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Advanced functional materials: high entropy alloys with multiple active sites were first used in nitrogen reduction at full pH

wallpapers News 2020-12-07

electrocatalytic nitrogen reduction (NRR) is a kind of nitrogen fixation technology which uses nitrogen water as raw materials to produce NH3 under relatively mild conditions. Because of its environmentally friendly properties it has become a new research hotspot in the field of electrocatalysis. The central link of electrocatalytic process is the preparation of efficient catalyst. In the past few years a variety of effective electrocatalysts have emerged. Transition metals play an important role in the NRR process can be used to alleviate the dynamics of n ≡ n bond excitation. However low NH3 yield high overpotential poor stability are still the biggest challenges of NRR. With the continuous progress of material science new materials are emerging. By precisely controlling the coordination entropy high entropy alloys can be synthesized from five or more metal elements with the same atomic ratio. Because of its unique corrosion resistance adjustable performance in harsh conditions it has been widely concerned by scientists. The traditional synthesis method of high entropy alloy often needs extremely harsh conditions the product morphology is not uniform the yield is relatively low so it is necessary to find a more suitable method to prepare high entropy alloy with nano size uniform morphology.

Professor Wang Lei Professor Lai Jianping of Qingdao University of science technology have prepared rufeconicu high entropy alloy nanoparticles with a size distribution of about ~ 16 nm at low temperature (≤ 250 ℃) atmospheric pressure were applied to electrocatalytic NRR for the first time. Due to the large number of metal sites in high entropy alloys the catalytic activity of NRR can be improved by the synergistic effect of various metals in the process of nitrogen reduction. The research team synthesized rufeconicu high entropy alloy nanoparticles in oil phase at low temperature (≤ 250 ℃) atmospheric pressure. These nanoparticles have uniform morphology with a size of ~ 16 nm have good dispersion with carbon loading to avoid the agglomeration of nanoparticles in the catalytic process. Subsequently this material was applied to NRR. The experimental data showed that in 0.1 M KOH electrolyte the NH3 yield of 57.1 μ g h – 1 mg cat − 1 (11.4 μ g h – 1 cm – 2) was obtained at a low overpotential of 0.05 V vs. rhe in 0.1 M KOH electrolyte the Faraday efficiency was 38.5% which was the highest ammonia production of the materials reported at this overpotential. At the same time after 100 h stability test it still maintained good catalytic activity structural stability. The test results in other pH electrolyte show that the high entropy alloy is suitable for NRR at all pH. The team also carried out theoretical calculation on the synthesized materials concluded that the t-fe site is the adsorption site of N2 while Ru Ni co Cu have good surface hydrogenation ability which can inhibit the hydrogen adsorption to produce H2 during the catalytic process promote the hydrogenation process of N2.

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