Confined Mn^(2+)enables effective aerobic oxidation catalysis

Effective and mild activation of O_(2) is essential but challenging for aerobic oxidation. In heterogeneous catalysis, high-valence manganese oxide(e.g., +4) is known to be active for the oxidation, whereas divalent MnO is ineffective due to its limited capacity to supply surface oxygen and its thermodynamically unstable structure when binding O_(2) in reaction conditions. Inspired by natural enzymes that rely on divalent Mn^(2+), we discovered that confining Mn^(2+) onto the Mn_(2)O_(3) surface through a dedicated calcination process creates highly active catalysts for the aerobic oxidation of 5-hydroxymethylfurfural, benzyl alcohol, and CO.The Mn_(2)O_(3)-confined Mn^(2+) is undercoordinated and efficiently mediates O_(2) activation, resulting in 2–3 orders of magnitude higher activity than Mn_(2)O_(3) alone. Through low-temperature infrared spectroscopy, we distinguished low-content Mn^(2+) sites at Mn_(2)O_(3) surface, which are difficult to be differentiated by X-ray photoelectron spectroscopy. The combination of in-situ energydispersive X-ray absorption spectroscopy and X-ray diffraction further provides insights into the formation of the newly identified active Mn^(2+) sites. By optimizing the calcination step, we were able to increase the catalytic activity threefold further.The finding offers promising frontiers for exploring active oxidation catalysts by utilizing the confinement of Mn^(2+)and oftenignored calcination skills.

Pt@h-BN core-shell fuel electrocatalysis confined cell electrocatalysts wit under outer shells

Two-dimensional （2D） materials such as graphene and hexagonal boron nitride （h-BN） can be used as robust and flexible encapsulation overlayers, which effectively protect metal cores but allow reactions to occur between inner cores and outer shells. Here, we demonstrate this concept by showing that Pt@h-BN core-shell nanocatalysts present enhanced performances in H2/O2 fuel cells. Electrochemical （EC） tests combined with operando EC-Raman characterizations were performed to monitor the reaction process and its intermediates, which confirm that Pt-catalyzed electrocatalytic processes happen under few-layer h-BN covers. The confinement effect of the h-BN shells prevents Pt nanoparticles from aggregating and helps to alleviate the CO poisoning problem. Accordingly, embedding nanocatalysts within ultrathin 2D material shells can be regarded as an effective route to design high-performance electrocatalysts.

A superior catalyst for ozone decomposition: NiFe layered double hydroxide

Ground-level ozone is harmful to human beings and ecosystems,while room-temperature catalytic decomposition is the most effective technology for ozone abatement.However,solving the deactivation of existing metal oxide catalysts was caused by oxygen-containing intermediates is challenging.Here,we successfully prepared a two-dimensional NiFe layered double hydroxide (NiFe-LDH) catalyst via a facile co-precipitation method,which exhibited stable and highly efficient performance of ozone decomposition under harsh operating conditions (high space velocity and humidity).The NiFe-LDH catalyst with Ni/Fe=3and crystallization time over 5 hr (named Ni3Fe-5) exhibited the best catalytic performance,which was well beyond that of most existing manganese-based oxide catalysts.Specifically,under relative humidity of 65%and space velocity of 840 L/(g·hr),Ni3Fe-5 showed ozone conversion of 89%and 76%for 40 ppmV of O3within 6 and 168 hr at room-temperature,respectively.We demonstrated that the layered structure of NiFe-LDH played a decisive role in its outstanding catalytic performance in terms of both activity and water resistance.The LDH catalysts fundamentally avoids the deactivation caused by the occupancy of oxygen vacancies by oxygen-containing species (H2O,O-,and O2-) in manganese-based oxide.This study indicated the promising application potential of LDHs than manganese-based oxide catalysts in removal of gaseous ozone.