Interface engineering via temperature-dependent self-transformation on SnS2/SnS for enhanced piezocatalysis

通过温度依赖性自转化在SnS_2/SnS上进行界面工程以增强压电催化

Heterojunction has been widely used in vibration-driven piezocatalysis for enhanced charges separation,while the weak interfaces seriously affect the efficiency during mechanical deformations due to prepared by traditional step-by-step methods.Herein,the intimate contact interfaces with shared S atoms are ingeniously constructed in SnS_(2)/SnS anchored on porous carbon by effective interface engineering,which is in-situ derived from temperature-dependent self-transformation of SnS_(2).Benefiting from intimate contact interfaces,the piezoelectricity is remarkably improved due to the larger interfacial dipole moment caused by uneven distribution of charges.Importantly,vibration-induced piezoelectric polarization field strengthens the interfacial electric field to further promote the separation and migration of charges.The dynamic charges then transfer in porous carbon with high conductivity and adsorption for significantly improved piezocatalytic activity.The degradation efficiency of bisphenol A(BPA)is 6.3 times higher than SnS_(2) and H2 evolution rate is increased by 3.8 times.Compared with SnS_(2)/SnS prepared by two-step solvothermal method,the degradation efficiency of BPA and H2 evolution activity are increased by 3 and 2 times,respectively.It provides a theoretical guidance for developing various multiphase structural piezocatalyst with strong interface interactions to improve the piezocatalytic efficiency.

构建异质结是提高半导体催化剂中电荷分离效率的一种有效方法.并且,接触界面由于晶格失配容易引起电荷再分配,从而有利于增强极性,有望在调控压电性质方面发挥独特的优势.更重要的是,异质结通常需要高质量的界面,以便实现载流子的高效空间分离.然而,大多数异质结是通过传统的物理混合、两步水热/溶剂热或逐步沉积方法制备的,这些方法不利于形成紧密接触的界面,从而限制了电荷传递效率.鉴于SnS_(2)的温度依赖性相结构转变特性,本文提出了一种原位自转化策略来构建具有强相互作用的高质量界面,并协同吸附效应共同提升压电催化活性.首先将SnS_(2)纳米片锚定在ZIF-8衍生多孔碳(ZNC)表面,然后通过调控退火温度巧妙地原位合成了一系列相结压电催化剂(ZNC@SnS_(2)/SnS).通过扫描电镜和透射电镜观察了ZNC表面SnS_(2)纳米片在高温退火过程中的形貌变化,实验发现,随着退火温度升高纳米片逐渐倾斜并减小,最终形成板状的SnS.X射线粉末衍射和拉曼光谱结果表明,SnS_(2)向SnS转化的程度随退火温度升高而逐渐增大,500℃时SnS_(2)完全转化为SnS.X射线光电子能谱结果表明转化过程中Sn元素的化合价逐渐由Sn~(4+)转变为Sn~(2+),相结因存在Sn…S…Sn键而利于形成紧密接触的界面.氮气等温吸附脱附曲线结果表明,450℃退火得到的样品(450-SZNC)具有最大的比表面积.压电催化性能评价结果表明,450-SZNC表现出最佳的催化活性和良好的稳定性,对水中低浓度BPA的降解效率是SnS_(2)的6.3倍,其催化还原分解水析出H_2的速率是SnS_(2)的3.8倍.此外,原位自转化法制备的SnS_(2)/SnS_(2)对BPA的降解效率和H_2的析出速率分别是两步溶剂热法制备的SnS_(2)/SnS的3倍和2倍,压电力显微镜测试结果表明,450-SZNC表现出最高的压电响应.采用开尔文探针力显微镜、压电电流强度曲线和电化学阻抗曲线研究了催化剂的载流子分离效率.进一步通过紫外-可见漫反射光谱、莫特肖特基曲线和紫外光电子能谱分析了SnS_(2)/SnS异质结界面的电荷传输行为,界面之间存在从SnS_(2)指向SnS的内建电场,与机械振动下形成的极化电场协同促进载流子的分离与迁移.最后,借助密度泛函理论计算从理论层面分析了SnS_(2)/SnS异质结的界面相互作用和电荷转移机制.界面处键长和键角的显著波动导致电荷分布不均,从而增加了极性.在内建电场作用下,电子主要聚集在SnS_(2)上,而空穴主要聚集在SnS中.在应力作用下,界面处通过Sn-S键进行了大量的电荷转移和交换,更多的电子聚集在SnS_(2)上,更多的空穴留在SnS中,这得益于应力诱导的内部极化电场和界面电场的协同作用.综上,原位自转化的界面工程可以构筑紧密接触的高质量界面,有效提高SnS_(2)的压电催化活性,为原位合成各种多相结构压电催化剂提供了一种简单、低成本和高效的策略,并为研究相结构界面相互作用对压电催化的影响提供了理论参考。