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Two experimental methods to estimate the electrochemically active surface area (EASA) of microelectrodes are investigated. One method is based on electrocapacitive measurements and depends significantly on the surface roughness as well as on other parameters. The other method is based on faradaic current measurements and depends on the geometric surface area. The experimental results are supplemented with numerical modeling of electrodes with different surface roughness. A systematic study reveals a strong influence of the scale and arrangement of the surface roughness, the measurement potential and the electrolyte concentration on the EASA of microelectrodes estimated from the electrocapacitive measurements. The results show that electrocapacitive measurements should not be used to estimate the faradaic EASA of microelectrodes with a non-negligible surface roughness.

Two experimental methods to estimate the electrochemically active surface area (EASA) of microelectrodes are investigated. One method is based on electrocapacitive measurements and depends significantly on the surface roughness as well as on other parameters. The other method is based on faradaic current measurements and depends on the geometric surface area. The experimental results are supplemented with numerical modeling of electrodes with different surface roughness. A systematic study reveals a strong influence of the scale and arrangement of the surface roughness, the measurement potential and the electrolyte concentration on the EASA of microelectrodes estimated from the electrocapacitive measurements. The results show that electrocapacitive measurements should not be used to estimate the faradaic EASA of microelectrodes with a non-negligible surface roughness.

We demonstrated an asymmetric aqueous supercapacitor made of p- and n-type conducting polymer electrodes. We used the high electron affinity (EA) n-type polymer poly(benzimidazobenzophenanthroline) (BBL) as the anode conducting material, and the low ionization potential (IP) p-type polar polythiophene p(g(4)2T-T) as the cathode material. EA(BBL) matches IPp(g42T-T), enabling the fabrication of all-organic asymmetric p/n-supercapacitors that function in aqueous electrolytes. The devices operate in a voltage window up to 1 V, yielding areal capacitances of 90 mF cm(-2) and specific capacitances of 33 F g(-1) as well as excellent cycling stability with almost 100% capacitance retention over 10 000 cycles., Funding Agencies|Swedish Research Council; Swedish Foundation for Strategic Research; Knut and Alice Wallenberg Foundation; AForsk; VINNOVA; Swedish Government Strategic Research Area in Materials Science on Functional Materials at LinkOping University [SFO-Mat-LiU 2009 00971]; Finnish Cultural Foundation

A recently developed water-soluble self-doped sodium salt of bis[3,4-ethylenedioxythiophene] 3thiophene butyric acid (ETE-S) is electropolymerized and characterized by means of spectroelectrochemistry, electron paramagnetic resonance spectroscopy, and cyclic voltammetry, combined with the density functional theory (DFT) and time-dependent DFT calculations. The focus of the studies is to underline the nature of the charge carriers when the electrochemically polymerized ETE-S films undergo a reversible transition from reduced to electrically conductive oxidized states. Spectroelectrochemistry shows clear distinctions between absorption features from reduced and charged species. In the reduced state, the absorption spectrum of ETE-S electropolymerized film shows a peak that is attributed to HOMO. LUMO transition. As the oxidation level increases, this peak diminishes and the absorption of the film is dominated by spinless bipolaronic states with some admixture of polaronic states possessing a magnetic momentum. For fully oxidized samples, the bipolaronic states fully dominate, and the features in the absorption spectra are related to the drastic changes of the band structure, exhibiting a strong decrease of the band gap when a polymeric film undergoes oxidation., Funding Agencies|The Swedish Energy Agency [38332-1]; Norrkopings fond for Forskning och Utveckling, Carl Tryggers Stiftelse for Vetenskaplig Forskning [CTS: 13527]; CeNano (Linkoping University); Knut and Alice Wallenberg foundation (Tail of the Sun); Swedish Foundation for Strategic Research (SSF); Advanced Functional Material SFO-center at the Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Marie Sklodowska Curie Individual Fellowship (MSCA-IF-EF-ST); Marie Sklodowska Curie Individual Fellowship (Trans-Plant); Marie Sklodowska Curie Individual Fellowship [702641]

Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) is the most studied and explored mixed ion-electron conducting polymer system. PEDOT: PSS is commonly included as an electroactive conductor in various organic devices, e.g., supercapacitors, displays, transistors, and energy-converters. In spite of its long-term use as a material for storage and transport of charges, the fundamentals of its bulk capacitance remain poorly understood. Generally, charge storage in supercapacitors is due to formation of electrical double layers or redox reactions, and it is widely accepted that PEDOT: PSS belongs to the latter category. Herein, experimental evidence and theoretical modeling results are reported that significantly depart from this commonly accepted picture. By applying a two-phase, 2D modeling approach it is demonstrated that the major contribution to the capacitance of the two-phase PEDOT: PSS originates from electrical double layers formed along the interfaces between nanoscaled PEDOT-rich and PSS-rich interconnected grains that comprises two phases of the bulk of PEDOT: PSS. This new insight paves a way for designing materials and devices, based on mixed ion-electron conductors, with improved performance., Funding Agencies|The Swedish Energy Agency [38332-1]; Swedish Research Council [245-2010-1062]; Research Centre Security Link [VINNOVA 2009-00966]; Norrkopings fond for Forskning och Utveckling; CeNano; Knut and Alice Wallenberg Foundation; Swedish Foundation for Strategic Research (SSF); Advanced Functional Material SFO-center at Linkoping University [2009-00971]; Swedish National Infrastructure for Computing (SNIC); European Research Council (ERC) [307596, 681881]; Knut and Alice Wallenberg Foundation (Tail of the Sun); Swedish Foundation for Strategic Research [0-3D]

