High catalytic activity of cobalt nanoparticles synthesized by ultrasonic spray method in sodium borohydride hydrolysis

Enhancing the hydrolysis reaction of NaBH₄ for efficient hydrogen production requires the development of effective catalysts. In this study, the solution particles used for nanoparticles synthesized using the ultrasonic spray (US) method were produced for the first time in N₂ at room temperature in the gas and liquid intermediate phases. It also brings a new approach to synthesizing low-cost and efficient catalysts using ultrasonic spray technology. The proposed method involves US the CoCl₂ solution into the NaBH₄ solution to reduce cobalt, producing catalysts for hydrogenation. This innovative approach pioneers a gas-liquid interface reaction for metal reduction. The resulting catalysts were characterized using SEM, XRD, XPS, TEM, BET and FT-IR analysis. The influence of NaOH/NaBH₄ concentration, solution temperature, and catalyst amount on hydrogen production rate was investigated, and kinetic parameters were analyzed to understand the reaction kinetics better. The hydrogen production rates of US-Co and reduction method (RM) Co catalysts under the same conditions were calculated as 3995 ml_H2/min.g_cat and 1245 ml_H2/min.g_cat, respectively. The activation energy values calculated for the NaBH₄ hydrolysis of the US-Co catalyst using the nth-order and Langmuir-Hinshelwood kinetic models are 46.75 kJ/mol and 46.87 kJ/mol, respectively. Therefore, it can be concluded that the Langmuir-Hinshelwood kinetic model is consistent with the nth-order kinetic model. Experimental results showed that the ultrasonic spray method is very effective in producing active metal catalysts, offering promising opportunities for catalytic advances.