Catalytic conversion of carbon dioxide (CO2) into value-added chemicals is of pivotal importance, well the cost of capturing CO2 from dilute atmosphere is super challenge. One promising strategy is combining the adsorption and transformation at one step, such as applying alkali solution that could selectively reduce carbonate (CO32-) as consequences of CO2 adsorption. Due to complexity of this system, the mechanistic details on controlling the hydrogenation have not been investigated in depth. Herein, Ru/TiO2 catalyst was applied as a probe to elucidate the mechanism of CO32- activation, in which with thermodynamic and kinetic investigations, a compact Langmuir-Hinshelwood reaction model was established which suggests that the overall rate of CO32- hydrogenation was controlled by a specific C-O bond rupture elementary step within HCOO- and the Ru surface was mainly covered by CO32- or HCOO- at independent conditions. This assumption was further supported by negligible kinetic isotope effects (kH/kD ≈ 1), similarity on reaction barriers of CO32- and HCOO- hydrogenation (ΔH‡hydr,Na2CO3 and ΔH‡hydr,HCOONa) and a non-variation of entropy (ΔS‡hydr ≈ 0). More interestingly, the alkalinity of the solution is certainly like a two sides in a sword and could facilitate the adsorption of CO2 while hold back catalysis during CO32- hydrogenation.

Recently major advances were gained on the designed proteins aimed to generate biomolecular mimics of proteases. Although such enzyme-like catalysts must still suffer refinements for improving the catalytic activity, at the moment, they represent a good example of artificial enzymes to be tested in different fields. Herein, a de novo designed homo-heptameric peptide assembly (CC-Hept) where the esterase activity towards p-nitro-phenylacetate was obtained for introduction of the catalytic triad (Cys-His-Glu) into the hydrophobic matrix, is the object of the present combined molecular dynamics and quantum mechanics/molecular mechanics investigation. Constant pH Molecular Dynamics simulations on the apoform of CC-Hept suggested that the Cys residues are present in the protonated form. Molecular dynamics (MD) simulations of the enzyme-substrate complex evidenced the attitude of the enzyme-like system to retain water molecules, necessary in the hydrolytic reaction, in correspondence of the active site, represented by the Cys-His-Glu triad on each of the seven chains, without significant structural perturbations. A detailed reaction mechanism of esterase activity of CC-Hept-Cys-His-Glu was investigated on the basis of the quantum mechanics/molecular mechanics calculations employing a large quantum mechanical (QM) region of the active site. The proposed mechanism is consistent with available esterases kinetics and structural data. The roles of the active site residues were also evaluated. The deacylation phase emerged as the rate-determining step, in agreement with esterase activity of other natural proteases.

The effects of alloying Pt with transition metal Ni on oxygen reduction reaction (ORR) mechanisms was investigated based on a systematic density functional theory (DFT) calculation explored in the present work. New insights into the ORR mechanisms were reported at the atomic level on Pt-segregated Pt3Ni(111). Only one molecular chemisorption state with the end-on OOH configuration was identified through geometry optimization and minimum energy path (MEP) analysis; top-bridge-top configuration as observed on pure Pt(111) was not identified on Pt-segregated Pt3Ni(111), indicating that alloying Pt with Ni influences the intermediates of ORR, and leads to only the dissociation mechanism of chemisorption state OOH species being involved in acid medium on Pt-segregated Pt3Ni(111). By contrast, the dissociation mechanisms of chemisorbed O2 molecule with top-bridge-top configuration and OOH species both were involved on pure Pt(111). The rds of the entire four-electron ORR was changed after Pt alloying with Ni. The rds of the entire ORR is the proton and electron transfer to O2 to form OOH on Pt-segregated Pt3Ni(111), whereas it is the reaction of O atom protonation to form OH species on pure Pt(111), indicating that sublayer Ni strongly influences the rds of ORR. The comparison of the ORR mechanisms explained that Pt3Ni alloy enhanced the ORR electrocatalytic activity more than pure Pt. The effect of electrode potential on ORR pathway on the pure Pt and Pt3Ni alloy was considered to obtain further insights into the electrochemical reduction of O2. Results showed that the proton and electron transfer becomes difficult at high potential. The ORR can easily proceed when the electrode potential lowers. For pure Pt- and Pt-based alloys, this phenomenon may imply the origin of the overpotential.