Strain-Enhanced Phase Transformation of Iron Oxide for Higher Alcohol Production from CO₂

Abstract

Conversion of CO2 to higher alcohols (HAs) and higher hydrocarbons (HCs) has a greater advantage compared to C1 products because of their high energy density and wide range of applications in daily life. Despite the immense potential of these chemicals, not much of scientific research has been focused on the conversion of CO2 to HAs. In the present work, we have introduced the concept of strain in designing the material to enhance the CO2 to HA performance. We introduced strain in a traditional iron-based catalyst, Fe2O3, by the introduction of indium (In), which facilitates the selective conversion of CO2 to HA. An optimum strain favored a 36.7% CO2 conversion with a 42% HA selectivity, and a record yield of 15.42%. The strain has been tuned further with the introduction of K as a promoter. The introduced strain upon In substitution and K promotion favored the conversion of CO2, which is mapped by powder X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. Further, the change in the mechanism upon In incorporation and K promotion has been probed by in situ diffuse reflectance infrared fourier transform spectroscopy, and it is found that the OCH x intermediate, which produces HAs, is more prominent upon In substitution, which favored the enhancement of HA production compared to that of pristine Fe2O3.

Development of Multifunctional Tandem Catalysts for CO2 Hydrogenation to Higher Alcohols

“…The catalyst achieved high STY of 169.6 mg gcat -1 h -1 with an 87.4% proportion of C2+OH among all alcohols at 4 MPa and 320°C. Peter et al [65] introduced In into a conventional iron-based catalyst along with K as promoter, positing that In modification altered the reaction pathway of traditional Fe3O4 catalyst (Fig. 2).…”

Development of Multifunctional Catalysts for the Direct Hydrogenation of Carbon Dioxide to Higher Alcohols

“…The results show that the presence of reduced In x O y with oxygen vacancies is essential for CO 2 hydrogenation to higher alcohols. Peter et al [ 111 ] introduced In into a conventional iron-based catalyst along with K as a promoter, positing that In modification alters the reaction pathway of the traditional Fe 3 O 4 catalyst ( Figure 2 ). Initially, CO 2 is converted into CO in the Fe 3 O 4 phase via the RWGS reaction, followed by hydrocarbon formation on the Fe x C y phase.…”

“… Brief schematic of the mechanism of formation of higher alcohols and other hydrocarbons based on the intermediates observed during an in situ DRIFTS measurement. Reprinted with permission from Peter et al [ 111 ]. Copyright (2022) ACS.…”

Toward Unifying the Mechanistic Concepts in Electrochemical CO2 Reduction from an Integrated Material Design and Catalytic Perspective

“…Electrocatalytic CO 2 RR can occur through a 2-, 4-, 6-, 8-, 12-, or even an 18-electron reduction pathway to convert CO 2 into various gaseous (carbon monoxide, methane, ethane, and ethylene) and liquid products (formic acid, methanol, ethanol, acetic acid, propanol, etc.). [3,4] However, a lack of thorough mechanistic understanding impedes the utilization of the true potential of this technology which still faces significant challenges in areas like a) low reaction rates or current densities (typically ≤ 200 mA cm −2 : one order less than requirements of commercial electrolyzers) & CO 2 mass transport limitations b) slow electron-transfer (ET) kinetics, c) unsatisfactory product selectivity for some of the desired reduction products (methanol, ethanol, and higher hydrocarbons) [5][6][7] & durability (typically ≤ 100 h). [8] Most of the electrocatalysts reported so far can produce below 200 mA cm −2 , which is far less than industrial electrolyzers, usually operating at more than 70% efficiency at current densities above 200 mA cm −2 .…”