Among various photoinduced hydrogen gas production techniques, photochemical catalytic water splitting is promising and an ideal future energy source because of the low cost, stability, and high sustainability of the reaction system features. Aluminum oxide nanoparticles (NPS) as a photocatalyst for the splitting of water into hydrogen gas using solar energy is one of the noble missions of material science. In this work, pure aluminum oxide and L-methionine capped aluminum oxide NPs have been synthesized using the sol-gel method. The pure Al2O3 and capped Al2O3 NPs with L-methionine were investigated by Fourier transform infrared (FTIR), X-ray diffractometer (XRD), high-resolution transmission electron microscopy (HRTEM), and Zeta potential. It was found that the average particle sizes of Al2O3 NPs and capped Al2O3 NPs with L-methionine were 13 and 20 nm, respectively. L-methionine capped Al2O3 NPs had a higher negative charge with a potential of - 24.5 mV. The capping agent slightly improved the production of hydrogen from 44 to 60 ml at 75° C after 30 min under illumination.