Catalytic, Conductive Bipolar Membrane Interfaces through Layer‐by‐Layer Deposition for the Design of Membrane‐Integrated Artificial Photosynthesis Systems

In the presence of an electric field, bipolar membranes (BPMs) are capable of initiating water disassociation (WD) within the interfacial region, which can make water splitting for renewable energy in the presence of a pH gradient possible. In addition to WD catalytic efficiency, there is also need for electronic conductivity in this region for membrane-integrated artificial photosynthesis (AP) systems. Graphene oxide (GO) has been shown to catalyze WD and to be controllably reduced resulting in electronic conductivity. Layer-by-layer (LbL) film deposition has been employed to improve GO film uniformity in the interfacial region to enhance WD catalysis and through the addition of a conducting polymer in the process, add electronic conductivity in a hybrid film. Three different deposition methods were tested in order to optimize conducting polymer synthesis with oxidant in a metastable solution, and yield the best film properties. It was found that an approach including substrate dipping in a concentration of oxidant corresponding to the amount expected to incorporate into a film provides the most predictable film growth and smoothest films, as determined by UV-visible spectrometry and AFM/SEM, respectively, while dipping when the oxidant is in excess or co-spraying the oxidant and monomer produce non-uniform, heterogeneous films. These superior films are electronically conductive, producing a membrane ohmic drop of ~100 mV, which is acceptable for AP a