Platinum-group-metal quaternary alloys with lattice defects for enhanced oxygen electrocatalysis.

We propose a facile coreduction method to synthesize a platinum-group-metal quaternary alloy anchored on nitrogen-doped hollow carbon spheres (PtPdRuIr/HCS) by using [MClx]y--1-butyl-3-methylimidazole (M = Pt, Pd, Ru, and Ir) ionic liquid. Owing to the steric hindrance of the imidazolium cations, Pt-group metal atoms of different sizes can be deposited at approximately the same pace for the growth of an alloy with lattice defects. The lattice-distorted PtPdRuIr/HCS exhibits enhanced activity toward oxygen electroreduction when benchmarked against Pt counterparts.

In Situ Growth of Sub-50-nm Zirconium Aminobenzenedicarboxylate Metal-Organic Framework Nanocrystals for Carbon Dioxide Capture.

Controlled synthesis of sub-50-nm metal-organic frameworks (MOFs), which are usually called porous coordination polymers, exhibits huge potential applications in gas storage and separation. Herein, surface-confined growth of zirconium aminobenzenedicarboxylate MOF (UIO-66-NH2) nanocrystals on polypyrrole hollow spheres (PPyHSs) is achieved through covalently grafted benzene dicarboxylic acid ligands using bridged molecules. PPyHSs modified with ligand molecules prohibit excessive growth of UIO-66-NH2 nanocrystals on their confined surface, resulting in smaller-sized nanocrystals (<50 nm) and a monolayer UIO-66-NH2 coating. Benefiting from the homogeneous dispersion of UIO-66-NH2 nanocrystals with a smaller size (40 ± 10 nm), the as-prepared PPyHSs@UIO-66-NH2 hybrids with high specific surface area and pore volume exhibit remarkable CO2 capture performance. Moreover, the time required to reach the maximum CO2 adsorption capacity shortens with decreasing UIO-66-NH2 crystals size. As a proof of concept, the proposed covalent grafting strategy can be used for synthesizing sub-50-nm UIO-66-NH2 nanocrystals for CO2 capture.

Palladium Enhanced Iron Active Site - An Efficient Dual-Atom Catalyst for Oxygen Electroreduction.

Metal-nitrogen-carbon (M-C/N) electrocatalysts have been shown to have satisfactory catalytic activity and long-term durability for the oxygen reduction reaction (ORR). Here, a strategy to prepare a new electrocatalyst (Fe&Pd-C/N) using a unique metal-containing ionic liquid (IL) is exploited, in which Fe & Pd ions are positively charged species atomically dispersed by coordination to the N of the N-doped C substrate, C/N. X-ray absorption fine structure, XPS and aberration-corrected transmission electron microscopy results verified a well-defined dual-atom configuration comprising Fe+2.x -N4 coupled Pd2+ -N4 sites and well-defined spatial distribution. Electronic control of a coupled Fe-Pd structure produces an electrocatalyst that exhibits superior performance with enhanced activity and durability for the ORR compared to that of commercial Pt/C (20%, Johnson Matthey) in both alkaline and acid media. Density functional theory calculations indicate that Pd atom can enhance the catalytic activity of the Fe active sites adjacent to Pd sites by changing the electronic orbital structure and Bader charge of the Fe centers. The excellent catalytic performance of the Fe&Pd-C/N electrocatalyst is demonstrated in zinc-air batteries and hydrogen-air fuel cells.