The synergy of SPR effect and Z-scheme of Ag on enhanced photocatalytic performance of 3DOM Ag/CeO2-ZrO2 composite

Abstract

Using polystyrene spheres (PS) as a template, a kind of three-dimensionally ordered macroporous (3DOM) Ag/CeO2-ZrO2 material was synthesized by the sol–gel combined with the decompression filling method. A series of characterization methods, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV–vis/DRS), Scanning electron microscopy (SEM), High-resolution transmission electron microscopy (HR-TEM), and N2 adsorption–desorption measurements were used to study its composition, structure, morphology, and surface physicochemical properties. The synthesized composite material 3DOM Ag/CeO2-ZrO2 shows a good crystal structure, open and transparent arrangement in a three-dimensional space. Meanwhile, compared with the sample without PS treatment, the composite material has a smaller band gap energy value, which means under the excitation of light, it is easier to produce electron–hole pairs and enables to absorb more reactive molecules on the surface of the catalyst, thus improving the photocatalytic performance of the composite. And after loading Ag metal on the composite, the light absorption of the catalyst is extended to the visible region by the surface plasmon resonance effect (SPR), resulting in promoting the absorption efficiency of light. During multimode photocatalytic degradation experiments of Congo Red (CR), 3DOM Ag/CeO2-ZrO2 composite exhibited an excellent photocatalytic performance. Under ultraviolet light, its catalytic performance was much better than that of both commercial catalyst P25 and the sample without loading Ag. At the same time, in the photocatalytic hydrogen evolution experiment, 3DOM Ag/CeO2-ZrO2 showed a stronger ability of water splitting into hydrogen, whose hydrogen yield (53 μmol in 8 h) was about 4 times than that of P25, indicating 3DOM Ag/CeO2-ZrO2 had the ability of photodegradation and photolysis of water. In addition, superoxide free radical (O2−), hydroxyl radical (OH), and hole (h+) were considered as main reactive groups in the photocatalytic process according to capture experimental results. Moreover, the transfer effect of Ag as Z-Scheme in the photocatalytic reaction was speculated as well.