Highly-Branched PtCu Nanocrystals with Low-Coordination for Enhanced Oxygen Reduction Catalysis.

Low-coordination platinum-based nanocrystals emanate great potential for catalyzing the oxygen reduction reactions (ORR) in fuel cells, but are not widely applied owing to poor structural stability. Here, several PtCu nanocrystals (PtCu NCs) with low coordination numbers were prepared via a facile one-step method, while the desirable catalyst structures were easily obtained by adjusting the reaction parameters. Wherein, the Pt1Cu1 NCs catalyst with abundant twin boundaries and high-index facets displays 15.25 times mass activity (1.647 A mgPt -1 at 0.9 VRHE) of Pt/C owing to the abundant effective active sites, low-coordination numbers and appropriate compressive strain. More importantly, the core-shell and highly developed dendritic structures in Pt1Cu1 NCs catalyst give it an extremely high stability with only 17.2% attenuation of mass activity while 61.1% for Pt/C after the durability tests (30 000 cycles). In H2-O2 fuel cells, Pt1Cu1 NCs cathode also exhibits a higher peak power density and a longer-term lifetime than Pt/C cathode. Moreover, theoretical calculations imply that the weaker adsorption of intermediate products and the lower formation energy barrier of OOH* in Pt1Cu1 NCs collaboratively boost the ORR process. This work offers a morphology tuning approach to prepare and stabilize the low-coordination platinum-based nanocrystals for efficient and stable ORR.

Microwave heating-assisted synthesis of ultrathin platinum-based trimetallic nanosheets as highly stable catalysts towards oxygen reduction reaction in acidic medium.

There are currently almost no ternary platinum-based nanosheets used for acidic oxygen reduction reactions (ORR) due to the difficulty in synthesizing ternary nanosheets with high Pt content. In this work, several ultrathin platinum-palladium-copper nanosheets (PtPdCu NSs) with a thickness of around 1.90 nm were prepared via a microwave heating-assisted method. Microwave heating allows a large number of Pt atoms to deposit into PdCu nanosheets, forming Pt-based ternary nanosheets with high Pt content. Among them, Pt38Pd50Cu12 NSs catalyst displays the highest mass activity (MA) measured in 0.1 M HClO4 of 0.932 A/mgPt+Pd which is 8.6 times of that Pt/C. Besides, Pt38Pd50Cu12 NSs catalyst also exhibits excellent stability with an extremely low MA attenuation after 80,000 cycles accelerated durability testing (ADT) tests. In the single cell tests, the Pt38Pd50Cu12 NSs catalyst manifests higher maximum power density of 796 mW cm-2 than Pt/C of 606 mW cm-2. Density functional theory (DFT) calculations indicate the weaker adsorption between Pt and O-species in Pt38Pd50Cu12 NSs leads to a significant enhancement of ORR activity. This study provides a new strategy to design and prepare ultrathin Pt-based trimetallic nanosheets as efficient and durable ORR catalysts.

NHC-mediated photocatalytic deoxygenation of alcohols for the synthesis of internal alkynes via a Csp3-Csp coupling reaction.

NHC-mediated deoxygenation of alcohols under photocatalytic conditions is described. The process provides various alkyl radicals, which can react with 1-bromoalkyne via Csp3-Csp coupling to afford internal alkynes in moderate to good yields. The method offers a new and convenient approach to synthesize internal alkynes.