Lone but Not Alone: Precise Positioning of Lone Pairs for the Design of Photocatalytic Architectures
Lone but Not Alone: Precise Positioning of Lone Pairs for the Design of Photocatalytic Architectures
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DOI：
10.1021/acs.chemmater.1c03762
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发表时间：
2022-01-31
影响因子：
8.6
通讯作者：
Banerjee, Sarbajit
中科院分区：
文献类型：
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作者：
Handy, Joseph, V;Zaheer, Wasif;Banerjee, Sarbajit
当前的经济增长和消费趋势预计将导致全球气温急剧上升，世界正处于气候变化的十字路口。未来十年化石燃料、工业和土地使用产生的温室气体排放量的减少速度将决定本世纪剩余时间全球变暖的轨迹。越来越明显的是，交通基础设施的深远脱碳需要辅之以广泛的碳捕获、储存和利用。借鉴大自然的经验，光催化结构可以利用水或二氧化碳以及从阳光中收集的能量，并将其以能量密集的化学键的形式存储，这是一个有吸引力的主张。利用太阳辐照度，通过涉及光伏发电的太阳能转换，以及太阳能燃料的光催化发电和二氧化碳的光催化还原已成为能源转型的紧迫任务。功能性光催化剂必须能够有效吸收阳光，有效分离电子空穴对，并确保它们以适当的电位传递到催化位点以介导氧化还原反应。这种光催化结构必须进一步引导氧化还原事件沿着特定的途径产生所需的产物，并确保反应物在催化位点之间的传输；所有这些都具有高效率和最小的退化。在本视角中，我们描述了一系列异质结构，旨在促进稳健和高效的直接太阳能驱动的水分解和二氧化碳减排。异质结构包含M(x)V(2)O(5)或MxMy'V2O5，其中M是p区阳离子，M'是s区、p区或d区阳离子，并且V2O5代表与半导体量子点(QD、二元或三元II-VI或III-V QD)界面连接的该组合物的多种多晶型物之一。 M(x)V(2)O(5) 中 p 区阳离子的立体化学活性 5/6s(2) 电子孤对产生位于 O 2p 衍生价带上方的填充中带隙电子态。在异质结构中，QD 的光激发导致空穴在亚皮秒时间尺度上转移到 M(x)V(2)O(5) 或 MxMy'V2O5 的中带隙态。超快电荷分离最大限度地减少了量子点的光阳极腐蚀，这在历史上一直是其在光催化中使用的主要障碍，并使得电荷传输和随后支撑光催化的氧化还原反应能够与电子空穴复合竞争。孤对电子态的能量定位和色散可通过 M(x)V(2)O(5 ) 或 MxMy'V2O5 化合物调色板中的多种化学和成分杠杆进行调节：孤对阳离子 M 及其化学计量 x 的选择、V2O5 多晶型物的原子连通性、“四元”氧化钒青铜中 M' 阳离子的共插、阴离子取代以及替代的孤对钒酸盐框架参考硬X射线光发射、晶体轨道哈密顿布居分析和光谱电化学特征，讨论了理解孤对态本质的设计原理。量子点的尺寸、成分和掺杂以及界面结构为异质结构集成提供了额外的杠杆，能够调节热力学能量偏移和电荷转移动力学，这些已经在几代异质结构中进行了系统优化，以提高光催化性能。描述了制备新的孤对电子 M(x)V(2)O(5) 或 MxMy'V2O5 化合物的合成策略及其在异质结构中的整合。鉴于变量数量众多，我们还讨论了机器学习和高通量合成在解决高维材料设计问题方面的适用性前景。
With current economic growth and consumption trends projected to bring about a precipitous and rapid rise of the global temperature, the world stands at a crossroads with regards to climate change. The rate at which greenhouse gas emissions from fossil fuels, industry, and land-use is curtailed over the next decade will determine the trajectory of global warming for the rest of the century. It is increasingly apparent that far-reaching decarbonization of the transportation infrastructure will need to be supplemented by extensive carbon capture, storage, and utilization. Taking a leaf from Nature's playbook, photocatalytic architectures that can utilize water or CO2 in conjunction with energy harvested from sunlight and store it in the form of energy-dense chemical bonds represent an attractive proposition. Harnessing solar irradiance, through solar energy conversion involving photovoltaics, as well as the photocatalytic generation of solar fuels, and the photocatalytic reduction of CO2 have emerged as urgent imperatives for the energy transition. Functional photocatalysts must be capable of efficiently absorbing sunlight, effectively separating electron-hole pairs, and ensuring they are delivered at appropriate potentials to catalytic sites to mediate redox reactions. Such photocatalytic architectures must further direct redox events down specific pathways to yield desired products, and ensure the transport of reactants between catalytic sites; all with high efficiency and minimal degradation. In this Perspective, we describe a palette of heterostructures designed to promote robust and efficient direct solar-driven water splitting and CO2 reduction. The heterostructures comprise M(x)V(2)O(5 )or MxMy'V2O5, where M is a p-block cation, M' is an s-, p-, or d-block cation, and V2O5 represents one of multiple polymorphs of this composition interfaced with semiconductor quantum dots (QDs, binary or ternary II-VI or III-V QDs). The stereochemically active 5/6s(2) electron lone pairs of p-block cations in M(x)V(2)O(5 )give rise to filled midgap electronic states that reside above the O 2p-derived valence band. Within heterostructures, the photoexcitation of QDs results in the transfer of holes to the midgap states of M(x)V(2)O(5 )or MxMy'V2O5 on subpicosecond time scales. Ultrafast charge separation minimizes the photoanodic corrosion of QDs, which has historically been a major impediment to their use in photocatalysis, and enables charge transport and the subsequent redox reactions underpinning photocatalysis to compete with electron-hole recombination. The energy positioning and dispersion of lone pair states is tunable through multiple chemical and compositional levers accessible across the palette of M(x)V(2)O(5 )or MxMy'V2O5 compounds: choice of lone-pair cation M and its stoichiometry x, atomic connectivity of V2O5 polymorphs, cointercalation of M' cations in "quaternary" vanadium oxide bronzes, anionic substitution, and alternative lone pair vanadate frameworks with altogether different compositions and lattice structures.Design principles for understanding the nature of lone pair states are discussed with reference to hard X-ray photoemission, crystal orbital Hamiltonian population analyses, and spectroelectrochemical signatures.The dimensions, composition, and doping of QDs along with interfacial structure afford additional levers for heterostructure integration, enabling tuning of thermodynamic energy offsets and charge-transfer dynamics, which have been systematically optimized across several generations of heterostructures to improve photocatalytic performance. Synthetic strategies to prepare new lone-pair M(x)V(2)O(5 )or MxMy'V2O5 compounds and their integration within heterostructures are described. Given the large number of variables, we also discuss prospects for the applicability of machine learning and high-throughput synthesis to tackle high-dimensional materials design problems.