Understanding the roles of metals and atomic structures in activating various elementary steps of electrocatalytic reactions can help rational design of binary or ternary catalysts for promoting activity toward desirable products via favorable pathways. Here we report on a newly developed ternary Au@PtIr core−shell catalyst for ethanol oxidation reaction (EOR) in alkaline solutions, which exhibits an activity enhancement of 6 orders of magnitude compared to AuPtIr alloy catalysts. Analysis of in situ infrared reflection absorption spectra for Au@PtIr and its bimetallic subsets, Au@Pt and PtIr alloy, found that monatomic steps and Au-induced tensile strain on PtIr facilitate C−C bond splitting via ethanol dissociative adsorption and Ir promotes dehydrogenation at low potentials. As evidenced by the CO band being observed only for the PtIr alloy that is rather inactive for ethanol dissociative adsorption, we propose that splitting the C−C bond at the earliest stage of EOR activates a direct 12-electron full oxidation pathway because hydrogen-rich fragments can be fully oxidized without CO as a poisoning intermediate. The resulting synergy of complementary effects of Au core and surface Ir leads to an outstanding performance of Au@PtIr for EOR as characterized by a low onset potential of 0.3 V and 8.3 A mg −1 all-metals peak current with 57% currents generated via full ethanol oxidation.

PtM (M = transition metals) nanomaterials have been recognized as promising catalysts for the oxygen reduction reaction (ORR) in fuel cells, with a much higher performance than pure Pt. However, the insufficient durability issue of PtM is often raised because of the fast dissolution of M in acid, impeding their commercialization. Herein, we report on a Ketjenblack (KB)-supported, nitrogen (N)-doped intermetallic PtNiN (Int-PtNiN/KB) catalyst that exhibits remarkably enhanced ORR activity and stability in an acidic electrolyte, superior to those of disordered PtNi/KB, disordered PtNiN/KB, and commercial Pt/C. The experimental results show that Int-PtNiN/KB has a distinctive ordering structure of alternating Ni4–N and Pt planes; we attribute the origin of the superior stability of this catalyst to the combined effect of the Ni4–N formation and the unique intermetallic structure, which effectively precludes Ni dissolution from the core. The density functional theory calculations suggest that the tensile strain introduced by the formation of an intermetallic phase and N-doping optimizes the binding of oxygenated species on the Pt surface and enable highly efficient electron transfer, leading to the enhanced ORR performance. This study offers an appropriate route for further enhancing both the activity and durability of PtM catalysts through a facile synthesis method by annealing in an NH3 gas under appropriate conditions.

Classification consistency and accuracy are viewed as important indicators for evaluating the reliability and validity of classification results in cognitive diagnostic assessment (CDA

Strong bonding interactions between a transition metal and a substrate or support is one of the most effective strategies to immobilize subnanometer scale clusters or atoms in heterogeneous catalysis. We show that such a type of phenomenon can take place on a Mo2N surface. Combined experimental and theoretical studies show that strong metal–support interactions between face-centered cubic-structured γ-Mo2N and cobalt have been confirmed to effectively anchor subnanometer Co clusters and prevent their aggregation. The results of X-ray absorption near edge structure, ambient pressure X-ray photoelectron spectroscopy, and density functional theory revealed electronic perturbations in the nitride-bonded cobalt not seen on a strongly active oxide such as CeO2. A charge transfer from Co to Mo2N was observed with a significant stabilization of the Co 3d levels, which prevents the full decomposition of CO2. The subnanometer Co loaded on γ-Mo2N catalysts exhibited very high selectivity to the product CO, whereas the undesirable methanation activity, typically inevitable on traditional Co/oxide catalysts, was successfully suppressed. As a consequence of the electronic perturbations induced by the nitride, the cobalt was not able to fully dissociate the CO2 molecule to generate C or CH x fragments necessary for methane production. Under reaction conditions, the strong bonding between Co and γ-Mo2N maintained the subnanometer geometry of Co, leading to a remarkable selectivity and stability.