Highly efficient porous electrodes of nanocrystalline metal-metalloid-powder coatings through short-time sintering

碱法电解水被认为是实现无碳能源循环规模化制氢的关键技术。为了提高这些设施的效率，从而提高其经济性，需要不断地进一步开发所有系统部件，特别是电极材料及其生产工艺。在这方面，高效率的电极需要良好的机械稳定性，良好的多孔样品表面以及高的本征电催化活性。后一种要求可以通过合适的化学成分和表现出高密度表面缺陷的纳米晶态来获得。特别是添加了Co、Mo、Si、B等添加剂的非晶态和纳米晶Fe-Ni基合金表现出了良好的电催化活性。在这方面，短时烧结技术--放电等离子烧结(SPS/FAST)可用于制造纳米金属半成品，节省时间和资源。此外，由于具有较高的活性表面积和对气泡的优化管理，粗糙和多孔表面提高了电极的效率。在这个DFG项目中，计划利用SPS/FAST技术来制备具有多孔和纳米晶结构的薄层涂层，这些涂层结合在金属衬底上。这提供了根据要实现的应用来实现高效的气体发生电极的机会。由具有一定厚度和孔隙率的纳米晶金属-类金属粉末组成的电催化活性涂层将结合纳米晶材料和粗糙、多孔表面结构的优点，并具有良好的机械稳定性。重点将是更好地了解基质金属氧化物涂层的短期烧结行为和结构性能的演变(颗粒尺寸、气孔率、相形成和烧结颈的形成)，这将通过系统地改变烧结参数(压力、温度、升温速度和保温时间)来研究。此外，还将评估涂层与基材之间界面的机械稳定性。在此基础上，研究了烧结的基质金属氧化物涂层基质复合材料的电催化活性和长期稳定性与基质金属氧化物涂层结构性质的关系。根据基质-基质复合材料的结构-性能关系，将得出对可持续水电解高效、长期稳定的电极材料，以及其他产气的电化学过程有价值的结论。

The alkaline electrolysis of water is considered as a key technology for the hydrogen production at large-scale to fulfill a carbon-free energy circle. In order to enhance the efficiency and thereby the economy of such facilities, the consistent further development of all system components and, in particular, the electrode materials and their production processes are needed. In this regard, highly efficient electrodes require a good mechanical stability, a well-defined porous sample surface as well as a high intrinsic electrocatalytic activity. The latter requirement can be obtained by a suitable chemical composition and a nanocrystalline state which exhibits a high density of surface defects. Particularly, amorphous and nanocrystalline Fe- and Ni-base alloys with additives of Co, Mo, Si, B show excellent electrocatalytic activity. In this regard, the short-time sintering technology, spark plasma sintering (SPS/FAST), can be used to manufacture nanocrystalline metallic semi-finished products by saving time and resources. Furthermore, it is established that rough and porous surfaces improve the efficiency of the electrode due to a high active surface area and an optimized management of gas bubbles.In this DFG-project it is planned to utilize the SPS/FAST technology for thin layer coatings with a porous and nanocrystalline structure, which are bonded on a metallic substrate. This offers the opportunity to realize highly efficient, gas-generating electrodes in accordance with the application to be fulfilled. Electrocatalytic active coatings which consist of nanocrystalline metal-metalloid-powders (MMP) with a defined thickness and porosity will be synthesized, which shall combine the advantage of nanocrystalline materials and rough, porous surface structures together with a good mechanical stability. The focus will be the better understanding of the short-time sintering behavior and the evolution of the structural properties of the MMP-coating (grain size, porosity, phase formation and formation of sintering necks), which will be investigated by a systematic variation of the sintering parameters (pressure, temperature, heating rate and holding time). Furthermore, the mechanical stability of the interface between the coating and substrate will be evaluated. Based on this, the electrocatalytic activity as well as the long-term stability of the sintered MMP-coating-substrate-composite in dependence on the structural properties of the MMP-coating will be investigated. From the structural-properties relationship of the MMP-substrate composites valuable conclusions for highly efficient and long-term stable electrode materials for sustainable water electrolysis but also for other electrochemical processes of gas production will be deduced.