Graphite/RGO coated paper μ-electrolyzers for production and separation of hydrogen and oxygen

Microfluidic electrolyzers have been fabricated using graphite coated paper electrodes to electrolyze sea water into oxygen (O-2) and hydrogen (H-2) when integrated with a photovoltaic (PV) cell. The 'open' electrolyzer (OME) consists of a microchannel confined by a pair of graphite electrodes, which is drawn with the help of pencil tips. A sea water microdroplet has been dispensed at the junction of the electrodes while the PV cell is integrated to the electrodes to supply current. The microscale width of channel generates a high intensity electric field even at a lower potential, which facilitates the microdroplets to electrolyze into H-2 and O-2 near the cathode and anode. The rate of production of the gases increased with field intensity. In the 'close' electrolyzer (CME), the paper decorated with graphite electrodes is covered with a substrate embedded with polymeric microchannels. The microcapillaries are placed closer to the anode and cathode for in situ separation of H-2 and O-2. The economic, flexible, and metal-free microelectrolyzer facilitates the water-splitting at a much lower applied voltage at an efficiency of 1-2%. Use of multiple separation channels in CME for production and separation of H-2 and O-2 shows the potential for micro-very-large-scale-integration (mu-VLSI). (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Microfluidic electrolyzers using graphite coated paper electrodes were successfully fabricated for electrolyzing sea water into hydrogen and oxygen. Integration of PV cells with graphite electrodes allowed for efficient electrolysis at a lower potential, while microchannels and microcapillaries enabled in situ separation of H-2 and O-2.