Streamlining Electrode Optimization for Sustainable Organic Electrohydrogenation

Electrochemical hydrogenations are becoming increasingly important in today’s world, representing a gateway reaction for the sustainable production of base and fine chemicals. However, finding optimal reaction conditions for such systems can be challenging due to a vast variety of adjusting screws that influence the overall performance of the reactor. Especially the tailored electrode fabrication is one of the most complex, but also most important parts of scalable electrochemical cells. Combining catalyst and binder materials, and optimizing their subsequent deposition are critical steps in the electrode fabrication process and have a significant impact on the final electrode performance. For the deposition of the catalyst, a suitable coating technique, catalyst substrate and catalyst loading must be found to provide an optimal hydrogenation environment. However, the complex interplay of all these process variables of the electrode fabrication can make an optimal electrode design very challenging. We herein present a coherent workflow that allows for a fast and accurate optimization of electrodes for the electrochemical hydrogenation, with well-adjustable experimental effort. The approach covers the selection of catalyst-binder combinations, layer deposition methods, electrode substrates and catalyst loadings. To determine the influence and interplay of these fabrication parameters, the performance of the electrodes was tested in the hydrogenation of phenylacetylene to styrene as a model reaction with a selection of earth-abundant metal sulfides of the pentlandite class. For this, we employed an in-house built zero-gap electrolyser that can operate at industrially relevant current densities and low cell voltages. Special focus is laid on the evaluation of the electrochemical performance and post-mortem analyses of the catalytic layers to detect changes in catalyst structure after electrolysis. Our findings show that rapid optimization of tailored electrodes is possible with reasonable experimental effort and that understanding the interplay of the electrode fabrication variables will ease the way towards establishing industrial electrochemical hydrogenations. Figure 1