摘要
为了将可再生太阳能转化为化学物质,探索具有宽光谱响应的光催化剂用于光催化分解水越来越受到人们的关注.作为铋基层状金属氧化物的一员,铬酸铋(Bi2CrO6)的带隙约为1.9 eV,在利用大范围太阳光谱方面具有潜力.然而,Bi2CrO6较差的电荷分离性能限制了其在光催化中的应用.本文采用微波辅助水热合成方法制备了具有规则形貌的Bi2CrO6晶体,该晶体具有结晶度高、形貌均匀的优点.与传统制备方法相比,微波辐照实现了体系的快速加热,极大地加速了成核和生长的化学反应,从而在几分钟内形成了Bi2CrO6晶体.微波辅助合成的Bi2CrO6晶体在光催化和光电化学测试中表现出更好的光生电荷分离以及水氧化活性.此外实验中观察到光生电子和空穴在Bi2CrO6晶体的不同晶面之间发生空间分离,通过进一步在不同晶面上光沉积选择性负载还原和氧化助催化剂,显著增强了光催化活性.这项工作为制备高效太阳能转换的半导体光催化剂提供了一种可行的解决方案.
Abstract
The conversion of renewable solar energy into chemical energy is an important topic in research.Recently,bismuth chromate(Bi2CrO6)has attracted attention in photocatalytic research,particularly for its potential applications in pollutant degradation and water splitting.This layered metal oxide exhibits a narrow optical band gap of approximately 1.9 eV and can utilize most of visible light in the solar spectrum.However,the photocatalytic activity of Bi2CrO6 is relatively low,and its poor charge separation properties restrict its practical applications.Herein,we report a microwave-assisted hydrothermal method for the fabrication of Bi2CrO6 crystals with high crystallinity and uniform morphology.Compared with the conventional preparations,microwave irradiation induces rapid volumetric heating and greatly accelerates nucleation and growth reactions,forming Bi2CrO6 crystals within minutes.Multiple characterization methods,including X-ray diffraction,Raman scattering,and scanning electron microscopy,were employed to examine the crystallinity and morphologies of the samples.Microwave-assisted synthesized Bi2CrO6 crystals showed better water oxidation activity in photocatalytic and photoelectrochemical tests than the conventional samples.Oxygen evolution rates were boosted 7.2 and 3.1 times using AgNO3 and Fe(NO3)3 as electron acceptors,respectively.Further investigations showed that microwave-assisted Bi2CrO6 crystals exhibited improved photogenerated charge separation.The average lifetime of photogenerated carriers,calculated from time-resolved photoluminescence results,also showed an increase.Furthermore,using photodeposition of metals and oxides as probes,the spatial separation of photogenerated electrons and holes was demonstrated to take place between{001}top and side facets of the Bi2CrO6 crystal samples.Loading reduction and oxidation cocatalysts onto different facets significantly enhanced the photocatalytic activities.These results enforce the promise of microwave-assisted Bi2CrO6 crystal synthesis for photocatalytic water-splitting applications and present a solution for efficient solar-energy conversion.
维普
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