【文章內(nèi)容簡介】 (6)??23 42l8OHCuAl????? (7)??2442O?????When the cathodic bias is applied, Cu2+ is reduced to Cu+ by gaining one electron (reaction (1)) or to Cu by gaining two electrons (reaction (2)). In addition, hydrogen ions are reduced to hydrogen gas (reaction (3)). In the subsequent anodic reactions, part of the reduced Cu+ are reoxidized into Cu2+ (reaction (5)), which, together with hydroxyl ions and dissolved Al3+, participate in the formation of copper aluminates by plex coprecipitation of Al3+ and Cu2+ hydroxides and deposition triggered by exterior potential (simplified by reaction (6) and (7)). During the whole process, pores are continuously nucleated at the centre by the anodic reaction based on the fieldenhanced oxide dissolution mechanism (Parkhutik and Shershulsky 1992。 Li et al. 2022。 Choi et al. 2022), releasing Al3+ ions (reaction (4)) that contribute to the evolution of CuAl2O4 spinel. Unlike other report (Choi 2022), both Cu2+ and Cu+ did not undergo the process of Cu2O and CuO formation in this case, since the formation of CuAl2O4 from solidstate reaction 6 / 40of CuO and Al2O3 only take place at high calcination temperature ( 2022). More over, no intermediate CuO and Cu2O phase were detected from the XRD pattern of as synthesized CuAl2O4Cu nanorods. It must, however, be underlined that the mechanism of CuAl2O4 evolution in the electrochemical environment is under further investigation, given the bination of two plicated chemical and electrochemical processes: coprecipitation of aluminumCu (Ⅱ) hydroxides at certain pH value and potential induced deposition. PhotocatalysisAfter establishing the synthesis and characterization of the new CuAl2O4Cu nanorods, we further studied their function in visiblelight photocatalyis. To this end, methyl orange (MO) is selected as a model dyeing pollutant because it is one of the most important mercial dyes, has a very short excitedstate lifetime, and is stable to visible and near UV light (Yu et al. 2022). The degradations of methyl orange under different conditions were presented to evaluate the visiblelight photocatalysis of assynthesized CuAl2O4 Cu nanorods. As show in Figure 4, the methyl orange did not change without photocatalyst under visible illumination (350 W xenon lamp, λ 400 nm), suggested it was stable under the visible light irradiation. In the system of CuAl2O4 Cu catalyst, the degradation rate reached to 80% within 3 hours under the same illumination. This suggested that the degradation of methyl orange was mainly due to the photocatalysis of CuAl2O4 Cu hybrids.The visiblelight photocatalysis of CuAl2O4 Cu hybrid nanorods can be explained by the low bandgap of CuAl2O4 and metal enhanced charge separation at the metal/semiconductor interface. As show in figure 4b, the prepared CuAl2O4 Cu hybrids possess an excellent lightabsorption characteristic over the UVvisible region, with an upper limit wavelength around 750 nm. The solar spectrum matching optical properties is significant in the photocatalytic solar energy conversion(Mingce et al. 2022). The apparent bandgap of this hybrid system is calculated as eV, lower than the previously reported eV for CuAl2O4 nanopowders (Yanyan 2022). Besides, the utility of metalsemiconductor hybrid structures for photocatalysis relies on charge separation at the metal/semiconductor interface(Cozzoli et al. 2022。 Chandrasekharan et al. 2022。 Wood et al. 2022。 Bao et al. 2022), which can effectively restrain rapid electronhole rebination in the semiconductor. Therefore the significant photocatalysis activity of CuAl2O4Cu hybrid may be assigned to the charge separation that take place at the CuAl2O4 /Cu interface followed by degradation of MO. a) The degradation rate of methyl orange in CuAl2O4Cu system prepared under 13V versus 7 / 40irradiation time. b) UVVis reflectance spectrum of the sample prepared under 13V, 200Hz.3 Conclusions and perspectivesThe method presented here illustrates a new synthesis route for the growth of aligned CuAl2O4 Cu nanorods in ordered alumina pores by electrochemical reaction in a simple solution of CuAl2O4 and MgSO4. The growth process can be viewed as simultaneously occurred reduction of Cu (Ⅱ) cation and nucleation of CuAl2O4 nanocrystallite. The nanosized Cu particles and CuAl2O4 crystallite stacked together along the direction of the nanorods and can grow into pure microsize octahedral CuAl2O4 crystallite. It is worth noting that the formation of CuAl2O4 nanocrystal was triggered by ac potential in a direct way at room temperature, which gave rise to the possibility of synthesizing CuAl2O4 spinel under a relative mild condition. Photocatalysis experiment of the as synthesized CuAl2O4 Cu hybrid shows considerable degradation rate of methyl orange under visiblelight irradiation, which renders potential application of CuAl2O4 Cu nanorods as a visiblelight photocatalyst for the degradation of recalcitrant anic pollutants.ReferencesAmmundsen, B., and Paulsen, J. Novel lithiumion cathode materials based on layered manganese oxides [J]. Advanced Materials, 2022, 13(1213): 943956.Luders, U., Barthelemy, A., Bibes, M., Bouzehouane, K., Fusil, S., Jacquet, E., Contour, ., Bobo, ., Fontcuberta, J., and Fert, A. NiFe2O4: A versatile spinel material brings new opportunities for spintronics [J]. Advanced Materials, 2022, 18(13): 17331736.Zhang, ., Rondinone, ., Ma, ., Shen, J., and Dai, S. 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