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

Abstract

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 sp3 catalyst regions to sp2 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. Let's split: Reduced graphene oxide is a chemically controllable, electrically conductive catalyst for bipolar membranes in integrated photoelectrochemical water splitting. Membranes that contain graphene oxide are developed and reduced to induce electronic conductivity and maintain a sufficient catalytic activity. Upon optimization, relative overpotentials of <30% are obtained along with excellent electrical properties, and the catalysts are suited for efficient water splitting.