Investigation of a Low Temperature Hydrothermal Treatment of Metallic Copper Meshes for Electrode Surface Area Enhancement for the H2 Electrolytic Production Process

Cobus E Labuschagne

Fossil fuels are widely used as the major energy source in today’s economy despite being significant contributors to greenhouse gas emissions. Increasing levels of greenhouse gas emissions contribute to Climate Change. As governments across the globe recognise these effects and commit to reducing carbon emissions, demand for renewable energy sources increases. Hydrogen, traditionally produced by splitting water into its hydrogen and oxygen components using electrolysis, is considered a viable alternative to fossil fuels. Existing hydrogen production is costly because it uses metallic platinum electrodes. Platinum is a scarce and expensive metal and viable alternatives to platinum-based electrodes are not currently available. This project aimed to facilitate the cost-effective production of hydrogen by investigating a cheaper and more abundant material for developing a novel nanostructured electrode. It capitalised on the high-surface area of nanowires grown on copper (Cu) electrode substrates. A low temperature hydrothermal method, which used potassium hydroxide to initially form an intermediate copper hydroxide layer on the copper substrate, was used to generate copper (II) oxide (CuO) nanowires on the mesh surfaces. The chemical and physical properties and structural features of the CuO nanowires were investigated using X-ray diffraction (XRD), high temperature X-ray diffraction (HT-XRD), thermal gravimetric analysis (TGA), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and Brunauer-Emmett-Teller (BET) surface area characterisation techniques. XRD, HT-XRD, SEM-EDS, and BET results also revealed the intermediate Cu(OH)2 layer was present with the CuO nanowires. XRD results show that crystal sizes of the different phases present are in the 10 nm to 20 nm range and HT-XRD confirms that at higher temperatures only the Cu2O and CuO phases are present. Both HT-XRD and TGA results confirm the thermal stability of all the samples. SEM-EDS results illustrate that the characterised samples have various types of growth and morphologies such as agglomerated, covered, and circular areas of growth with blade, dumpling-like, rosebud-like and ring shaped structures. The sizes of these morphologies range from about 5 nm to 50 nm. Furthermore, BET confirms the surface areas of the hydrothermally prepared samples increase by about 3 times when compared to pure Cu mesh. BET also confirms the adsorption average pore diameters increased by 4 to 6 times when compared to pure Cu mesh. XRD, HT-XRD, TGA, SEM-EDS, and BET all confirmed that the surface area of the hydrothermally treated copper meshes increased when compared to the pure copper mesh. This research project adds to the growing body of knowledge on developing new electrode materials for hydrogen production in the future.

Investigation of a Low Temperature Hydrothermal Treatment of Metallic Copper Meshes for Electrode Surface Area Enhancement for the H2 Electrolytic Production Process

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