In situ formed Raney-Ni/Fe3O4 catalyzed reduction of NaHCO3 into acetate with Fe as reductant in water

Abstract

Abstract Conversion of CO2 into value-added chemicals is always of great interest. Previous research mainly focuses on the CO2 conversion into C1 chemicals such as formic acid. In this research, a new approach of reducing bicarbonate (CO2 source) into a C2 compound of acetate with water as the hydrogen source and Fe as re-generable reductant on a Raney-Ni (R-Ni) catalyst was proposed by mimicking the natural abiotic organic synthesis found in the deep-sea hydrothermal vent. During the reaction, the in situ formed Fe3O4 together with the R-Ni generated a R-Ni/Fe3O4 bifunctional catalyst, in which the in situ formed Fe3O4 probably promote a high adsorption enthalpy of C1 intermediates on the Ni catalyst, leading to an optimum acetate yield of 4.1%. Mechanistic study revealed that the catalytic mechanism of the R-Ni/Fe3O4 was probably attributed to i) enhancement of in situ hydrogen activation and formate synthesis over the Fe3O4 site; ii) CO formation and activation over the Raney-Ni site; iii) formation and adsorption of methylene from CO on the R-Ni surface; and iv) acetate formation from the combination of formate and methylene over R-Ni site. This research developed a new way to reduce CO2 into C2 products with water as the hydrogen source, which provides new insights into the CO2 conversion to products with C ≥ 2.