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 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.

Selectivity of Transport Processes in Ion-Exchange Membranes: Relationship with the Structure and Methods for Its Improvement

“…Due to their high selectivity, they have been successfully used in a number of applications. Very interesting is the recently discovered possibility to convert sunlight into ionic electricity with bipolar membranes [ 283 ] and to apply this energy for CO 2 reduction [ 284 ] and for water electrolysis [ 285 , 286 , 287 , 288 , 289 , 290 , 291 , 292 ]. The use of bipolar membranes is also advantageous in reverse electrodialysis [ 293 ] and in storage of electrical energy using flow batteries [ 294 ].…”

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

“…In‐house BPMs were fabricated by using a method similar to that previously described . LbL‐modified (and unmodified) anion‐exchange membranes (4×4 cm) were fastened to glass substrates by using electrical tape.…”

“…One previous approach innovates the GO‐BPM for this purpose by controllably reducing GO (rGO) postdeposition, which restores some sp 2 ‐carbon character and, therefore, some conductive properties to graphene while leaving some catalytic functional groups . The catalytic/conductor component tradeoff can be optimized by adjusting the chemical reduction conditions.…”

Bipolar Membranes to Promote Formation of Tight Ice‐Like Water for Efficient and Sustainable Water Splitting

“…[20] Since then, extensive efforts have continued to improve the water dissociation capability of GO via modification of the oxidation state, the coating method, and the surface functionality of GO. [21,22] To maximally enhance BPM catalytic activity, a planar composite catalytic structure consisting of 2D GO decorated with high-performance nanoparticular catalysts could provide the geometrical advantage of a 2D structure with intrinsically excellent catalytic reactivity. Also, molecular-level analyses of the catalytic performance of such materials that would elucidate the effects of the various catalytic actions on the water dissociation kinetics should be accompanied to develop optimized configurations of BPMs eventually.…”

“…[ 20 ] Since then, extensive efforts have continued to improve the water dissociation capability of GO via modification of the oxidation state, the coating method, and the surface functionality of GO. [ 21,22 ]…”