Nanodiamond Synthesis from Coal via Flash Joule Heating.

Abstract

As the coal industry transitions toward cleaner production, it demands advanced coal utilization strategies. Converting low-value coal into high-value nanodiamonds (NDs) is a promising approach. NDs exhibit exceptional properties with broad potential applications. NDs are typically synthesized from high-purity graphite, whereas coal serves as a lower-cost alternative. However, existing coal-based NDs (C-NDs) are synthesized in low purity and low efficiency, restricting their applicability and scalability. To address these challenges, a fluorine (F)-assisted flash Joule heating (FJH) method is developed using coke as a feedstock to synthesize C-NDs within 1 s. After post-treatment, C-NDs achieve ∼ 100% purity with an 8% yield and exhibit thermal stability comparable to commercial NDs. Theoretical calculations indicate that F atoms induce electronic rearrangement and promote the formation of interlayer C-C bonds. The application of C-NDs as seed crystals was demonstrated to produce a high-quality diamond film. Life cycle assessment (LCA) shows that C-NDs perform better than the high-pressure high-temperature (HPHT) method in cost, carbon emissions, water consumption, and electricity usage. Given their economic and environmental benefits, a coal-to-diamond production system is proposed that may contribute to cleaner coal utilization and the advancement of the coal industry.