Reduced Graphene Oxide Bipolar Membranes for Integrated Solar Water Splitting in Optimal pH

The integration of light absorbers and catalysts for the water splitting process requires a membrane capable of both ion and electron management and product separation to realize efficient solar fuels systems. Bipolar membranes can maintain a pH gradient for optimal reaction conditions by the dissociation of water. Such membranes that contain graphene in the interfacial layer are fabricated by the chemical reduction of a uniformly deposited graphene oxide layer to convert sp(3) catalyst regions to sp(2) conductive regions. The resulting electrical and water dissociation properties are optimized by adjusting the exposure conditions, and treatments of less than 5 min render an interface that exceeds the conductivity requirements for integrated solar water splitting and increases the overpotential by < 0.3 V. Integration with photoelectrodes is examined by characterizing the electrical interface formed between graphene and Si microwires, and we found that efficient Ohmic junctions are possible.