No abstract

Propane dehydrogenation (PDH) has great potential to meet the increasing global demand for propylene, but the widely used Pt‐based catalysts usually suffer from short‐term stability and unsatisfactory propylene selectivity. Herein, we develop a ligand‐protected direct hydrogen reduction method for encapsulating subnanometer bimetallic Pt–Zn clusters inside silicalite‐1 (S‐1) zeolite. The introduction of Zn species significantly improved the stability of the Pt clusters and gave a superhigh propylene selectivity of 99.3 % with a weight hourly space velocity (WHSV) of 3.6–54 h−1 and specific activity of propylene formation of 65.5 molnormalC3normalH6  gPt−1 h−1 (WHSV=108 h−1) at 550 °C. Moreover, no obvious deactivation was observed over PtZn4@S‐1‐H catalyst even after 13000 min on stream (WHSV=3.6 h−1), affording an extremely low deactivation constant of 0.001 h−1, which is 200 times lower than that of the PtZn4/Al2O3 counterpart under the same conditions. We also show that the introduction of Cs+ ions into the zeolite can improve the regeneration stability of catalysts, and the catalytic activity kept unchanged after four continuous cycles.

Electrified solid/liquid interfaces are the key to many physicochemical processes in a myriad of areas including electrochemistry and colloid science. With tremendous efforts devoted to this topic, it is unexpected that molecular-level understanding of electric double layers is still lacking. Particularly, it is perplexing why compact Helmholtz layers often show bell-shaped differential capacitances on metal electrodes, as this would suggest a negative capacitance in some layer of interface water. Here, we report state-of-the-art ab initio molecular dynamics simulations of electrified Pt(111)/water interfaces, aiming at unraveling the structure and capacitive behavior of interface water. Our calculation reproduces the bell-shaped differential Helmholtz capacitance and shows that the interface water follows the Frumkin adsorption isotherm when varying the electrode potential, leading to a peculiar negative capacitive response. Our work provides valuable insight into the structure and capacitance of interface water, which can help understand important processes in electrocatalysis and energy storage in supercapacitors.

Developing active and durable electro-catalysts toward ethanol oxidation reaction (EOR) with high selectivity toward the C-C bond cleavage is an important issue for the commercialization of direct ethanol fuel cell. Unfortunately, current ethanol oxidation electro-catalysts (e.g., Pt, Pd) still suffer from poor selectivity for direct oxidation of ethanol to CO, and rapid activity degradation. Here we report a facile route to the synthesis of a new kind of cyclic penta-twinned (CPT) Rh nanostructures that are self-supported nanobranches (NBs) built with 1-dimension CPT nanorods as subunits. Structurally, the as-prepared Rh NBs possess high percentage of open {100} facets with significant CPT-induced lattice strains. With these unique structural characteristics, the as-prepared CPT Rh NBs exhibit outstanding electrocatalytic performance toward EOR in alkaline solution. Most strikingly, the selectivity of complete conversion ethanol to CO on the CPT Rh NBs is measured to be as high as 14.5 ± 1.1% at -0.15 V, far exceeding that for single-crystal tetrahedral nanocrystals, icosahedral nanocrystals, and commercial Rh black, as well as majority of reported values for Pt or Pd-based electro-catalysts. By combining with density functional theory calculation, the effects of different structural features of Rh on EOR are definitively elucidated. It was found that the large amount of open Rh (100) facets dominantly contribute to the outstanding activity and exceptionally high selectivity, while the additional tensile strain on (100) planes can further boost the catalytic activity by enhancing the adsorption strength and lowering the reaction barrier of dehydrogenation process of ethanol. As a proof of concept, the present work shows that rationally optimizing surface and electronic structure of electro-catalysts by simultaneously engineering their surface and bulk structures is a promising strategy to promote the performance of electro-catalysts.