Ogawa Kanta, Abe Ryu, Walsh Aron
Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, U.K.
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.
J Am Chem Soc. 2024 Mar 6;146(9):5806-5810. doi: 10.1021/jacs.4c00150. Epub 2024 Feb 23.
Post-transition metal cations with a lone pair (sp) electronic configuration such as Pb and Bi are important components of materials for solar-to-energy conversion. As in molecules like NH, the lone pair is often stereochemically active in crystals, associated with distorted coordination environments of these cations. In the present study, we demonstrate that suppressed lone pair stereochemical activity can be used as a tool to enhance visible light absorption. Based on an orbital interaction model, we predict that a centrosymmetric environment of the cations limits the orbital interactions with anions, deactivates the lone pair, and narrows the band gap. A high-symmetry Bi site is realized by isovalent substitutions with Y by considering its similar ionic radius and absence of a lone pair. The quaternary photocatalyst BiYOX is singled out as a candidate for Bi substitution from a survey of the coordination environments in Y-O compounds. The introduction of Bi to the undistorted Y site in BiYOX results in a narrowed band gap, as predicted theoretically and confirmed experimentally. The orbital interaction controlled by site symmetry engineering offers a pathway for the further development of post-transition metal compounds for optoelectronic applications.
具有孤对（sp）电子构型的后过渡金属阳离子，如铅和铋，是太阳能转化为电能材料的重要组成部分。正如在NH等分子中一样，孤对在晶体中通常具有立体化学活性，与这些阳离子扭曲的配位环境相关。在本研究中，我们证明抑制孤对立体化学活性可作为增强可见光吸收的一种手段。基于轨道相互作用模型，我们预测阳离子的中心对称环境会限制与阴离子的轨道相互作用，使孤对失活，并缩小带隙。通过考虑其相似的离子半径和不存在孤对，用钇进行等价取代实现了高对称的铋位点。通过对Y-O化合物配位环境的研究，四元光催化剂BiYOX被选为铋取代的候选物。正如理论预测并经实验证实的那样，将铋引入BiYOX中未扭曲的钇位点会导致带隙变窄。通过位点对称工程控制的轨道相互作用为后过渡金属化合物在光电子应用中的进一步发展提供了一条途径。
