The newly-assisted catalytic mechanism of surface hydroxyl species performed as the promoter in syngas-to-C2 species on the Cu-based bimetallic catalysts

In the conversion process of syngas-to-C_(2)species,the OH species are inevitably produced accompanying the production of key intermediates CH_(x)(x=1-3),traditionally,the function of surface OH species is generally accepted as the hydrogenating reactive species.This work for the first time proposed and confirmed the assisted catalytic mechanism of surface OH species that performed as the promoter for syngas-to-C_(2)species on Cu-based catalysts.DFT and microkinetic modeling results reveal that the produced OH species accompanying the intermediates CH_(x)production on the MCu(M=Co,Fe,Rh)catalysts can stably exist to form OH/MCu catalysts,on which the presence of surface OH species as the promoter not only presented better activity and selectivity toward CH_(x)(x=1-3)compared to MCu catalysts,but also significantly suppressed CH_(3)OH production,providing enough CH_(x)sources to favor the production of C_(2)hydrocarbons and oxygenates.Correspondingly,the electronic properties analysis revealed the essential relationship between the electronic feature of OH/MCu catalysts and catalytic performance,attributing to the unique electronic micro-environment of the catalysts under the interaction of surface OH species.This new mechanism is called as OH-assisted catalytic mechanism,which may be applied in the reaction systems related to the generation of OH species.

Thermodynamics of NaHCO_3 decomposition during Na_2CO_3-based CO_2 capture

Amine-basedcarbon-capture technologies have been shown to be energetically expensive and to cause significant environmental and epidemiological impacts due to their volatility.Bicarbonate formation from carbon dioxide's reaction with water has been suggested as an effective alternative for capturing CO_2;however,the thermodynamics of this reaction are not well understood.This study experimentally determined the equilibrium constant of sodium bicarbonate(Na HCO_3)decomposition to sodium,water,and carbon dioxide;the study also compared the equilibrium constant to theoretical calculations.Using a combination of experimentation and thermodynamic relationships,the unitless equilibrium constants of the forward and reverse reactions were calculated accurately(error<±9%and<±4%,respectively).Equilibrium data were calculated using enthalpy and entropy values of each component of Na HCO_3decomposition at temperatures ranging from 25 to 155°C respectively.These results offer more data essential to optimizing Na HCO_3use in environmentally friendly nextgeneration CO_2-capture technologies.