Nonradiative decay of plasmons in metallic nanostructures offers unique means for light-to-heat conversion at the nanoscale. Typical thermoplasmonic systems utilize discrete particles, while metal nanohole arrays were instead considered suitable as heat sinks to reduce heating effects. By contrast, we show for the first time that under uniform broadband illumination (e.g., the sun) ultrathin plasmonic nanohole arrays can be highly competitive plasmonic heaters and provide significantly higher temperatures than analogous nanodisk arrays. Our plasmonic nanohole arrays also heat significantly more than nonstructured metal films, while simultaneously providing superior light transmission. Besides being efficient light-driven heat sources, these thin perforated gold films can simultaneously be used as electrodes. We used this feature to develop "plasmonic thermistors" for electrical monitoring of plasmon-induced temperature changes. The nanohole arrays provided temperature changes up to 7.5 K by simulated sunlight, which is very high compared to previously reported plasmonic systems under similar conditions (solar illumination and ambient conditions). Both temperatures and heating profiles quantitatively agree with combined optical and thermal simulations. Finally, we demonstrate the use of a thermoplasmonic nanohole electrode to power the first hybrid plasmonic ionic thermoelectric device, resulting in strong solar-induced heat gradients and corresponding thermoelectric voltages., Funding Agencies|Wenner-Gren Foundations; Swedish Research Council; Swedish Foundation for Strategic Research; AForsk Foundation; Knut and Alice Wallenberg Foundation; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU No 2009 00971]

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is the most studied and explored mixed ion-electron conducting polymer system. PEDOT:PSS is commonly included as an electroactive conductor in various organic devices, e.g., supercapacitors, displays, transistors, and energy-converters. In spite of its long-term use as a material for storage and transport of charges, the fundamentals of its bulk capacitance remain poorly understood. Generally, charge storage in supercapacitors is due to formation of electrical double layers or redox reactions, and it is widely accepted that PEDOT:PSS belongs to the latter category. Herein, experimental evidence and theoretical modeling results are reported that significantly depart from this commonly accepted picture. By applying a two-phase, 2D modeling approach it is demonstrated that the major contribution to the capacitance of the two-phase PEDOT:PSS originates from electrical double layers formed along the interfaces between nanoscaled PEDOT-rich and PSS-rich interconnected grains that comprises two phases of the bulk of PEDOT:PSS. This new insight paves a way for designing materials and devices, based on mixed ion-electron conductors, with improved performance.

El presente trabajo trata sobre el diseño de una máquina compactadora que, mediante la presión que se crea entre dos rodillos giratorios, compacta cierto producto en estado de polvo para conseguir briquetas sólidas. El proceso de compactación permite transformar el producto en polvo a piezas sólidas (briquetas) para facilitar su manipulación, transporte, almacenamiento y, en caso de residuos, su reciclaje. La intención del proyecto es diseñar una máquina briquetadora basada en las opciones existentes en el mercado e intentar juntar las ventajas eliminando los inconvenientes de los diferentes fabricantes. También era aconsejable usar el mayor número de piezas normalizadas, en la medida de lo posible, en el diseño para simplificar el proceso y reducir costes. Para alcanzar las metas propuestas se ha establecido contacto con una empresa que usa máquinas semejantes y se ha realizado el estudio del funcionamiento de ésta. Más adelante ha sido posible contactar con el ingeniero que diseñó la máquina nombrada para familiarizarse más con el proceso de diseño de máquinas y ver en primera persona el trabjo que realiza en realidad un ingeniero. Finalmente, con algunas complicaciones, la máquina resultó satisfactoria y cumplió con los requisitos establecidos. Conseguimos resistencia suficiente de la estructura para resistir las elevadas fuerzas de compactación que se generan en el interior de la máquina junto con la producción elevada de briquetas. En conclusión, el objetivo principal se ha cumplido, a pesar de algunas dificultades que se han presentado a lo largo de la realización del proyecto. Se han tenido que eliminar ciertos contenidos que eran interesantes de desarrollar y en algunas ocasiones se han tomado decisiones algo específicas y poco comunes. Se ha reducido al máximo el número de piezas que requieren cierto elaboración y mecanizado, y se ha intentado hacer el diseño con el máximo de elementos normalizados para que la máquina resulte ser lo más simple posible.