混合原子尺度电子组态作为高熵氧化物光催化中避免使用助催化剂的策略
Mixed atomic-scale electronic configuration as a strategy to avoid cocatalyst utilization in photocatalysis by high-entropy oxides
AI总结：
本研究提出混合异质电子组态与不同电负性元素以提供电子受/给体位点的策略，设计合成新型双相高熵氧化物TiZrNbTaGaO₁₀.₅，实现无贵金属助催化剂下的CO₂转化与水分解制氢，为无辅助剂光催化剂设计提供新准则。
摘要：
为提升制氢和CO₂转化用光催化剂的活性，通常会使用铂、金等贵金属助催化剂作为电子陷阱和/或受体。本研究假设，将具有异质电子组态和不同电负性的元素混合，可同时提供电子受体位点和给体位点，从而避免使用助催化剂。该假设在高熵氧化物（HEOs）中得到验证，这类材料可在保持单相或双相结构的同时，实现原子尺度组成的高度灵活调控。研究设计并合成了一种新型高熵氧化物，其混合了具有空d轨道的元素（钛、锆、铌、钽）和具有全满d轨道的元素（镓）。该氧化物通过高压扭转结合煅烧工艺合成，包含两相（88 wt%正交晶系（Pbcn）和12 wt%单斜晶系（I2/m）），整体组成为TiZrNbTaGaO₁₀.₅。它具有紫外和可见光吸收能力，带隙低至2.5 eV，且由于阳离子的混合价态，表现出低辐射电子-空穴复合率和氧空位生成特性。在无需添加助催化剂的情况下，该氧化物成功作为光催化剂实现了CO₂转化生成CO和CH₄，以及水分解制氢。这些研究结果证实，引入异质电子组态和电负性可作为避免使用助催化剂的设计准则。
英文摘要：
To enhance the activity of photocatalysts for hydrogen production and CO2 conversion, noble metal cocatalysts as electron traps and/or acceptors such as platinum or gold are usually utilized. This study hypothesizes that mixing elements with heterogeneous electronic configurations and diverse electronegativities can provide both acceptor and donor sites of electrons to avoid using cocatalysts. This hypothesis was examined in high-entropy oxides (HEOs), which show high flexibility for atomic-scale compositional changes by keeping their single-or dual-phase structure. A new highentropy oxide was designed and synthesized by mixing elements with an empty d orbital (titanium, zirconium, niobium and tantalum) and a fully occupied d orbital (gallium). The oxide, synthesized by high-pressure torsion followed by calcination, had two phases (88 wt% orthorhombic (Pbcn) and 12 wt% monoclinic (I2/m)) with an overall composition of TiZrNbTaGaO10.5. It exhibited UV and visible light absorbance with a low bandgap of 2.5 eV, low radiative electron-hole recombination and oxygen vacancy generation due to mixed valences of cations. It successfully acted as a photocatalyst for CO and CH4 production from CO2 conversion and hydrogen production from water splitting without cocatalyst addition. These findings confirm that introducing heterogeneous electronic configurations and electronegativities can be considered as a design criterion to avoid the need to use cocatalysts.
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