Metal-Free Hydrogen Generation from Crude Industrial Glycerol and Polymeric Silicon Waste

Abstract

The development of sustainable methods for clean hydrogen production is crucially important for the future circular economy. In this context, the prospect of deriving hydrogen directly from renewables and waste- or side-product streams is intriguing yet promising. Here, we describe a novel approach for hydrogen generation achieved by combining crude, unrefined glycerol from industrial biodiesel production as well as polymeric silicon waste. Notably, our method that relies on silane alcoholysis, works without any added transition metal catalyst and ultimately even without added co-solvent. Crucially, the practical industrial feasibility of this process was demonstrated through a solvent-free and catalyst-free scale-up (104 g), which yielded up to 5.8 L of highly pure H2 gas within 30 min. Furthermore, rigorous isotopic labeling studies combined with 1H NMR headspace gas analysis quantified the complex waste reactivity, definitively revealing that 59 ± 11% of the generated hydrogen originates directly from the glycerol backbone, while the remaining 41 ± 11% is contributed by reactive methanol and water impurities inherent to the industrial waste stream. Moreover, the silicon resin co-generated in the process was chemically recycled into useful chlorosilanes using a mild depolymerization method, strengthening the relevance of this work for a circular economy.