Simultaneous silicon production and purification via in-flight hydrogen plasma

Silicon is a critical mineral, central to photovoltaics, semiconductors, and emerging battery anodes, yet its production still relies on carbon-intensive reduction of high-grade SiO 2 followed by energy-intensive purification. Replacing carbon with molecular hydrogen is impractical because SiO 2 is highly stable and reduction favours volatile SiO (g) , rather than elemental silicon. Here we show that in-flight hydrogen plasma creates a different pathway for silicon formation from silica-source powders. Quartz and processed rice hulls were treated rapidly for 2 min in a continuous 10% H 2 –Ar in-flight plasma reactor. Crystalline silicon formed across reactor deposits, including Si-rich particles locally exceeding 2N purity. Phase-resolved XRD, SEM–EDS, and EBSD analyses show silicon together with SiC, partially reduced SiO x , residual amorphous silica, and impurity-rich oxide phases. These results demonstrate an in-flight plasma route for converting both primary quartz and Si-rich rice-processing waste into upgraded silicon-bearing products, linking low-carbon silicon production with waste-derived silica valorisation.