Researchers at NETL, a U.S. Department of Energy national laboratory, have developed a low-cost process for converting coal tar waste into high-quality graphene. The team stressed that the resulting can increase the performance of energy-storing supercapacitor systems by up to 55%.
Schematic illustration of the synthesis process of 3D graphene. Image from: Small Methods
According to NETL’s Christopher Matranga, one of the authors of the study, graphene has long been considered an ideal supercapacitor electrode material, but its use in commercial devices is limited because there are few methods for producing high-quality graphene at a large scale at a low cost.
Co-authors of the NETL report were Viet Hung Pham, Congjun Wang, Yuan Gao, Jennifer Weidman and Ki-Joong Kim. “Graphene is one of the most promising supercapacitor electrode materials because of its large surface area, high electrical conductivity, good chemical stability, and excellent mechanical strength,” Pham, the principal investigator on the report explained.
The NETL research discovered a process that uses coal tar pitch, an inexpensive and abundant carbon feedstock, along with a potassium carbonate (K2CO3) catalyst in a simple process to make microscopic 3D graphene with high carbon mass yields.
Coal tar pitch is a viscous liquid mixture of hydrocarbon compounds that is derived directly from coal and is frequently used as a binder or coating in the manufacture of lithium-ion battery electrodes.
The NETL report indicated that the new innovative process has produced high-quality graphene with capacitive properties that are among the highest ever reported for graphene-based supercapacitor devices.
Pham said that supercapacitors bridge a gap between conventional capacitors and traditional batteries by storing more energy than capacitors and possessing higher power densities than batteries.
According to the NETL report, the research results “overcome a long-standing challenge for fabricating practical supercapacitor electrodes, which involves balancing two conflicting characteristics: high porosity and high material density…As such, our simple synthesis method allows for the inexpensive production of electrodes and opens new opportunities for using graphene-based materials more broadly in practical supercapacitor devices.”
