Catalytic reduction and reductive functionalisation of carbon dioxide with waste silicon from solar panel as the reducing agent

Abstract

Waste silicon wafer recovered from the solar panel production process acted as a reducing agent for reduction and reductive functionalization of CO2 with fluoride catalyst.

Fluoride Catalysts and Organic Additives for Conversion of CO2 to Formic Acid and Methanol using Powdered Silicon as Reducing Agent

“…The proposed reaction pathway of the conversion of CO 2 to formic acid or methanol is shown in Scheme 2. According to previous reports, fluoride catalyst cleaves Si−Si bond of metallic silicon to form Si−H species, which effectively reduce CO 2 to formic acid [8,11b] . The formation of Si−H and Si−F species have been confirmed in a similar homogeneous reaction system using a disilane [6,11b] .…”

“…[6,11b] The SiÀ F species and hydroxide ion reacts to give silanol and regenerated fluoride ion. [8] This regeneration process is also confirmed by homogeneous reaction suing disilane. [11b] Further, the obtained formic acid is activated using an arylboronic acid and nucleophilic attack of Si-hydride reduces the formic acid to methanol.…”

“…Other divalent cations such as MgF 2 were inactive during the reaction. [8] In the case of KF, the addition of 18-crown-6 facilitated the formation of formic acid. These results indicate that the size of cations and solubility of fluoride salts affects its reactivity.…”

“…Fluoride salts containing inorganic monovalent cations, such as K and Cs, catalyzed the reduction reaction, while sodium fluoride did not. Other divalent cations such as MgF 2 were inactive during the reaction [8] . In the case of KF, the addition of 18‐crown‐6 facilitated the formation of formic acid.…”

“…In these methods, the silicon surface is pretreated with a large amount of hydrofluoric acid. Alternatively, our group reported the use of a commercially available powdered silicon for reducing CO 2 in the presence of tetrabutylammonium fluoride [6‐8] …”