Cobalt-copper-boron doped graphitic carbon nitride as a promising catalyst for hydrogen production via sodium borohydride hydrolysis

Hydrogen (H₂) is a clean and sustainable energy source, playing a crucial role in the future and the environment. Catalysts are essential for producing H₂ via the catalytic hydrolysis of sodium borohydride (NaBH₄). Here, an effective cobalt-copper-boron-doped graphitic carbon nitride (g-C₃N₄@Co–Cu–B) catalyst was synthesized via a reduction method. This newly synthesized catalyst demonstrated high catalytic activity in the hydrolysis of NaBH₄. The structural characteristics of this catalyst were verified by AAS, XRD, SEM, EDX, TEM, FTIR, and XPS analyses. The performance of the catalyst was investigated through experiments conducted under various conditions, including the metal Co–Cu–B/(g-C₃N₄+Co–Cu–B) ratio, NaOH wt%, temperature, and reusability. As a result, the optimal metal ratio and NaOH ratio were found to be 40 wt% and 7 wt%, respectively, under the optimum conditions for the hydrolysis reaction of NaBH₄. Then, g-C₃N₄@Co–Cu–B catalyst demonstrated excellent reusability, achieving approximately 100% reaction conversion achieved in each cycle although hydrogen generation rate (HGR) values gradually decreased because of metaborate accumulation and active component degradation on the catalyst. In the studies, HGR was calculated as 6598 mlH₂ g_cat−1min−1 at 30 °C as the maximum value. When this catalyst was investigated based on nth-order kinetic model; the reaction order (n), activation energy (Ea), enthalpy change (ΔH), and entropy change (ΔS) values belonging to NaBH₄ hydrolysis reaction were found as 0.2, 42.48 kJ/mol, 39.93 kJ/mol and −166.37 J/molK respectively. Reaction rate constants (k) and Gibbs free energies (ΔG) of the reaction were also calculated as 0.00075, 0.002375, 0.003, 0.004125 (Formula presented) and 88.67, 90.34, 92, 93.67 kJ/mol for 20 °C, 30 °C, 40 °C and 50 °C respectively. Based on the results, it was deduced that using g-C₃N₄@Co–Cu–B is suitable for NaBH₄ hydrolysis.