Hydrogen production by water splitting using commercial Al pellets in a circulating NaOH flow reactor

The production of heat and hydrogen gas by water splitting was experimentally investigated in a circulating flow reactor. Aluminum (Al) alloy pellets (i.e., AA6061; 10 mm long and 0.5 mm in diameter) and aluminum beverage can scraps (10 mm wide by 10 mm long and 0.24 mm thick) were used as the energy source, while sodium hydroxide (NaOH; 98 % purity) pellets were used to make aqueous alkali solutions. The temperature, mass flow rate, and molar concentration of NaOH solutions were varied in the range of 25 ∼ 85 ℃, 4.4 ∼ 21.4 g_sol/s, and 1 ∼ 4 M_NaOH, respectively, to conduct a parametric study. The experimental results showed an increase in hydrogen (H₂) production rate with increasing solution temperature and NaOH molar concentration, whereas the H₂ evolution rate was not reduced significantly with increases in the amount of AA6061 pellets charging the reactor or the mass flow rate of the NaOH solution. From the one-cycle operation results, the average heat generation rate and hydrogen production rate for AA6061 pellets and aluminum beverage can scraps were 3.26 Wh_th/g_AA6061, 2.06 Wh_th/g_Alcan, 3.54 Wh_H2/g_AA6061, and 2.72 Wh_H2/g_Alcan, respectively. Generation of a combination of heat and power for next-generation district heating was deemed possible using the combination of common AA6061 pellets, Al beverage can scraps, and aqueous NaOH solutions in a circulating flow reactor.