@article{YanJosefHuangetal.2019, author = {Yan, Runyu and Josef, Elinor and Huang, Haijian and Leus, Karen and Niederberger, Markus and Hofmann, Jan P. and Walczak, Ralf and Antonietti, Markus and Oschatz, Martin}, title = {Understanding the charge storage mechanism to achieve high capacity and fast ion storage in sodium-ion capacitor anodes by using electrospun nitrogen-doped carbon fibers}, series = {Advanced functional materials}, volume = {29}, journal = {Advanced functional materials}, number = {26}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1616-301X}, doi = {10.1002/adfm.201902858}, pages = {13}, year = {2019}, abstract = {Microporous nitrogen-rich carbon fibers (HAT-CNFs) are produced by electrospinning a mixture of hexaazatriphenylene-hexacarbonitrile (HAT-CN) and polyvinylpyrrolidone and subsequent thermal condensation. Bonding motives, electronic structure, content of nitrogen heteroatoms, porosity, and degree of carbon stacking can be controlled by the condensation temperature due to the use of the HAT-CN with predefined nitrogen binding motives. The HAT-CNFs show remarkable reversible capacities (395 mAh g(-1) at 0.1 A g(-1)) and rate capabilities (106 mAh g(-1) at 10 A g(-1)) as an anode material for sodium storage, resulting from the abundant heteroatoms, enhanced electrical conductivity, and rapid charge carrier transport in the nanoporous structure of the 1D fibers. HAT-CNFs also serve as a series of model compounds for the investigation of the contribution of sodium storage by intercalation and reversible binding on nitrogen sites at different rates. There is an increasing contribution of intercalation to the charge storage with increasing condensation temperature which becomes less active at high rates. A hybrid sodium-ion capacitor full cell combining HAT-CNF as the anode and salt-templated porous carbon as the cathode provides remarkable performance in the voltage range of 0.5-4.0 V (95 Wh kg(-1) at 0.19 kW kg(-1) and 18 Wh kg(-1) at 13 kW kg(-1)).}, language = {en} } @article{LaiFengHeietal.2019, author = {Lai, Feili and Feng, Jianrui and Hei, Tobias and Wang, Gui-Chang and Adler, Peter and Antonietti, Markus and Oschatz, Martin}, title = {Strong metal oxide-support interactions in carbon/hematite nanohybrids activate novel energy storage modes for ionic liquid-based supercapacitors}, series = {Energy Storage Materials}, volume = {20}, journal = {Energy Storage Materials}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2405-8297}, doi = {10.1016/j.ensm.2019.04.035}, pages = {188 -- 195}, year = {2019}, abstract = {Strong metal oxide-support interaction is crucial to activate high energy storage modes of carbon-supported hybrid electrodes in ionic liquid-based supercapacitors. Although it is known that conductive supports can influence the electrochemical properties of metal oxides, insights into how metal oxide-support interactions can be exploited to optimize joint energy storage properties are lacking. We report the junction between alpha-Fe2O3 nanosplotches and phosphorus-doped ordered mesoporous carbon (CMK-3-P) with strong covalent anchoring of the metal oxide. The oxide-carbon interaction in CMK-3-P-Fe2O3 is strengthening the junction and charge transfer between Fe2O3 and CMK-3-P. It enhances energy storage by intensifying the interaction between ionic liquid ions and the surface of the electrode. Density functional theory simulations reveal that the strong metal oxide-support interaction increases the adsorption energy of ionic liquid to -4.77 eV as compared to -3.85 eV for a CMK-3Fe(2)O(3) hybrid with weaker binding. In spite of the lower specific surface area and apparently similar energy storage mode, the CMK-3-P-Fe2O3 exhibits superior electrical double-layer capacitor performance with a specific capacitance of 179 F g(-1) at 2 mV s(-1) (0-3.5 V) in comparison to Fe2O3-free CMK-3 and CMK-3-P reference materials. This principle for design of hybrid electrodes can be applicable for future rational design of stable metal oxide-support electrodes for advanced energy storage.