Reaction Mechanism and Selectivity Tuning of Propene Oxidation at the Electrochemical Interface

Abstract

Electrochemical conversion of propene is a promising technique for manufacturing commodity chemicals by using renewable electricity. To achieve this goal, we still need to develop high-performance electrocatalysts for propene electrooxidation, which highly relies on understanding the reaction mechanism at the molecular level. Although the propene oxidation mechanism has been well investigated at the solid/gas interface under thermocatalytic conditions, it still remains elusive at the solid/liquid interface under an electrochemical environment. Here, we report the mechanistic studies of propene electrooxidation on PdO/C and Pd/C catalysts, considering that the Pd-based catalyst is one of the most promising electrocatalytic systems. By electrochemical in situ attenuated total reflection Fourier transform infrared spectroscopy, a distinct reaction pathway was observed compared with conventional thermocatalysis, emphasizing that propene can be dehydrogenated at a potential higher than 0.80 V, and strongly adsorb via μ-CCHCH3 and μ3-η2-CCHCH3 configuration on PdO and Pd, respectively. The μ-CCHCH3 is via bridge bonds on adjacent Pd and O atoms on PdO, and it can be further oxidized by directly taking surface oxygen from PdO, verified by the H2 18O isotope-edited experiment. A high surface oxygen content on PdO/C results in a 3 times higher turnover frequency than that on Pd/C for converting propene into propene glycol. This finding highlights the different reaction pathways under an electrochemical environment, which sheds light on designing next-generation electrocatalysts for propene electrooxidation.

Ag-doped Pd nano-dendritic for promoting the electrocatalytic oxidation of ethylene to ethylene glycol

“…6a). 28,29 The Ag-OH band length is 2.179 and 2.131 Å when doped at the surface and subsurface, which is longer than Pd-OH, 2.097 and 2.034 Å, respectively. The lower binding energy of the Ag-doped model enables the subsequent coupling steps to become easier.…”

“…Generally, the selective electrooxidation of ethylene to EG would require the successive transfer of two OH groups via the *C 2 H 4 intermediate. 28,29 Evidently, the regulation of OH binding energy on the electrocatalyst surface becomes essential. We suppose that doping metals into Pd-based electrocatalysts might modulate the OH binding energy and thus improve the EG selectivity.…”

Dynamically Reversible Interconversion of Molecular Catalysts for Efficient Electrooxidation of Propylene into Propylene Glycol

“…9,10 Unfortunately, this economic and environmentally friendly process suffers from a low yield rate and selectivity up to date. 11,12 As such, it is highly desirable but challenging to achieve the effective electrooxidation of propylene into PG.…”

“…The one-step electrooxidation of propylene into PG could eliminate cost-adding steps for the production and hydrolysis of propylene oxide . In addition, this process utilizes sustainable water as the oxygen source under ambient conditions, avoiding the consumption of polluted or costly oxidants. , Unfortunately, this economic and environmentally friendly process suffers from a low yield rate and selectivity up to date. , As such, it is highly desirable but challenging to achieve the effective electrooxidation of propylene into PG.…”

Propane Oxidative Dehydrogenation on Nanosized Boron Carbide: Effect of Boron Content and Its Oxidation Implicated by DFT Calculations

“…Light olefins, such as propene, are essential chemical building blocks in the chemical industry for a vast array of polymers and fine chemicals. − The global production of propene exceeds 100 Mt/year since 2017, and the industrial demand for propene continues growing, which is forecasted to reach 130 million tons in 2023. − Conventional production methods for propene, such as steam cracking or fluid catalytic cracking, are tremendously energy demanding and increase environmental concerns . The dehydrogenation of propane, either via direct propane dehydrogenation (PDH) and oxidative propane dehydrogenation (ODHP), offers an alternative method with high atom economy in propene production .…”