Siyu Yao

Electrochemical reduction of CO2 to synthesis gas with controlled CO/H2 ratios

The electrochemical carbon dioxide reduction reaction (CO2RR) to simultaneously produce carbon monoxide (CO) and hydrogen (H2) has been achieved on carbon supported palladium (Pd/C) nanoparticles in an aqueous electrolyte. The synthesis gas product has a CO to H2 ratio between 0.5 and 1, which is in the desirable range for thermochemical synthesis of methanol and Fischer–Tropsch reactions using existing industrial processes. In situ X-ray absorption spectroscopy in both near-edge (XANES) and extended regions (EXAFS) and in situ X-ray diffraction show that Pd has transformed into β-phase palladium hydride (β-PdH) during the CO2RR. Density functional theory (DFT) calculations demonstrate that the binding energies of both adsorbed CO and H are significantly weakened on PdH than on Pd surfaces, and that these energies are potential descriptors to facilitate the search for more efficient electrocatalysts for syngas production through the CO2RR.

Combining CO 2 reduction with propane oxidative dehydrogenation over bimetallic catalysts

The inherent variability and insufficiencies in the co-production of propylene from steam crackers has raised concerns regarding the global propylene production gap and has directed industry to develop more on-purpose propylene technologies. The oxidative dehydrogenation of propane by CO2 (CO2-ODHP) can potentially fill this gap while consuming a greenhouse gas. Non-precious FeNi and precious NiPt catalysts supported on CeO2 have been identified as promising catalysts for CO2-ODHP and dry reforming, respectively, in flow reactor studies conducted at 823 K. In-situ X-ray absorption spectroscopy measurements revealed the oxidation states of metals under reaction conditions and density functional theory calculations were utilized to identify the most favorable reaction pathways over the two types of catalysts.The oxidative dehydrogenation of propane by CO2 (CO2-ODHP) can potentially fill the gap of propylene production while consuming a greenhouse gas. Here, the authors identify non-precious FeNi and precious NiPt catalysts supported on CeO2 as promising catalysts for CO2-ODHP and dry reforming, respectively, in flow reactor studies.

Active sites for tandem reactions of CO2 reduction and ethane dehydrogenation

Significance Catalytic activity or selectivity of a supported metal catalyst is predominantly determined by its active site structure. Rational optimization of supported metal catalysts requires fundamental insights into active sites and structure–function relationships. Here, we convincingly identify two types of metal–oxide active sites and successfully correlate them with the corresponding catalytic performance for CO2-assisted dehydrogenation of ethane. Controlled synthesis of the two distinct active sites enables rational manipulation of the activity and selectivity, offering an opportunity to efficiently convert the underutilized ethane from shale gas to value-added products while mitigating anthropogenic CO2 emissions. Ethylene (C2H4) is one of the most important raw materials for chemical industry. The tandem reactions of CO2-assisted dehydrogenation of ethane (C2H6) to ethylene creates an opportunity to effectively use the underutilized ethane from shale gas while mitigating anthropogenic CO2 emissions. Here we identify the most likely active sites over CeO2-supported NiFe catalysts by using combined in situ characterization with density-functional theory (DFT) calculations. The experimental and theoretical results reveal that the Ni–FeOx interfacial sites can selectively break the C–H bonds and preserve the C–C bond of C2H6 to produce ethylene, while the Ni–CeOx interfacial sites efficiently cleave all of the C–H and C–C bonds to produce synthesis gas. Controlled synthesis of the two distinct active sites enables rational enhancement of the ethylene selectivity for the CO2-assisted dehydrogenation of ethane.