STEP polymer degradation: Solar thermo-coupled electrochemical depolymerization of plastics to generate useful fuel plus abundant hydrogen

A global goal is to call for common solutions to the challenge of environmental conservation. The cheap, clean and green energy and processes help to beat the hazardous pollution of plastics. An action of the STEP (Solar Thermal Electrochemical Process) on the polymer is to create a novel vision of the depolymerization of plastics to generate valuable fuels plus abundant hydrogen. In this paper, a solar thermo-coupled electrochemical system was first designed and employed to realize the plastics depolymerization to useful fuels for enhanced the solar utilization and the chemical polymer conversion. Exemplified by polypropylene (PP), the plastics were efficiently converted to light fuel and hydrogen via the solar-driven electrolysis coupled with pyrolysis. The results demonstrated that the depolymerization temperature was greatly lowered compared to conventional pyrolysis. The STEP conversion rates increased with a lift of the temperature and current. The high total conversion rate was significantly achieved by reaching 68.48% at 350 degrees C, including the solid phase of 31.52%, the liquid phase of 7.85% and the gas phase of 60.63% (w/w), which was compared to the 28.39% of the sole pyrolysis. The hydrogen was evolved during the process in the final volume of 72.5 ml, which was about 9.3 times more than that of the pyrolysis at 400 degrees C. In the outdoor experiments, the total conversion reached 66.64% at 350 degrees C, which was compared to 26.37% of the pyrolysis only. The light hydrocarbons were richly produced in the distribution of C-1-C-5 hydrocarbons while only tiny amounts of methane and ethane were probed in the pyrolysis. The common mechanism and pathways can be tentatively proposed in a mode of the radically initiated thermochemical reactions and electrochemical redox by the induction of the solar thermo-coupled electrolysis.