High rate and cycling stable Li metal anodes enabled with aluminum-zinc oxides modified copper foam

Metallic Li is a promising anode material for high energy density batteries but it suffers from poor stability and formation of unsafe dendrites. Previous studies demonstrated that 3 D metal foams are able to improve the stability of Li metal but the properties of these foams are inherently limited. Here we report a facile surface modification approach via magnetron sputtering of mixed oxides that effectively modulate the properties of Cu foams for supporting Li metal with remarkable stability. We discovered that hybrid Li anodes with Li metal thermally infused to aluminum-zinc oxides(AZO) coated Cu foams have significantly improved stability and reactivity compared with pristine Li foils and Li infused to unmodified Cu foams. Full cells assembled with a Li Fe PO4 cathode and a hybrid anode maintained low and stable charge-transfer resistance(<50) during 500 cycles in carbonate electrolytes, and exhibited superior rate capability(~100 m Ah g-1 at 20 C) along with better electrochemical reversibility and surface stability. The AZO modified Cu foams had superior mechanical strength and afforded the hybrid anodes with minimized volume change without the formation of dendrites during battery cycling. The rational construction of surface architecture to precisely control Li plating and stripping may have great implications for the practical applications of Li metal batteries.

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia

Ambient electrochemical nitrogen fixation is a promising and environmentally benign route for producing sustainable ammonia,but has been limited by the poor performance of existing catalysts that promote the balanced chemisorption of N2 and subsequent electrochemical activation and hydrogenation.Herein,we describe the highly selective and efficient electrohydrogenation of nitrogen to ammonia using a hollow nanorod-based hierarchically graphitic carbon electrocatalyst with abundant atomically dispersed Mn sites.We discovered that the electron interactions strengthen the interfacial binding between nitrogen and active Mn Lewis acidic hotspots.The Lewis acid-base interactions promote the chemisorption and lock up nitrogen on the active sites and suppress proton adsorption.The proton-coupled electron transfer cleavage of the nitrogen triple bond through an associative mechanism was confirmed under lower overpotential,which delivered high ammonia yield of 67.5μg h−1 mgcat.−1 and Faradaic efficiency of 13.7% at−0.25 V versus the reversible hydrogen electrode,along with∼100% selectivity and significantly enhanced electrochemical stability(about 88.8% current retention over 50 h potentiostatic test)under mild conditions.Our strategy is versatile to tailor the nitrogen fixation performance of single-atom catalysts with atomic accuracy.

Diameter dependent doping in horizontally aligned high-density N-doped SWNT arrays

We reported the growth of horizontally aligned nitrogen-doped single-walled carbon nanotubes (SWNTs) on quartz substrates. The synthesized SWNTs were comprehensively characterized at the single nanotube level. Owing to the highly aligned nature of the nanotubes, we were able to investigate the diameter dependent doping mechanism through systematic resonant Raman spectroscopy studies. Other than the formerly found narrowing effect by N-doping, we proposed that the nanotube diameter affects the introduction of N atoms into the carbon lattice in an elaborate way. The obtained doping level increased along with the nanotube diameter but lost the increasing trend when the diameter became larger and experienced a slight decrease after reaching the local peak value. These insights about the heteroatom doping into the carbon nanotubes could benefit the development of the carbon nanotube based functional materials and extend their application in a broad range of areas.