Rational design and controllable synthesis of catalysts with unique structure and composition are effective ways to promote electrocatalytic ethanol oxidation, thus contributing the direct ethanol fuel cells to gain ground. Herein, 2.5 nm-thin PtIrCu ternary alloy ultrathin nanowires (UNWs) with high-density planar defects are synthesized via oriented attachment with the assistance of H 2 . By adjusting the contents of Ir and Cu atoms, we find that the structure of the products changed from nanowires (NWs) to nanoparticles with the increase of Ir content. Density functional theory calculations show that when Cu atoms are replaced by Ir atoms, the vacancy formation energy of Pt atoms is increased, making the Pt atoms difficult to be activated by H 2 , which is not conducive to the formation of a one-dimensional structure. The optimal Pt 43 Ir 32 Cu 25 UNWs achieve excellent ethanol electrooxidation reaction activity (1.05 A•mg −1 Pt and 1.67 mA•cm −2 ), for it can significantly reduce the onset potential and improve the ability of CO anti-poisoning. The significant improvement in catalytic performance is attributed to the synergistic effect of the alloy and the NW structure with high-density planar defects.
The design of the nanostructure of palladium-based nanocatalysts is considered to be a very effective way to improve the performance of nanocatalysts. Recent studies have shown that multiphase nanostructures can increase the active sites of palladium catalysts, thus effectively improving the catalytic efficiency of palladium atoms. However, it is difficult to regulate the phase structure of Pd nanocatalysts to form a compound phase structure. In this work, PdSnP nanocatalysts with different compositions were synthesized by fine-regulating the doping amount of phosphorus atoms. The results show that the doping of phosphorus atoms not only changes the composition of PdSn nanocatalysts but also changes the microstructure, forming amorphous and crystalline multiphase structures. This multiphase nanostructure contains abundant interfacial defects, which effectively promotes the electrocatalytic oxidation efficiency of Pd atoms in small-molecule alcohols. Compared with the undoped PdSn nanocatalyst (480 mA mg Pd −1 and 2.28 mA cm −2 ) and the commercial Pd/C catalyst (397 mA mg Pd −1 and 1.15 mA cm −2 ), the mass (1746 mA mg Pd −1) and specific activities (8.56 mA cm −2 ) of PdSn 0.38 P 0.05 nanocatalysts in the methanol oxidation reaction were increased by 3.6 and 3.8 times and 4.4 and 7.4 times, respectively. This study provides a new synthesis strategy for the design and synthesis of efficient palladium-based nanocatalysts for the oxidation of small-molecule alcohols.
The catalytic performance of a catalyst is mainly determined by its surface structure, and superior catalytic activities have been observed on low-coordination surface sites. However, poor stability of low-coordination sites was observed during catalysis due to easier oxidation of these sites. By far, fabricating the catalysts with abundant low-coordination sites and stabilizing them still faces a significant challenge. Herein, we show the synthesis of an emerging type of PdPt alloy nanoframe wherein the ridges are composed of rugged surfaces with high-density, low-coordination sites. The synthesis of nanoframes mainly consists of two steps: preparation of PdPt alloy concave nanocubes and subsequent site-selective chemical etching. The nanoframe structure would endow low-coordination sites with excellent catalytic stability, preventing dissolution, migration, and aggregation of these active sites during catalysis. Electrochemical studies on the oxygen reduction reaction (ORR) catalysis show that it can deliver superior mass activities tens of times higher than that of commercial Pt/C catalysts in a broad pH range (from 1 to 13), with negligible activity decay after 40 000 cycles. In addition, as-prepared nanoframes can also exhibit excellent catalytic activity and stability toward methanol and ethanol oxidation reactions, with mass activities up to 19.55 and 28.96 A/mg Pd+Pt , respectively, which are 19 and 47 times that of commercial Pt/C catalysts. Theoretical calculations reveal that the coexistence of PdPt alloy components and high-density, low-coordination sites both is important for enhanced catalytic activities. This new strategy to stabilize the low-coordination sites on Pt-based electrocatalysts by constructing frame structures would shed new light on the rational design and synthesis of highly efficient electrocatalysts.
Taste is one of the basic senses of living organisms and can recognize sour, bitter, salty, sweet and umami tastes. Bitter taste receptor is a class of G protein-coupled receptors capable of sensing bitterness. Initially, bitter taste receptor was thought to be only found in the taste buds of the tongue, palate and throat. Recent research has shown that in addition to the oral cavity, the bitter taste receptor is also present in the intestinal tract, respiratory tract, urinary tract, vascular smooth muscle, nervous system, thyroid gland and other tissues and organs to regulate body homeostasis and resist disorders . In this review, we focus on the effects of the bitter taste receptor outside the oral cavity to lay the groundwork for future research.
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