High Selective Electrochemical Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol on RuO₂–SnO₂–TiO₂/Ti Electrode

Abstract

Electrocatalytic hydrogenation is a promising method to synthesize high value-added chemicals under mild conditions. However, in the case of converting cinnamaldehyde (CAL) into cinnamyl alcohol (COL), this approach is accompanied by the competitive side reactions, including hydrodimerization, CC saturation, and hydrogen evolution. In this work, a high selectivity to cinnamyl alcohol of 88.86% at 58.00% conversion was successfully achieved on a thermally decomposed RuO2–SnO2–TiO2/Ti cathode with a rutile sosoloid crystal structure, which surpasses the low selectivity (<15%) over various metal electrodes. Density functional theory calculation findings demonstrate that CAL interacts with the active RuO2 sites preferentially via CO rather than CC, with the energy barrier of CAL hydrogenation toward COL being significantly reduced. The introduction of SnO2 is efficient to improve the Faradaic efficiency by restraining hydrogen evolution, but would result in dimers as the main products at high content. In addition, low pH value and high electrode overpotential benefit the generation of COL and the inhibition of dimerization products.

Black SnO2–TiO2 Nanocomposites with High Dispersion for Photocatalytic and Photovoltalic Applications

“…15 Typically, the combination of SnO 2 and TiO 2 can be classified into two categories: (a) SnO 2 and TiO 2 particles separate from each other to form a layer−layer [16][17][18]20,21 or core−shell structure; 22−27 (b) SnO 2 and TiO 2 particles mix with each other to be a rather homogeneous structure. 19,28,29 For the second style, due to the high hydrolysis rate of titanium alkoxides, most of the SnO 2 −TiO 2 syntheses start from sol solutions followed by gelation, 19 solvothermal reaction, thermal decomposition, 28 or precipitation. 30 In the gelation and particle formation processes, SnO 2 and TiO 2 can undergo separation processes because of different hydrolysis and condensation rates of titanium and tin precursors.…”

Electrocatalysis with Molecular Transition-Metal Complexes for Reductive Organic Synthesis

“…Another important challenge is here to reduce the carbonyl to the alcohol in a chemoselective way, avoiding the ketyl radical coupling and the hydrogenation of other unsaturations (e.g., C=C) when present ( Figure 5 b). 48 , 49 To drive carbonyl hydrogenation to the desired selectivity, molecular electrocatalysts have been investigated, 50 , 51 mostly based on Ni, 52 , 53 Fe, 52 , 53 Ru, 54 and Rh 55 − 57 metal complexes, with a body of work using homogeneous and immobilized Rh bipyridine type complexes. 55 − 57 …”

Acrylonitrile Conversion on Metal Cathodes: How Surface Adsorption Determines the Reduction Pathways

“…Electrochemical reduction is an economical and environmentally friendly method for producing high-value chemicals via the hydrogenation of unsaturated bonds such as CC, CO, and NO. − With electron transfer driven by current from sustainable energies, the electrochemical method utilizes water or protons as the hydrogen source, and thus, it has potential to substitute for the thermocatalytic ones employing toxic and expensive redox agents . The reduction of unsaturated compounds on a cathode is generally accompanied by three categories of reactions: (i) the direct electrochemical hydrogenation (ECH) of the unsaturated bond, (ii) the electrohydrodimerization (EHD) of unsaturated bonds to form dimers, and (iii) the hydrogen evolution reaction (HER). − It has been widely recognized that the preference of these three paths is related to the HER activity of the cathode. When varying the electrode material from HER-active to inert, the rate of the HER decreases while that of EHD increases, and ECH mainly occurs on a medium HER-active electrode …”