Hydrogen gas produced by electrolysis is a sustainable, eco-friendly alternative to fossil fuels. The electrochemical process liberates oxygen and hydrogen, which are both important fuels for transportation, power generation and other industrial uses. In this context graphite electrodes are an ideal platform to produce clean hydrogen at large scale.
In order to determine how well a cylindrical cathode will perform in hydrogen evolution, the surface and pore structures are crucial. Another factor that affects the electrochemical process is the presence of chemical and impurities. Various techniques have therefore been employed to improve the Hydrogen Evolution Reaction (HER).
In particular, the anodizing method has shown great promise in improving both H2O2 yields and cathode CE, by encouraging two- and even four-electron ORR. Moreover, anodizing improves the fluid resistance and increases permeability in graphite electrodes. The low surface areas of anodized GFs limit their applications in high-performance cells.
In recent years, the development of 3D porous cathodes has been a strategy that is promising to overcome limitations in 2D graphite. A number of variables, such as temperature and the inclusion of ionic active agents, can influence 3D-graphite pore size. The materials may also contain nanomaterials that enhance their reactivity when in contact with water molecules.
Due to their high surface areas and reactivity (RAC), as well their ability suppress the formations of impurities, redox actively carbons, or graphene, have gained particular attention in this context. In particular, redox active carbons have been shown to significantly increase the hydrogen generation rate of graphite cathodes by increasing their catalytic activity and enhancing the wettability of the surface.
However, the hydrogen production rates of redox active carbon-decorated graphite have been found to be lower than that of unmodified graphite. It is possible to optimize the HER efficiency on redox graphite-decorated electrodes.
It has been possible to increase the hydrogen production rate by using a grafite cathode that is micro-patterned and high in porosity. Response surface methodology (RSM), based on Box Behnken, was used to determine the optimum conditions of hydrogen production for micro-patterned electrodes. This method accurately predicted the hydrogen output rate with less that 2% error.
In comparison to electrodes commercially offered, like EN8 rods of carbon and 316 L stainless-steel, the micropatterned graphite showed greater efficiency and better hydrogen generation rate. The improvement in hydrogen evolution rate of the micro-patterned GF cathode was attributed to its larger reactive surface area and better oxygen diffusion resulting from its 3D porous structure. The graphite cathode micro-patterned has also had its conductive qualities improved through the coating of a polymer made of melamine. Melamine is able to improve the water resistance as well as the ability of the electrolyte to penetrate the pores. The polymer allows the ions through the pores in the graphite to easily pass, and thus reduces resistance between electrolyte electrode.
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