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Advanced materials: synthesis of nitrate by room temperature electrocatalytic nitrogen oxidation based on Ru doped TiO2 / RuO2

wallpapers News 2020-08-26
As one of the most stable nitrogen-containing compounds in aerobic environment

nitrate is very important in industrial / agricultural production other fields. At present ammonia oxidation method is mainly used to synthesize nitrate in industry. At the same time large-scale ammonia synthesis often relies on energy intensive Haber Bosch process technology. Because this technology needs to be carried out under high temperature high pressure it has high energy consumption huge carbon dioxide emissions. Room temperature electrochemical nitrogen fixation has the advantages of simple operation low energy consumption environmental friendliness. It is considered as a new technology that is most likely to replace the traditional industrial nitrogen fixation methods. Therefore it has attracted extensive attention of scholars at home abroad in recent years. Generally speaking

in the process of electrocatalytic nitrogen oxidation (nor) the conversion of nitrogen to nitrate mainly goes through two steps: the first step is the electrochemical conversion of inert nitrogen to active no * intermediate which is also the rate limiting step of nor; the second step is the non electrochemical step (that is no * o * generated by the decomposition of electrocatalytic water generate nitrate through redox reaction). It can be seen that in the whole nor process it is necessary not only to inhibit the first competitive four electron water desorption oxygen reaction (OER) but also to carry out appropriate oer reaction to provide o * reactants for the second step. Therefore the reasonable design of efficient nor electrocatalyst is a challenging problem.

recently Professor Yan Qingyu Professor Zhou Kun of Nanyang Polytechnic University of Singapore have proposed a simple convenient new method of electrocatalytic nitrogen oxidation (nor) to produce nitrate which can effectively combine the nor process oer kinetics correspondingly use different content of Ru doped TiO2 (ruxtiyo2) as the concept verification catalyst. Density functional theory (DFT) calculations show that Ru δ is the main active center of nor process. Doping Ru into the lattice of commercial TiO2 particles can cause the center of d-b of Ru site to move up thus enhancing the activation ability of inert nitrogen molecules. DFT calculation shows that the adsorption energy of ru4 (pure phase RuO2) for nitrogen molecule is △ GN2 = - 0.02 EV; compared with ru4 the binding energy of Ru δ (0 < δ < 4) to nitrogen molecule is obviously enhanced its adsorption energy is △ GN2 = -0.61 ev. Therefore the change of Ru oxidation state (ru4 → ruδ ) can effectively accelerate the electrochemical kinetics of the first step of nor. In addition the moderate doping of Ru ions will lead to the formation of a small amount of RuO2 on the surface of TiO2 particles which provides the corresponding oer active sites to promote the subsequent oxidation of no * intermediate to nitrate. However when there is excessive RuO2 in the catalyst the oer process will be dominant which is unfavorable to the selectivity of nor the Faraday efficiency of nitrate synthesis. The optimal Ru doping amount is 2.97 wt.% (2.79 Ru / TiO2). In 0.1 M Na2SO4 neutral solution the yield of nitrate can reach 161.9 mmol H-1 gcat-1 the optimal Faraday efficiency is 26.1%.

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