Electrodissolution‐Coupled Hafnium Alkoxide Synthesis with High Environmental and Economic Benefits. Issue 11 (4th May 2022)

• Record Type: Journal Article
• Authors: Li, Shuai; Yang, Shenghai; Li, Kangkang; Lai, Yanqing; Deng, Chaoyong; Wang, Changhong
• Is Part Of: ChemSusChem. Volume 15:Issue 11(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-05-04
• Subjects: electrochemistry -- hafnium -- hafnium alkoxide synthesis -- negative-carbon hydrogen -- waste-free; Green chemistry -- Periodicals; Sustainable engineering -- Periodicals; Chemistry -- Periodicals; Chemical engineering -- Periodicals; 660
• DOI: 10.1002/cssc.202200474
• Languages: English
• ISSNs: 1864-5631

Abstract

Abstract: 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. Abstract : A green system for hafnium alkoxide synthesis was proposed. Simultaneous heterogeneous Hf dissolution and ethanol dehydrogenation followed by spontaneous solution‐based binding of alkoxy with Hf 4+ ions gave Hf(OEt)4 . After the optimum conditions – electrolyte, temperature, current densities, etc. – had been determined, a proof‐of‐concept experiment achieved waste‐free production of Hf(OEt)4 with high purity and yield. Besides the system's green credentials, it showed a high net profit of 30 477 USD per kg Hf(OEt)4 and could be extended to the synthesis of other hafnium alkoxides.