An electrolysis research platform with optical access at elevated temperatures and pressures

Elevated temperature operation offers a promising avenue for enabling highly efficient water electrolysers. Combined with a high operating pressure to maintain water in the liquid phase, elevated temperatures can improve reaction kinetics and ionic transport and thus further reduce the electrical energy cost for green hydrogen. However, these working conditions can make it difficult to examine bubble dynamics and their impact on electrolyser performance. This paper describes the design and construction of a novel experimental research platform for investigating water electrolysis at up to 200 bar and up to 200 °C with optical access for imaging bubble dynamics. Important design challenges are described, including the incorporation of a viewing windows as well as the reliable control of cell compression. This new, optically accessible design enables us to investigate polarisation behaviour and bubble dynamics of over a wide range of working temperatures and pressures that extend well beyond current industrial practice. • The design of a custom electrolysis setup with optical access is described. • The electrolyser allows bubble imaging at elevated temperatures and pressures. • Design elements include independent compression of the membrane and cell body. • The system's capabilities are demonstrated with electrochemical and optical data. • Results suggest non-trivial combined temperature and pressure impact on bubbles.