Introduction
In recent years, a renewed interest in electrolyzers has emerged. They
are expected to play a pivotal role in enabling the ongoing global
energy transition, as they are able to directly convert electricity into
chemical energy. Moreover, the process can be done cleanly if green
energy is used, thereby opening up the way to a sustainable chemical
industry.
A key property of an electrolyzer is its mass transfer performance. A
high mass transfer performance indicates that the reactants can quickly
reach the electrode, in this way enabling faster reactions and higher
currents. Typically, mass transfer is expressed as a Sherwood-Reynolds
correlation. In the past decades, many such correlations have been
established [1-5], but there is a large variance in the reported
mass transfer performance. For empty parallel plate electrolyzers, the
difference can be up to an order of magnitude depending on the
configuration and specific design choices that were used, such as e.g.
the design of the inlet [1]. This complicates the comparison of
results between them. Moreover, the importance of certain mass transfer
enhancing effects depends on the scale. Small-scale electrolyzers for
instance will be affected more by inlet effects than large scale cells.
Therefore, when results from a small cell are extrapolated to a larger
electrolyzer, significantly over- or underestimations can occur if these
scaling effects are not considered.
In order to increase our understanding of mass transfer in electrolyzers
more configurations need to be tested. Therein lies another complication
since most of the cells described in the literature were built in-house
or produced decades ago, resulting in them no longer being available for
present-day research. For new research, it can therefore be difficult to
find a suitable cell with known mass transfer behavior. Building new
ones is not straightforward either, as it requires design work and
complex machining. A solution to this problem is to 3D print
electrolyzers, as it allows the quick construction of numerous
prototypes.
The purpose of this work is to carry out a systematic investigation into
electrolyzer mass transfer performance. 3D printed parallel plate
electrolyzers are used to investigate the effects of different inlet
designs, inlet lengths, and turbulence promoters and results are
compared to previous work.