Gamma irradiation assisted nickel impregnation on activated carbon derived from water hyacinth for electrocatalyst application

Abstract Water hyacinth (WH) is an invasive floating plant causing water pollution. However, its leaves contain a high cellulose content, which can be used as biomass to synthesize activated carbon. Thus, in this study, water hyacinth was subjected to the KOH activation process to obtain water hyacinth-based activated carbon (WH/AC). Moreover, as a novel method for nickel impregnation, gamma irradiation was proposed as an alternative to replacing the traditional method due to its high penetration power and energy. To obtain the optimal condition for nickel impregnation, different absorbed doses of gamma-ray (0, 20, 100 kGy) were applied to commercial activated carbon (AC), represented as 0-AC, 20-AC, and 100-AC, respectively. These samples were thoroughly characterized with BET, SEM-EDS, XRD, FTIR, and XPS. The BET surface area of commercial activated carbon increases as the absorbed dose of gamma-ray increases. The SEM images revealed that the surface morphology of the commercial activated carbon significantly changed, becoming more spherical in structure, and distributed after gamma irradiation. As a result, the optimal absorbed dose for nickel impregnation is 20 kGy. Thus, the 20 kGy absorbed dose of gamma-ray was carried out in WH/AC, yielding 20-WH/AC. From the XPS results, 20-WH/AC has a more incredible amount of nickel deposited on the surface. The activated carbon electrocatalysts were investigated for applying electrochemical carbon dioxide reduction reaction (CO2RR) by linear sweep voltammetry (LSV). Interestingly, 20-WH/AC electrocatalyst exhibited the highest CO2RR efficiency compared to others. All results indicate that water hyacinth can potentially be utilized as a raw material in producing nickel-impregnated activated carbon irradiated with gamma rays.