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[Display omitted] Developing efficient heterogeneous catalysts for the aerobic oxidation of C–H bonds using oxygen molecule as an oxidant to produce value–added aryl ketones is a challenging task. In this study, a series of cementite–iron–carbon composites (referred to as Fe–C–T, where T represents the pyrolysis temperature) were synthesized using a metal–organic–framework–mediated sacrificial template strategy. The Fe–C–T composites consist of highly dispersed Fe/(Fe 3 C or Fe 2 O 3) nanoparticles surrounded by graphitic carbon on porous carbon supports. Under mild reaction conditions (1 atm of O 2 pressure, 353 K, 12 h), with tert–butyl hydroperoxide (0.25 equiv.) as the initiator in a green solvent water, the prepared Fe–C–973 achieved a high conversion of 98.4 % for ethylbenzene and a selectivity of 98.7 % for acetophenone. This performance was markedly superior to the comparable Fe–C–873 and Fe–C–1073, as well as the commercially available Fe–based catalysts. Kinetic studies revealed that the catalytic system followed first–order kinetics for the substrate ethylbenzene, and the activation energy over Fe–C–973 was remarkably low of 40.4 kJ/mol. The highly distributed Fe 3 C nanoparticles embedded in the porous carbon framework were identified as the most active sites for the reaction. [ABSTRACT FROM AUTHOR]

G max : The highest reaction potential energy in the reaction path. [Display omitted] • Influence of Pt on the electronic properties of α-MoC-111 surface. • Inhibition effect of Pt on carbon deposition in WGS reaction. • Preventing surface oxidation by introducing Pt in α-MoC during WGS reaction. • Role of Pt in facilitating water dissociation. Pt/α-MoC is an outstanding catalyst for the low-temperature water gas shift (WGS, CO + H 2 O → H 2 + CO 2) reaction, exhibiting elevated activity, stability, and selectivity. In this study, three significant active site models (α-MoC-111, Pt-111, and Pt 1 /α-MoC-111) in Pt/α-MoC catalyst were established to investigate the promotion effect of Pt on the WGS reaction catalyzed by Pt/α-MoC. The results indicate that a synergistic effect at the metal-carbide interface enhances chemical activity compared to pure Pt-111 and α-MoC-111. Firstly, the surface of Pt 1 /α-MoC-111 exhibits strong metal-support interaction between Pt single atom and α-MoC-111 surface. Compared to the α-MoC-111 surface, the introduction of Pt strengthens the Mo−Mo bond while weakening the Mo−C bond. Secondly, adding a Pt atom significantly increases adsorption strength for CO and H 2 O, while decreasing it for products (CO 2), oxides (O atom), and by-products (C atom). The advantage of suppressing surface carbon deposition and oxidation is observed on the surface of Pt 1 /α-MoC-111. Furthermore, elementary reactions from the three mainstream reaction pathways of the WGS reaction are systematically calculated to evaluate catalytic performance among these three active sites. On the Pt 1 /α-MoC-111 surface, activation energy barriers for H 2 O dissociation and CO oxidation are reduced. This provides theoretical ideas for designing high-efficiency α-MoC based catalysts in the future. [ABSTRACT FROM AUTHOR]

• The reaction mechanisms of each step evolve with the surface Cl/Cu ratios. • The origin of the K effect was explored by Van-der-Waals corrected DFT calculations. • Free energy analysis is consistent with the experimental observation. • KCl modifies the electronic structure of the surface. Potassium promoters are widely used in industrial catalysts of ethylene oxychlorination to achieve optimum performance. However, the origin of the promoter effect is not fully understood. Herein, we investigated the potassium promotion effect on CuCl 2 /γ-Al 2 O 3 catalyzed ethylene oxychlorination by kinetic experiments and DFT calculations. Kinetic experiments observed the effect of KCl on individual steps, and the evolution of the reaction mechanisms with Cl/Cu ratios. Further exploration via DFT found that KCl increases the formation energy of Cl vacancy (Δ E v) and thus inhibits the reduction activity, which is attributed to the shift-down of Bader charge of Cl. Δ E v boosts with the decline of Cl/Cu ratios; thus, ethylene can extract Cl atoms from the surface with a Cl/Cu ratio of 2, while it anchors to metal atoms at lower Cl/Cu ratios. The distinct adsorption modes reflect the evolution of reaction mechanisms with Cl/Cu ratios. KCl facilitates the adsorption of oxygen owing to the shift-up of the Bader charge of Cu atom. Potassium reduces the Gibbs free energy barrier of the oxidation step, which agrees with the experimental observation. It is concluded that the potassium promoter effect on the catalytic performance mainly results from the modification of the charge of surface atoms. [ABSTRACT FROM AUTHOR]