Inorganic Chemistry

Electrolytic Synthesis of White Phosphorus is Promoted in Oxide-Deficient Molten Salts

Authors

Abstract

Elemental white phosphorus (P4) is a key feedstock for the entire phosphorus-derived chemicals industry, spanning everything from herbi-cides to food additives. The electrochemical reduction of phosphate salts could enable the sustainable production of P4; however, such electrosynthesis requires the cleavage of strong, inert P—O bonds. By analogy to the promotion of bond activation in aqueous electrolytes with high proton activity (Brønsted-Lowry acidity), we show that low oxide anion activity (Lux-Flood acidity) enhances P—O bond activa-tion in molten salt electrolytes. We develop electroanalytical tools to quantify the oxide dependence of phosphate reduction, and find that Lux acidic phosphoryl anhydride linkages enable selective, high-efficiency electrosynthesis of P4 at a yield of 95% faradaic efficiency. These fundamental studies provide a foundation that may enable the development of low-carbon alternatives to legacy carbothermal synthesis of P4.

Version notes

Article has been revised to increase focus on the fundamental science advancements and new field opportunities that these studies provide, rather than its initial focus on the process as a single industrial product / the associated commercial metrics.

Content

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Supplementary material

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Supplementary Materials for Efficient Electrosynthesis of White Phosphorus from Molten Condensed Phosphate Salts
This PDF file includes: Materials and Methods Supplementary Text Supplementary References Figs. S1 to S18 Tables S1 to S8