For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680 mW cm−2 at 80 °C with a low platinum loading of 0.09 mgPt cm−2, corresponding to a platinum utilization of 0.13 gPt kW−1 in the fuel cell. Good fuel cell durability is also observed. Theoretical calculations reveal that the main effective sites on such platinum single-atom electrocatalysts are single-pyridinic-nitrogen-atom-anchored single-platinum-atom centres, which are tolerant to carbon monoxide/methanol, but highly active for the oxygen reduction reaction.
It is of great importance in drug delivery to fabricate multifunctional nanocarriers with intelligent targeting properties, for cancer diagnosis and therapy. Herein, hollow-structured CuS@Cu S@Au nanoshell/satellite nanoparticles are designed and synthesized for enhanced photothermal therapy and photoswitchable targeting theranostics. The remarkably improved photothermal conversion efficiency of CuS@Cu S@Au under 808 nm near-infrared (NIR) laser irradiation can be explained by the reduced bandgap and more circuit paths for electron transitions for CuS and Cu S modified with Au nanoparticles, as calculated by the Vienna ab initio simulation package, based on density functional theory. By modification of thermal-isomerization RGD targeting molecules and thermally sensitive copolymer on the surface of nanoparticles, the transition of the shielded/unshielded mode of RGD (Arg-Gly-Asp) targeting molecules and shrinking of the thermally sensitive polymer by NIR photoactivation can realize a photoswitchable targeting effect. After loading an anticancer drug doxorubicin in the cavity of CuS@Cu S@Au, the antitumor therapy efficacy is greatly enhanced by combining chemo- and photothermal therapy. The reported nanohybrid can also act as a photoacoustic imaging agent and an NIR thermal imaging agent for real-time imaging, which provides a versatile platform for multifunctional theranostics and stimuli-responsive targeted cancer therapy.
Emerging as a new frontier in heterogeneous catalysis,
single-atom
site catalysts (SSCs) have sparked enormous attention and bring about
new opportunities to oxygen reduction electrocatalysis. Despite considerable
progress achieved recently, most of the reported SSCs suffer from
either insufficient activity or unsatisfactory stability, which severely
retards their practical application. Here, we demonstrate a novel
Ru-SSC with appropriate adsorption free energy of OH* (ΔG
OH*) to confer excellent activity and low Fenton
reactivity to maintain long-term stability. The as-developed Ru-SSC
exhibits encouraging oxygen reduction reaction turnover frequency
of 4.99 e– s–1 sites–1, far exceeding the state-of-the-art Fe-SSC counterpart (0.816 e– s–1 sites–1),
as a result of Ru energy level regulation via spontaneous OH binding.
Furthermore, Ru-SSC exhibits greatly suppressed Fenton reactivity,
with restrained generation of reactive oxygen species directly observed,
thus endowing the Ru-SSC with much more superior stability (only 17
mV negative shift after 20 000 cycles) than the Fe-SSC counterpart
(31 mV). The practical application of Ru-SSC is further validated
by its excellent activity and stability in a real fuel cell device.
Identifying effective means to improve the electrochemical performance of oxygen-evolution catalysts represents a significant challenge in several emerging renewable energy technologies. Herein, we consider metal-nitrogen-carbon sheets which are commonly used for catalyzing the oxygen-reduction reaction (ORR), as the support to load NiO nanoparticles for the oxygen-evolution reaction (OER). FeNC sheets, as the advanced supports, synergistically promote the NiO nanocatalysts to exhibit superior performance in alkaline media, which is confirmed by experimental observations and density functional theory (DFT) calculations. Our findings show the advantages in considering the support effect for designing highly active, durable, and cost-effective OER electrocatalysts.
The development of cost-effective yet highly active and robust bifunctional electrocatalyst for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) has been at the forefront of research into regenerative fuel cells and metal-air batteries. Here we report Co 9 S 8 nanoparticles grown in situ on nitrogen-and sulfur-doped porous carbon (Co 9 S 8 /NSPC) as a bifunctional catalyst for OER and ORR using poly(2-aminothiazole) as a novel all-in-one multifunctional precursor. Unexpectedly, Co 9 S 8 /NSPC exhibits a low OER overpotential, positive ORR half-wave potential, small potential gap and high durability, thus making it one of the best bifunctional OER and ORR catalysts. This may be attributed to the heteroatom doping, porous structure and synergistic effects of Co 9 S 8 and NSPC, as confirmed by density functional theory calculations. More importantly, as a proof-of-concept application, the air electrode with Co 9 S 8 /NSPC9-45 endows the Zn-air battery with a low discharge/charge overpotential and good cycling stability.
The phase stability and mechanical properties of tungsten borides W(2)B, WB, WB(2), W(2)B(5) and WB(4) were extensively studied by first-principles calculations within density functional theory. The thermodynamic and mechanical stabilities were examined. Our calculations on the enthalpy-pressure relationship and convex hulls have demonstrated that at zero pressure, the experimentally observed W(2)B-W(2)B (W(2)B-W(2)B represents W(2)B in W(2)B structure type, the same hereinafter) and WB-WB, and assumed WB(2)-ReB(2) phases are stable against decomposition into other components. The estimated hardness of WB(2)-ReB(2) is 39.4 GPa, suggesting that it is a potentially hard compound. At 60 GPa, the most stable phases are WB-WB and WB(2)-WB(2). WB-WB, WB(2)-AlB(2) and WB(4) are the ground state phases at 100 GPa. The phase transition mechanism for WB(2) was discussed. The synthesis of WB(2)-AlB(2) could be conducted at high pressures.
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