Omusana, Simon Peter2026-10-162026-10-162026Omusana, S. P. (2026). Green synthesis of zinc oxide nanoparticles using banana pseudo stem extracts for enhanced photoelectrochemical hydrogen production. [Unpublished dissertation]. Busitema University.https://bdears.busitema.ac.ug/handle/123456789/11027DissertationZinc oxide (ZnO NPs) is among the widely studied semiconductor materials; it has shown high efficiency in photoelectrochemical (PEC) water-splitting process and photostability as well. Its performance has been slowed by a wide bandgap and fast electron-hole recombination rate, its use in PEC activity has become of great concern to scientific research. While several studies used neem and eucalyptus leaf extracts, this study used the banana pseudo stem (BPS) extracts which is cheap and is in abundance in Uganda. The ZnO NPs were fabricated by green synthesis using the BPS extract that acted as a source of the caping and stabilizing agents. Characterization of the fabricated NPs was by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), x-ray diffraction (XRD), ultraviolet-visible (UV Vis) and PEC testing that revealed high crystallinity, small crystal and particle sizes of 10 𝑛𝑚 − 20 𝑛𝑚, and 15 𝑛𝑚 − 25 𝑛𝑚 respectively with energy bandgaps ranging between 1.8 𝑒𝑉 − 2.3 𝑒𝑉. The SEM images showed higher particle agglomeration(clustering). The SEM images revealed that there were many smaller particles within the range of 5 to 15 nm, while the rest of the particles had diameters of up to between 147 nm and 156.8 nm, as evidenced in Figures 4.3 and 4.4. On computation, the mean particle diameter/size were found within 15 nm and 25 nm. On comparing the crystal sizes and particle sizes, it was realized that particle sizes were relatively greater than the crystal sizes which revealed the formation of agglomerates and clusters on the synthesized NPs. These agglomerates aided in the introduction of more active sites for enhanced PEC activities. The optimization prediction revealed that increase in both extract mass and the reaction temperatures led to formation of smaller crystal and particle size NPs with reduced energy band gaps. The compromised optimal conditions found were Mass of 9.79 𝑔, temperature of 88.0 0𝐶 producing crystal and particle sizes of 21.98 𝑛𝑚 and 21.86 𝑛𝑚, and energy bandgap of 2.075 𝑒𝑉. The PEC testing was done on all the 5 samples which revealed reducing hydrogen production as the extract masses increased. This produced photocurrent decay slope lied between 0.001 𝑚𝐴𝑠−1 𝑡𝑜 0.01 𝑚𝐴𝑠−1 which was low as compared with the expected amounts of about 1.5 𝑚𝐴𝑠−1 and this reduced value was attributed to be dominated by surface recombination and slow interfacial kinetics at the photoanode/electrolyte junction, rather than bulk transport limitations because the expected sizes of between 10 nm to 40 nm and energy bandgap of between 1.8 eV to 2.3 eV that is in the visible range had been achieved.enOther