Conductive Carbon Materials from the Hydrothermal Carbonization of Vineyard Residues for the Application in Electrochemical Double-Layer Capacitors (EDLCs) and Direct Carbon Fuel Cells (DCFCs)

Abstract

This study investigates the production of bio-based carbon materials for energy storage and conversion devices based on two different vineyard residues (pruning, pomace) and cellulose as a model biomass. Three different char categories were produced via pyrolysis at 900 °C for 2 h (biochars, BC), hydrothermal carbonization (HTC) (at 220, 240 or 260 °C) with different reaction times (60, 120 or 300 min) (hydrochars, HC), or HTC plus pyrolysis (pyrolyzed hydrochars, PHC). Physicochemical, structural, and electrical properties of the chars were assessed by elemental and proximate analysis, gas adsorption surface analysis with N2 and CO2, compression ratio, bulk density, and electrical conductivity (EC) measurements. Thermogravimetric analysis allowed conclusions to be made about the thermochemical conversion processes. Taking into consideration the required material properties for the application in electrochemical double-layer capacitors (EDLC) or in a direct carbon fuel cell (DCFC), the suitability of the obtained materials for each application is discussed. Promising materials with surface areas up to 711 m2 g−1 and presence of microporosity have been produced. It is shown that HTC plus pyrolysis from cellulose and pruning leads to better properties regarding aromatic carbon structures, carbon content (>90 wt.%), EC (up to 179 S m−1), and porosity compared to one-step treatments, resulting in suitable materials for an EDLC application. The one-step pyrolysis process and the resulting chars with lower carbon contents and low EC values between 51 and 56 S m−1 are preferred for DCFC applications. To conclude, biomass potentials can be exploited by producing tailored biomass-derived carbon materials via different carbonization processes for a wide range of applications in the field of energy storage and conversion.

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“…The high temperature pyrolysis is generally the most common and important carbonization method [ 9 ]. Under limited oxygen supply or anoxic conditions and at a certain temperature (<700 °C), biomass resources can be carbonized into biochar, a carbon-rich, stable, and highly aromatic solid product [ 10 , 11 , 12 , 13 ].…”

Study of High Performance Sulfonated Polyether Ether Ketone Composite Electrolyte Membranes

“…This operation is not only more efficient but also more economically feasible. Therefore, many researchers are making large amounts of effort to find the best materials and processes to elevate the electrochemical performance of fuel cells for different applications [7,8,9,10].…”

Exceptional rate capability from carbon‐encapsulated polyaniline supercapacitor electrodes

“…However, as HTC is more electrically conductive than PANI the overall R s decreases. [ 61 ] Additionally, the gradient of CNT/PANI/HTC appears steeper than that of CNT/PANI, indicating faster diffusion kinetics of doping ions. This suggests the effect of the HTC layer is to promote the movement of ions and electrons throughout the network while slightly impeding the redox switching of PANI.…”