Jing Li

This is an extensive review on the application of thermally sprayed coatings with functional properties for electrolysers. Such coatings are critical and vital constituents (as catalysts (anode/cathode), solid electrolyte, and transport layer, including corrosion-prone parts such as bipolar plates) of the water splitting electrolysis process for hydrogen production. Thermal spray coatings have the advantage of providing thick and functional coatings from a range of engineering materials. The associated coating processes provide good control of coating thickness, morphology, microstructure, pore size and porosity, and residual strain in the coatings through selection of suitable process parameters for any coating material of interest. This review consolidates scarce literature on thermally sprayed components which are critical and vital constituents (e. g., catalysts (anode/cathode), solid electrolyte, and transport layer, including corrosion-prone parts such as bipolar plates) of the water splitting electrolysis process for hydrogen production. The research shows that there is a gap in thermally sprayed feedstock material selection strategy as well as in addressing modelling needs that can be crucial to advancing applications exploiting their catalytic and corrosion-resistant properties to split water for hydrogen production. Due to readily scalable production enabled by thermal spray techniques, this manufacturing route bears potential to dominate the sustainable electrolyser technologies in the future. While the well-established thermal spray coating variants may have certain limitations in the manner they are currently practiced, deployment of both conventional and novel thermal spray approaches (suspension, solution, hybrid) is clearly promising for targeted development of electrolysers.

Apatite-type lanthanum silicate (LSO) electrolyte is one of the most promising candidates for developing intermediate-temperature solid oxide electrolysis cells and solid oxide full cells (IT-SOECs and SOFCs) due to its stability and low activation energy. However, the LSO electrolyte still suffers from unsatisfied ionic conductivity and low relative density. Here in this work, a novel co-doped method is reported to prepare highly purified polycrystalline powders of Mg-Mo co-doped LSO (Mg/Mo-LSO) electrolytes with high excellent densification properties and improved ionic conductivity. Introducing the Mo 6+ and Mg 2+ ions into the LSO structure can increase the number of interstitial oxide ions and improve the degree of densification at lower sintering temperatures, more importantly, expand the migration channel of oxide ions to enhance the ionic conductivity. As a result, the relative density of the fabricated Mo/Mg-LSO electrolytes pellets could achieve more than 98% of the theoretical density after sintering at 1500 ℃ for 4 h with a grain size of about 1-3 μm and the EIS results showed the ionic conductivity increased from 0.782 mS·cm-1 for the pristine LSO to 33.94 mS·cm-1 for the doped sample La 9.5 Si 5.45 Mg 0.3 Mo 0.25 O 26+δ at 800 ℃. In addition, the effect of different Mo 6+ doping contents was investigated systematically, in which La 9.5 Si 5.45 Mg 0.3 Mo 0.25 O 26+δ possessed the highest ionic conductivity and relative density. The proposed Mo/Mg co-doped method in this work is one step forward in developing apatite-structured electrolytes offering excellent potential to address the common issues associated with the fabrication of dense, highly conductive, and thermochemically stable electrolytes for solid oxide electrolysers and fuel cells.