Construction Of Copper Oxide-based Heterojunction And Its Application In Electrochemical Nitrate Reduction And Detection Of Hydrogen Peroxid

With the rapid increase of population and the rapid development of industry,environmental pollution has become increasingly serious,which seriously affects human life and health.The emergence of electrocatalysis and electrochemical sensing has alleviated this problem.However,it is difficult to find catalysts with high catalytic efficiency,green environmental protection and low cost.Heterojunction nanomaterials have abundant catalytic active sites and low resistance,which are conducive to charge transfer,improve the defects of electronic structure,and endow different components with their own functions.At present,they are currently widely used in electrocatalysis,biosensing and other fields.In this thesis,low-cost copper foam was used as a substrate to construct an efficient copper oxide-based heterostructure and study its catalytic performance in electrochemical processes.The main results of the paper are as follows:1.Cu(OH)2 nanoarrays were grown in situ on copper foam substrates by chemical bath deposition method,and then calcined in different proportions of cobalt salts and urea solutions to obtain CuO NWAs@Co3O4 heterojunction materials,to investigate the performance of nitrate reduction for ammonia synthesis.Benefiting from the synergistic effect of CuO and Co3O4,after 2.5 h of electrochemical reaction in 1400 ppm NO3--N electrolyte,nitrate conversion rate,ammonia selectivity,Faraday efficiency and yield reached 96.96%,82.28%,99.17%and 1.915 mmol-1 cm-2,respectively.During the nitrate reduction process,the conversion of CuO to Cu/Cu2O can promote electron transfer,while the conversion of Co3+ to Co2+can promote the adsorption of hydrogen(H*).The synergistic effect of H*adsorption and nitrate reduction improved the performance of NRA.2.The CuO NWAs@Co3O4 heterostructure in the previous chapter was used to explore the performance of electrochemical detection of H2O2 by optimizing the reaction conditions.The results show that the sensor has a excellent electrocatalytic performance for hydrogen peroxide,the detection range is 5 × 10-7 M to 5 × 10-3 M,and the minimum detection limit is 5 × 10-7 and the sensitivity was 9868.9 μA mM-1 cm-2,with good selectivity and reproducibility.After that,it was used to detect the hydrogen peroxide produced by Hale cells and the cytotoxicity test,which proved to be promising for biochemical,physiological and pathological studies.3.Cu(OH)2 nanoarray was grown in situ on copper foam substrate,and CuO NWAs@Fe3O4 heterojunction was obtained after soaking in ferric salt and calcining.The morphology of the heterojunction was adjusted by soaking time,and the performance of CuO NWAs@Fe3O4 heterojunction for ammonia synthesis by electrocatalytic nitrate reduction was investigated.The prepared catalyst showed excellent NRA performance(nitrate conversion,ammonia selectivity and Faraday efficiency reached 96.5%,92.06%and 99.48%,respectively)and excellent stability when the catalyst was reacted at-0.27 V for 3 h.Reduction reaction in the process,the surface of the catalyst to produce large amounts of oxygen vacancy,promotes the adsorption of nitrates,CuO into Cu/Cu2O formation of active phase can promote electron transfer,and the characteristics of the Fe peak moves to the lower energy,allowing more of the electron transition to the catalyst surface and promote the freedom to form hydrogen atoms(H*)near the surface of the catalyst.The synergistic effect of atomic hydrogen(H*)adsorption and electron transfer ultimately leads to the improvement of NRA performance.