The conventional thermal method of preparing hafnium alkoxides [Hf(OR)4 , R=alkyl] - excellent precursors for gate-dielectric HfO2 on semiconductors - is severely hindered by its unsatisfactory environmental and economic burdens. Herein, we propose a promising electrodissolution-coupled Hf(OR)4 synthesis (EHS) system for green and efficient electrosynthesis of Hf(OR)4 . The operational principle of the electrically driven system consists of two simultaneous heterogeneous reactions of Hf dissolution and alcohol dehydrogenation, plus a spontaneous solution-based combination reaction. In applying ethanol as solvent and Hf metal as electrodissolution medium, we achieved waste-free production of high-purity hafnium ethoxide [Hf(OEt)4 ] with an equivalent "a concomitant" reduction in CO2 emission of 187.33 g CO2 per kg Hf(OEt)4 and a high net profit of 30 477 USD per kg Hf(OEt)4 . This system is very competitive with the thermal process, which unavoidably releases substantial waste and CO2 for a net profit of 27 700 USD per kg Hf(OEt)4 . We anticipate that the environmental and economic benefits of the EHS process could pave the way for its practical application.
Keywords: electrochemistry; hafnium; hafnium alkoxide synthesis; negative-carbon hydrogen; waste-free.
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