From plastic-waste to H2: Electrolysis of a Poly(methyl methacrylate) model molecule on polymer electrolyte membrane reactors

Hydrogen production by the electrolysis of plastic-waste was recently suggested as an alternative approach to water electrolysis, owing to its favoured thermodynamics. However, the fundamental aspects of such electro-catalytic process were not studied in detail. Here we propose a new approach to understand the electrolysis of polymers, by the use of model molecules. Our target is to develop a technology for the electrolysis of poly(methyl methacrylate), PMMA, plastic waste. We used methyl pivalate (MP) as a model molecule, since it contains similar functional groups than PMMA. We performed electrolysis experiments in a Polymer Electrolyte Membrane reactor with Nafion® protonic membranes and Pt/C electrodes at low temperatures (<90 °C). The results obtained demonstrated that the electro-oxidation of MP allows to produce H2 in a range of electrical potentials where water electrolysis is not thermodynamically possible (<1.2 V). The kinetics of this process were studied and a preliminary global mechanism was proposed to explain the electro-oxidative cleavage of this model molecule. We have clearly demonstrated that the electrolysis of a plastic-like model monomer leads to the production of hydrogen. These results could be further extrapolated in view of the practical implementation of this technology for the valorisation of PMMA waste.