol 2 (4) ◽  
pp. e1501122 ◽  
Author(s):  
Hong Bin Yang ◽  
Jianwei Miao ◽  
Sung-Fu Hung ◽  
Jiazang Chen ◽  
Hua Bing Tao ◽  
...  
Keyword(s):  
Energy Conversion ◽  
Oxygen Reduction ◽  
Oxygen Evolution ◽  
Active Sites ◽  
Carbon Nanomaterials ◽  
Specific Capacity ◽  
Open Circuit ◽  
Practical Significance ◽  
Metal Free ◽  
Highly Efficient

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are critical to renewable energy conversion and storage technologies. Heteroatom-doped carbon nanomaterials have been reported to be efficient metal-free electrocatalysts for ORR in fuel cells for energy conversion, as well as ORR and OER in metal-air batteries for energy storage. We reported that metal-free three-dimensional (3D) graphene nanoribbon networks (N-GRW) doped with nitrogen exhibited superb bifunctional electrocatalytic activities for both ORR and OER, with an excellent stability in alkaline electrolytes (for example, KOH). For the first time, it was experimentally demonstrated that the electron-donating quaternary N sites were responsible for ORR, whereas the electron-withdrawing pyridinic N moieties in N-GRW served as active sites for OER. The unique 3D nanoarchitecture provided a high density of the ORR and OER active sites and facilitated the electrolyte and electron transports. As a result, the as-prepared N-GRW holds great potential as a low-cost, highly efficient air cathode in rechargeable metal-air batteries. Rechargeable zinc-air batteries with the N-GRW air electrode in a two-electrode configuration exhibited an open-circuit voltage of 1.46 V, a specific capacity of 873 mAh g−1, and a peak power density of 65 mW cm−2, which could be continuously charged and discharged with an excellent cycling stability. Our work should open up new avenues for the development of various carbon-based metal-free bifunctional electrocatalysts of practical significance.

Facile potentiostatic preparation of functionalized polyterthiophene-anchored graphene oxide as a metal-free electrocatalyst for the oxygen reduction reaction

2015 ◽  
Vol 3 (10) ◽  
pp. 5426-5433 ◽  
Author(s):  
M. Halappa Naveen ◽  
Hui-Bog Noh ◽  
Md Shahriar Al Hossain ◽  
Jung Ho Kim ◽  
Yoon-Bo Shim
Keyword(s):  
Graphene Oxide ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Sites ◽  
Reduction Reaction ◽  
Metal Free

A new polyterthiophene-anchored GO electrocatalyst was prepared. The C–N bonds of the polymer served as active sites for the ORR catalyst.

Template-free synthesis of polyacrylonitrile-derived porous carbon nanoballs on graphene for efficient oxygen reduction in zinc–air batteries

2021 ◽  
Vol 9 (15) ◽  
pp. 9644-9654
Author(s):  
Halima Begum ◽  
Mohammad Shamsuddin Ahmed ◽  
Seunghun Jung
Keyword(s):  
Fuel Cells ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Porous Carbon ◽  
Active Sites ◽  
Reduction Reaction ◽  
Metal Free ◽  
Template Free ◽  
Energy Conversion Devices ◽  
Zinc Air Batteries

Introducing abundant active sites and improving their activity are two critical considerations for designing metal-free nitrogenous electrocatalysts for the oxygen reduction reaction (ORR) in energy conversion devices such as metal–air batteries and fuel cells.

scholarly journals Fe-doped mayenite electride composite with 2D reduced Graphene Oxide: As a non-platinum based, highly durable electrocatalyst for Oxygen Reduction Reaction

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Karim Khan ◽  
Ayesha Khan Tareen ◽  
Muhammad Aslam ◽  
Sayed Ali Khan ◽  
Qasim khan ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Reduced Graphene Oxide ◽  
Precious Metal ◽  
Active Sites ◽  
Reduction Reaction ◽  
Metal Free ◽  
Reduced Graphene ◽  
Iron Based

AbstractSince the last decades, non-precious metal catalysts (NPMC), especially iron based electrocatalysts show sufficient activity, potentially applicant in oxygen reduction reaction (ORR), however they only withstand considerable current densities at low operating potentials. On the other hand iron based electrocatalysts are not stable at elevated cathode potentials, which is essential for high energy competence, and its remains difficult to deal. Therefore, via this research a simple approach is demonstrated that allows synthesis of nanosize Fe-doped mayenite electride, [Ca24Al28O64]4+·(e−)4 (can also write as, C12A7−xFex:e−, where doping level, x = 1) (thereafter, Fe-doped C12A7:e−), consist of abundantly available elements with gram level powder material production, based on simple citrate sol-gel method. The maximum achieved conductivity of this first time synthesized Fe-doped C12A7:e− composite materials was 249 S/cm. Consequently, Fe-doped C12A7:e− composite is cost-effective, more active and highly durable precious-metal free electrocatalyst, with 1.03 V onset potential, 0.89 V (RHE) half-wave potential, and ~5.9 mA/cm2 current density, which is higher than benchmark 20% Pt/C (5.65 mA/cm2, and 0.84 V). The Fe-doped C12A7:e− has also higher selectivity for desired 4e− pathway, and more stable than 20 wt% Pt/C electrode with higher immunity towards methanol poisoning. Fe-doped C12A7:e− loses was almost zero of its original activity after passing 11 h compared to the absence of methanol case, indicates that to introduce methanol has almost negligible consequence for ORR performance, which makes it highly desirable, precious-metal free electrocatalyst in ORR. This is primarily described due to coexistence of Fe-doped C12A7:e− related active sites with reduced graphene oxide (rGO) with pyridinic-nitrogen, and their strong coupling consequence along their porous morphology textures. These textures assist rapid diffusion of molecules to catalyst active sites quickly. In real system maximum power densities reached to 243 and 275 mW/cm2 for Pt/C and Fe-doped C12A7:e− composite, respectively.

Exposed N and S Active Sites: An Indicator for Oxygen Reduction on Metal-Free Yam-Derived Porous Carbons

2017 ◽  
Vol 4 (12) ◽  
pp. 3156-3162 ◽  
Author(s):  
Hao Fan ◽  
Zhen Dong ◽  
Jianshe Zhao
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Porous Carbons ◽  
Metal Free

Identifying the Catalytic Active Sites in Heteroatom-Doped Graphene for the Oxygen Reduction Reaction

Fuel Cells ◽  
2016 ◽  
Vol 16 (5) ◽  
pp. 568-576 ◽  
Author(s):  
I. S. Flyagina ◽  
K. J. Hughes ◽  
D. C. Mielczarek ◽  
D. B. Ingham ◽  
M. Pourkashanian
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Sites ◽  
Reduction Reaction ◽  
Doped Graphene ◽  
Catalytic Active Sites
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