Biomass Waste Carbonization in Piranha Solution: A Route to Hypergolic Carbons?

In the present work we report for first time carbonization of biomass waste, such as stale bread and spent coffee, in piranha solution (H2SO4-H2O2) at ambient conditions. Carbonization is fast exothermic, resulting formation carbon nanosheets decent yields 25–35%, depending on starting material. The structure morphology were verified by X-ray diffraction, Raman, photoelectron microscopy techniques. Interestingly, obtained spontaneously ignites upon contact with fuming nitric acid HNO3 conditions, thus offering a rare example hypergolicity involving solid fuel (i.e., hypergolic carbon). Based relatively large interlayer spacing as-produced carbons, simple structural model proposed observed hypergolicity, wherein molecules fit gallery space carbon, exposing its basal plane defect sites to spontaneous reaction strong oxidizing agent. This finding may pave way towards new type propellants based latter exclusively waste solution.