Pushing the Limits of Metastability in Semiconducting Perovskite Oxides for Visible-Light-Driven Water Oxidation
Pushing the Limits of Metastability in Semiconducting Perovskite Oxides for Visible-Light-Driven Water Oxidation
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DOI：
10.1021/acs.chemmater.0c00044
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发表时间：
2020-04-14
影响因子：
8.6
通讯作者：
Maggard, Paul A.
中科院分区：
文献类型：
--
作者：
O'Donnell, Shaun;Chung, Ching-Chang;Maggard, Paul A.
人们已经发现了一条合成热力学不稳定的亚稳态钙钛矿氧化物的途径，这种氧化物作为无铅介质和小禁带半导体受到了极大的追捧。用低熔点的SnCl2/SnF2包晶助熔剂，得到了A位(Ba1-XSnX)和A位和B位(Ba1-XSnX)(Zr1-yTiy)O-3混合固溶体，具有很高的亚稳性，锡(II)阳离子含量高达60%，计算出分解反应能高达-0.3 eV原子(-1)。含Zr(IV)的钙钛矿型化合物和混合的Zr(IV)/Ti(IV)阳离子具有较高的结合能，从而实现了较高的Sn(II)浓度的动力学稳定。随着掺锡量的增加，能带显著红移，使光学吸收边从接近3.90 eV宽调谐到接近1.95 eV。对于含>；12.5%Sn(II)和>；25%Ti(IV)阳离子的BSZT组合物，计算了渗流路径。对于超过渗流阈值的化合物，发现高的光催化生成分子氧的速率，其中扩展的扩散路径应该在整个结构中“打开”，电荷载流子变得离域而不是被捕获。这些结果确立了合成访问亚稳态半导体对于发现先进的光学和光催化性能的关键重要性。
A synthetic route has been discovered to thermodynamically unstable, i.e., metastable, Sn(II)-perovskite oxides that have been highly sought after as lead-free dielectrics and small bandgap semiconductors. A highly facile exchange of Sn(II) is found by using a low melting SnCl2/SnF2 peritectic flux, yielding mixed A-site (Ba1-xSnx)ZrO3 and mixed A- and B-site (Ba1-xSnx)(Zr1-yTiy)O-3 solid solutions that exhibit a very high metastability, with up to 60% Sn(II) cations and a calculated reaction energy for decomposition of up to -0.3 eV atom(-1). Kinetic stabilization of the higher Sn(II) concentrations is achieved by the high cohesive energy of the perovskite compositions containing Zr(IV) and mixed Zr(IV)/Ti(IV) cations. Significantly red-shifted bandgaps are found with increasing Sn(II) substitution, enabling the optical absorption edge to be broadly tuned from similar to 3.90 to similar to 1.95 eV. Percolation pathways are calculated to occur for BSZT compositions with >12.5% Sn(II) and >25% Ti(IV) cations. High photocatalytic rates are found for molecular oxygen production for compositions which exceed the percolation thresholds, wherein extended diffusion pathways should "open up" across the structure and the charge carriers become delocalized rather than trapped. These results establish the critical importance of synthetically accessing metastable semiconductors for the discovery of advanced optical and photocatalytic properties.