}, language = {en} } @article{WalczakSavateevHeskeetal.2019, author = {Walczak, Ralf and Savateev, Aleksandr and Heske, Julian and Tarakina, Nadezda V. and Sahoo, Sudhir and Epping, Jan D. and Kuehne, Thomas D. and Kurpil, Bogdan and Antonietti, Markus and Oschatz, Martin}, title = {Controlling the strength of interaction between carbon dioxide and nitrogen-rich carbon materials by molecular design}, series = {Sustainable energy \& fuels}, volume = {3}, journal = {Sustainable energy \& fuels}, number = {10}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2398-4902}, doi = {10.1039/c9se00486f}, pages = {2819 -- 2827}, year = {2019}, abstract = {Thermal treatment of hexaazatriphenylene-hexacarbonitrile (HAT-CN) in the temperature range from 500 degrees C to 700 degrees C leads to precise control over the degree of condensation, and thus atomic construction and porosity of the resulting C2N-type materials. Depending on the condensation temperature of HAT-CN, nitrogen contents of more than 30 at\% can be reached. In general, these carbons show adsorption properties which are comparable to those known for zeolites but their pore size can be adjusted over a wider range. At condensation temperatures of 525 degrees C and below, the uptake of nitrogen gas remains negligible due to size exclusion, but the internal pores are large and polarizing enough that CO2 can still adsorb on part of the internal surface. This leads to surprisingly high CO2 adsorption capacities and isosteric heat of adsorption of up to 52 kJ mol(-1). Theoretical calculations show that this high binding enthalpy arises from collective stabilization effects from the nitrogen atoms in the C2N layers surrounding the carbon atom in the CO2 molecule and from the electron acceptor properties of the carbon atoms from C2N which are in close proximity to the oxygen atoms in CO2. A true CO2 molecular sieving effect is achieved for the first time in such a metal-free organic material with zeolite-like properties, showing an IAST CO2/N-2 selectivity of up to 121 at 298 K and a N-2/CO2 ratio of 90/10 without notable changes in the CO2 adsorption properities over 80 cycles.}, language = {en} } @article{QinHeilSchmidtetal.2019, author = {Qin, Qing and Heil, T. and Schmidt, J. and Schmallegger, Max and Gescheidt, Georg and Antonietti, Markus and Oschatz, Martin}, title = {Electrochemical Fixation of Nitrogen and Its Coupling with Biomass Valorization with a Strongly Adsorbing and Defect Optimized Boron-Carbon-Nitrogen Catalyst}, series = {ACS Applied Energy Materials}, volume = {2}, journal = {ACS Applied Energy Materials}, number = {11}, publisher = {American Chemical Society}, address = {Washington}, issn = {2574-0962}, doi = {10.1021/acsaem.9b01852}, pages = {8359 -- 8365}, year = {2019}, abstract = {The electrochemical conversion of low-cost precursors into high-value chemicals using renewably generated electricity is a promising approach to build up an environmentally friendly energy cycle, including a storage element. The large-scale implementation of such process can, however, only be realized by the design of cost-effective electrocatalysts with high efficiency and highest stability. Here, we report the synthesis of N and B codoped porous carbons. The constructed B-N motives combine abundant unpaired electrons and frustrated Lewis pairs (FLPs). They result in desirable performance for electrochemical N-2 reduction reaction (NRR) and electrooxidation of 5-hydroxymethylfurfural (HMF) in the absence of any metal cocatalyst. A maximum Faradaic efficiency of 15.2\% with a stable NH3 production rate of 21.3 mu g h(-1) mg(-1) is obtained in NRR. Besides, 2,5-furandicarboxylic acid (FDCA) is first obtained by using non-metalbased electrocatalysts at a conversion of 71\% and with yield of 57\%. Gas adsorption experiments elucidate the relationship between the structure and the ability of the catalysts to activate the substrate molecules. This work opens up deep insights for the rational design of non-metal-based catalysts for potential electrocatalytic applications and the possible enhancement of their activity by the introduction of FLPs and point defects at grain boundaries.}, language = {en} }