Ferrites for photoelectrochemical water splitting

用于光电化学水分解的铁氧体

• 批准号: 279116705
• 负责人: Professor Dr. Detlef Bahnemann
• 金额: --
• 依托单位: Institut für Technische Chemie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/279116705?language=en
• 关键词: Ferrites; photoelectrochemical; water; splitting

The current project aims on solar-driven hydrogen formation by photoelectrochemical water splitting employing exclusively abundant elements as electrode materials to find ecologically and economically feasible solutions for future hydrogen production. This requires the optimization of the morphology and the charge collection efficiency of the individual photo-absorber materials for hydrogen and oxygen evolution reactions. In particular, the project aims at (i) the development of ferrite, MxFe3-xO4 (M = e.g., Zn, Mg, Ca), based photoelectrodes with enhanced photoresponse utilizing template assisted electrochemical deposition, (ii) an in depth understanding of the origin and dynamics of charge carriers and reaction intermediates in ferrite based photoelectrochemical cells, and (iii) the understanding how water and hydroxide ion adsorption on the different crystallographic planes of the ferrites as well as doping and metal substitution affect their band gaps and band positions. Nanostructured ferrite based electrodes will be formed in template-assisted electrochemical deposition and via screen-printing from nanopowders obtained by different complex-, ionic liquid- and microwave-assisted sol-gel routes. The templates used in this study are small organic molecules with aromatic carboxylic acid functionality imparting porosity and/or specific crystallographic orientation during the deposition of oxide semiconductors due to preferential adsorption at certain crystal planes inducing asymmetric crystal growth. The obtained porosity and crystallographic orientation of the films will govern the photoefficiency of the electrodes. Laser flash photolysis will be used as a powerful tool to probe and elucidate the fate of reaction intermediates and charge transport. In this regard information relating to the lifetime of the charge carriers, the intermediate involved as well as their role in the water splitting reaction will be obtained for both powder and electrode samples. Based on their energetics the morphology and stoichiometry optimized ferrites will be used for photocatalytic Z-schemes and photoelectrochemical cells which will be specially designed for cost-effective water splitting and formation of pure hydrogen in a separated chamber. An integral part of this project is to gain atomic-scale understanding of the relevant processes using a systematic theoretical approach. By using first-principles methods we will elaborate the mechanisms of the surface interaction with water and OH from the solid-liquid interface on the various surface planes of ferrite electrodes. The effect of adsorption and MxNyFe3-x-yO4 composition of ternary and quaternary phases on the electronic properties (band gap and band alignment) and the surface structure will be obtained employing hybrid DFT in combination with a GW-BSE approach.

目前的项目旨在通过光电化学分解水形成太阳能驱动的氢气，使用专门的丰富元素作为电极材料，为未来的氢气生产找到生态和经济上可行的解决方案。这就需要优化单个光吸收材料的形态和电荷收集效率，以进行放氢和放氧反应。具体地说，该项目旨在(I)利用模板辅助电化学沉积开发具有增强光响应的铁氧体MxFe3-xO4(M=例如，锌、镁、钙)基光电极，(Ii)深入了解铁氧体光电化学电池中载流子和反应中间体的来源和动力学，以及(Iii)了解水和氢氧化物离子在铁氧体不同晶面上的吸附以及掺杂和金属替代对其带隙和带位的影响。通过模板辅助电化学沉积和丝网印刷从不同的络合物、离子液体和微波辅助的溶胶-凝胶路线获得的纳米粉末将形成纳米结构铁氧体基电极。本研究中使用的模板是具有芳香族羧酸官能团的小有机分子，在氧化物半导体的沉积过程中，由于在某些晶面上的优先吸附导致了不对称的晶体生长，从而提供了孔隙率和/或特定的晶体取向。得到的薄膜的孔隙率和晶体取向将决定电极的光效率。激光闪光光解将成为探索和阐明反应中间体去向和电荷传输的有力工具。在这方面，将获得有关粉末和电极样品的电荷载流子寿命、所涉及的中间体以及它们在水分解反应中的作用的信息。基于它们的能量学，优化的形貌和化学计量比的铁氧体将被用于光催化Z方案和光电化学电池，这将是专门设计的具有成本效益的水分解和在分离的室内形成纯氢气。该项目的一个组成部分是使用系统的理论方法对有关过程进行原子尺度的了解。利用第一性原理方法，我们将从铁氧体电极表面不同平面上的固-液界面上阐述与水和羟基的表面相互作用的机理。用混合密度泛函理论结合GW-BSE方法研究了三元和四元相的吸附和MxNyFe3-x-yO4组成对电子性质(带隙和能带排列)和表面结构的影响。