Cu,N-codoped Hierarchical Porous Carbons as Electrocatalysts for Oxygen Reduction Reaction

It remains a huge challenge to develop nonprecious electrocatalysts with high activity to substitute commercial Pt catalysts for oxygen reduction reactions (ORR). Here, the Cu,N-codoped hierarchical porous carbon (Cu–N–C) with a high content of pyridinic N was synthesized by carbonizing Cu-containing ZIF-8. Results indicate that Cu–N–C shows excellent ORR electrocatalyst properties. First of all, it nearly follows the four-electron route, and its electron transfer number reaches 3.92 at −0.4 V. Second, both the onset potential and limited current density of Cu–N–C are almost equal to those of a commercial Pt/C catalyst. Third, it exhibits a better half-wave potential (∼16 mV) than a commercial Pt/C catalyst. More importantly, the Cu–N–C displays better stability and methanol tolerance than the Pt/C catalyst. All of these good properties are attributed to hierarchical structure, high pyridinic N content, and the synergism of Cu and N dopants. The metal–N codoping strategy can significantly enhance the activity of electrocatalysts, and it will provide reference for the design of novel N-doped porous carbon ORR catalysts

Origin of Enhanced Activities for CO Oxidation and O₂ Reaction over Composition-Optimized Pd₅₀Cu₅₀ Nanoalloy Catalysts

It has been shown experimentally that Pd₅₀Cu₅₀ nanoalloy achieves the maximum activity for CO oxidation (COox) and oxygen reduction reaction (ORR) on composition-tuned PdCu bimetallic catalysts, but the origin of this catalytic synergy remains unclear. In this work, results of our density functional theory (DFT) calculations show that the weakest adsorption strength of O₂ in terms of the most pronounced charge transfer between Pd and Cu is responsible for the experimentally observed highest catalytic activity of Pd₅₀Cu₅₀ catalyst for both COox and ORR over a series of composition-tuned PdCu nanoalloys. For COox, the lowest barrier energy is attributed to the weakest adsorption strength of O₂ on Pd₅₀Cu₅₀ catalyst. In ORR, the lowest barrier energy for O₂ dissociation and also the weakest adsorption strength of O, OH, and OOH species are related to the weakest adsorption strength of O₂ over the catalyst with a 50:50 ratio of Pd/Cu. Our work represents the first attempt to address an in-depth correlation between the theoretical and experimental data on the highly active PdCu catalysts, the results of which has significant implications for the design of advanced nanoalloy catalysts with superior catalytic synergy in terms of the alloy compositions

Discovery of AZD3199, An Inhaled Ultralong Acting β₂ Receptor Agonist with Rapid Onset of Action

A series of dibasic des-hydroxy β₂ receptor agonists has been prepared and evaluated for potential as inhaled ultralong acting bronchodilators. Determination of activities at the human β-adrenoreceptors demonstrated a series of highly potent and selective β₂ receptor agonists that were progressed to further study in a guinea pig histamine-induced bronchoconstriction model. Following further assessment by onset studies in guinea pig tracheal rings and human bronchial rings contracted with methacholine (guinea pigs) or carbachol (humans), duration of action studies in guinea pigs after intratracheal (i.t.) administration and further selectivity and safety profiling AZD3199 was shown to have an excellent over all profile and was progressed into clinical evaluation as a new ultralong acting inhaled β₂ receptor agonist with rapid onset of action