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

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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.