Sol–gel chemistry in molten Brønsted acids towards “activated” carbons and beyond

Koyutürk, Burak; Evans, J. K.; Multhaupt, Hendrik; Selve, Sören; Simke, Jan Ron Justin; Wark, Michael; Fellinger, Tim‐Patrick

doi:10.1039/c9nr01722d

Cited by 3 publications

(2 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…P atoms might also be incorporated into the graphitic carbon network. Phosphorus compounds can additionally be encapsulated by the carbon as the H 3 PO 4 activation is a sol–gel-type carbonization . However, it is also reported that substitution of C by P atoms is rather uncommon as the π conjugation with a graphene plane is not coplanar. , Therefore, the bonded forms (−C–P and C–O–P) seem to be more likely present in the activated biomass.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Activation of Biomass. Activation of coconut shells and rye straw was adapted from Koyuturk et al 30 Three hundred milligrams of coconut shell powder (COCONIT 300, Mahlwerk Neubauer-Friedrich Geffers) or minced rye straw was impregnated with 1.5 g of H 3 PO 4 (≤85% Carl Roth, p.a.). After two days of drying in a vacuum oven at 30 °C, the impregnated biomass was heated up to 580 °C with 5 °C min −1 and held for 3 h under a nitrogen flow of 100 mL min −1 in a steal tube furnace followed by a washing step with 0.5 M HCl (VWR, p.a.)…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Incorporation of Activated Biomasses in Fe-N-C Catalysts for Oxygen Reduction Reaction with Enhanced Stability in Acidic Media

Müller-Hülstede

Schonvogel

Schmies

et al. 2021

ACS Appl. Energy Mater.

Self Cite

View full text Add to dashboard Cite

Fe-N-C materials are promising oxygen reduction reaction (ORR) catalysts for replacing expensive platinum-based catalysts (Pt/C) in proton exchange membrane fuel cells. However, they still show low volumetric activity and stability compared to Pt/C catalysts, with carbon corrosion being one of the main factors for the loss of active Fe-N x sites. Within this study, phosphoric acid-activated rye straw and coconut shells are revealed as a promising matrix for Fe-N x sites with advanced stability against electrochemical carbon corrosion (5000 cycles, 1.0–1.5 VRHE, and 0.1 M HClO4) compared to a common Fe-N-C catalyst based on carbon black. Electrochemical characterization of the two biomass-based catalysts (Fe-N-CBio) shows on the one hand 50% higher stability in terms of mass activity as well as comparable activity and active site density but on the other hand a lower selectivity toward the four-electron ORR than the common Fe-N-C catalyst. Nitrite stripping experiments in acetate buffer as an electrolyte display a 1.5-fold stronger effect of carboxylic acid adsorption than on a common Fe-N-C catalyst, revealing differences to the electronic structure of the Fe-N-CBio catalyst. This difference is mainly attributed to the presence of phosphor species and higher amounts of nitrogen functionalities in the Fe-N-CBio catalysts. The presence of P is assumed to stabilize the carbon against carbon corrosion by inhibiting electron withdrawal from the C. This study points out the impact factors on Fe-N-C stability and further shows the promising application of activated biomasses in more stable and sustainable Fe-N-C catalysts for ORR.

show abstract

Section: Results and Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Incorporation of Activated Biomasses in Fe-N-C Catalysts for Oxygen Reduction Reaction with Enhanced Stability in Acidic Media

Müller-Hülstede

Schonvogel

Schmies

et al. 2021

ACS Appl. Energy Mater.

Self Cite

View full text Add to dashboard Cite

show abstract

High‐Loading, Well‐Dispersed Phosphorus Confined on Nanoporous Carbon Surfaces with Enhanced Catalytic Activity and Cyclic Stability

et al. 2021

View full text Add to dashboard Cite

Phosphorus‐doped carbon materials are promising alternatives to noble metal‐based catalysts for the highly selective oxidation of benzyl alcohol to benzaldehyde, but it is challenging to achieve high loadings of high‐activity P dopants in metal‐free catalysts. Here, the preparation of high‐loading and well‐dispersed P atoms confined to the surfaces of cellulose‐derived carbon via a dissolving‐doping strategy is reported. In this method, cellulose is dissolved in phosphoric acid to generate a cellulose‐phosphoric supramolecular collosol, which is then directly carbonized. The as‐prepared carbon possesses a high specific surface area of 1491 cm3 g−1 and a high P content of 8.8 wt%. The P‐doped nanoporous carbon shows a superior catalytic activity and cyclic stability toward benzyl alcohol oxidation, with a high turnover frequency of 3.5 × 10−3 mol g−1 h−1 and a low activation energy of 35.6 kJ mol−1. Experimental results and theoretical calculations demonstrate that the graphitic C3PO species is the leading catalytic active center in this material. This study provides a novel strategy to prepare P dopants in nanoporous carbon materials with excellent catalytic performance.

show abstract

Relevant Properties of Carbon Support Materials in Successful Fe-N-C Synthesis for the Oxygen Reduction Reaction: Study of Carbon Blacks and Biomass-Based Carbons

et al. 2020

Self Cite

View full text Add to dashboard Cite

Fe-N-C materials are promising non-precious metal catalysts for the oxygen reduction reaction in fuel cells and batteries. However, during the synthesis of these materials less active Fe-containing nanoparticles are formed in many cases which lead to a decrease in electrochemical activity and stability. In this study, we reveal the significant properties of the carbon support required for the successful incorporation of Fe-N-related active sites. The impact of two carbon blacks and two activated biomass-based carbons on the Fe-N-C synthesis is investigated and crucial support properties are identified. Carbon supports having low portions of amorphous carbon, moderate surface areas (>800 m2/g) and mesopores result in the successful incorporation of Fe and N on an atomic level and improved oxygen reduction reaction (ORR) activity. A low surface area and especially amorphous parts of the carbon promote the formation of metallic iron species covered by a graphitic layer. In contrast, highly microporous systems with amorphous carbon provoke the formation of less active iron carbides and carbon nanotubes. Overall, a phosphoric acid activated biomass is revealed as novel and sustainable carbon support for the formation of Fe-Nx sites. Overall, this study provides valuable and significant information for the future development of novel and sustainable carbon supports for Fe-N-C catalysts.

show abstract

Sol–gel chemistry in molten Brønsted acids towards “activated” carbons and beyond

Abstract: Chemical activation of carbons is usually assigned to an oxidative and dehydrating nature of activating agents. We herein suggest that activating agents rather act as high temperature solvents and the porosity is developed by carbon phase separation.

Cited by 3 publications

References 31 publications

Incorporation of Activated Biomasses in Fe-N-C Catalysts for Oxygen Reduction Reaction with Enhanced Stability in Acidic Media

Incorporation of Activated Biomasses in Fe-N-C Catalysts for Oxygen Reduction Reaction with Enhanced Stability in Acidic Media

High‐Loading, Well‐Dispersed Phosphorus Confined on Nanoporous Carbon Surfaces with Enhanced Catalytic Activity and Cyclic Stability

Relevant Properties of Carbon Support Materials in Successful Fe-N-C Synthesis for the Oxygen Reduction Reaction: Study of Carbon Blacks and Biomass-Based Carbons

Contact Info

Product

Resources

About