Study On The Photocatalytic Performance Of Lead-free Double Perovskite Cs₂AgInCl₆

In recent years,the increasing pollution of organic dyes has severely damaged the ecosystem.Therefore,organic pollutant removal technology,especially photocatalytic technology,has attracted widespread attention.Common photocatalysts,such as metal sulfides,metal oxides,metal nitrides,etc.,have the disadvantages of high recombination rate of photogenerated electron-hole pairs and low light utilization efficiency.For this reason,looking for highly efficient new catalysts has become one of the research hotspots.Recently,the emerging lead halide perovskite,due to its excellent photoelectric properties,began to be applied to the field of photocatalysis,and showed excellent photocatalytic performance,which has attracted people’s attention.However,this type of material has the problems of lead toxicity and poor stability.The results show that lead-free double perovskite is environmentally friendly,stable and non-toxic,so it is an ideal alternative material for lead based perovskite,and it is expected to develop a new type of photocatalyst with high efficiency and stability.In addition,the double perovskite is easy to adjust its band gap by doping and realize the broadening of its spectral response range,which is beneficial to the development of photocatalysts with broad spectral response.In this paper,the lead-free double perovskite Cs₂AgInCl₆ with direct band gap and long carrier lifetime was selected as the catalyst to degrade the water-insoluble organic pollutant Sudan Red Ⅲ,and its photocatalytic performance and mechanism were studied.Moreover,the band gap is adjusted by Bi3+doping Cs₂AgInCl₆ to obtain a wide spectral response catalyst in the ultraviolet-visible（UV-Vis）range.The details are as follows:Firstly,Cs₂AgInCl₆ double perovskite was prepared in acidic solution by precipitation method.The sample was octahedral particles with face-centered cubic phase,about 5～10 μm in size.EDS surface scanning proved that the surface distribution of various elements in the sample was relatively uniform,and the ratio was close to 2:1:1:6,indicating that Cs₂AgInCl₆ was successfully prepared.Sultan Red Ⅲ can be rapidly degraded to colorless by 20 mg Cs2AgInC16 within 16 min under the irradiation of 300 W mercury lamp.The degradation rate is about 98.5%,and it is almost completely degraded,showing high photocatalytic efficiency.Further high-resolution mass spectrometry（HRMS）and liquid chromatography（HPLC）have also obtained similar results.In addition,Cs₂AgInCl₆ shows good cycle stability and long-term stability,and can also rapidly degrade MO,MR and RhB.Free radical trapping experiments and electron paramagnetic resonance spectroscopy（EPR）confirmed that ·O2-may play a major role in the photocatalytic degradation of Cs₂AgInCl₆.The results show that Cs₂AgInCl₆ can be used as an efficient and stable photocatalyst.Secondly,the band gap of Cs2AgInC16 is about 3.33 eV,corresponding to the ultraviolet light region.In order to broaden its spectral response range,Bi3+doping is used to adjust its band gap.The XRD results showed that with the increase of Bi3+doping,no impurity peak appeared,and the peak position shifted to a small angle,which proved that Bi3+was successfully doped into the crystal lattice.The UV-Vis absorption spectrum shows that the absorption edge red-shifts with the increase in the amount of doping,and the corresponding band gap can be shifted to about 2.68 eV.At the same time,it showed a good light stability under the irradiation of the xenon lamp for 20 h.Under a 300 W xenon lamp,Cs2AgIn0.6Bi0.4Cl6（band gap 2.73 eV）can almost completely degrade Sudan Red Ⅲ within 4 min,with a degradation rate of 98.6%,showing a faster catalytic efficiency.In addition,the results of comparative experiments show that broadening the spectral absorption range can increase the photocatalytic degradation rate of the sample.At the same time,Cs2AgIn0.6Bi0.4Cl6 also showed good cycle stability and long-term stability.Free radical capture experiments and EPR confirmed that ·O2-plays a major role in the photocatalytic degradation of Cs2AgIn0.6Bi0.4Cl6.The results show that the band gap of Cs₂AgInCl₆ can be adjusted to the visible region by doping,and it may be used as a catalyst for broad spectrum absorption.