Photo-thermal synergic enhancement of CoxFeAl-LDHs for hydrogen generation from hydrolysis of NaBH4

Abstract

The production of hydrogen from sodium borohydride (NaBH4) with a suitable catalyst is a promising route for the hydrogen industry. The exploration of the energy-saving catalysts with visible light response and photothermal effect is necessary for utilizing solar energy in hydrogen utilization from hydrolysis of NaBH4. In this study, a series of photo-thermal catalysts of CoxFeAl layered double hydroxides (CoxFeAl-LDHs x = 4, 6, 8) with abundant oxygen vacancy (Vo) are successfully synthesized for photo-thermal synergic catalytic H2 generation from hydrolysis of NaBH4. CoxFeAl-LDHs differ in bandgap, Vo concentration, and photo-thermal performance, with Co6FeAl-LDH show the highest concentration of Vo and most efficient photo-thermal performance under 400–700 nm irradiation. Co6FeAl-LDH can significantly lower the activation energy of the hydrolysis of NaBH4 (Ea = 35.46 kJ mol−1) and demonstrates excellent photo-thermal synergic performance with H2 generation rate of 3.38 mol g−1 h−1 without additional heat source. The mechanism study shows that the h+, ∙OH, and Vo in CoxFeAl-LDHs also play essential roles in the hydrolysis of NaBH4. This work develops a hydrotalcite-based photo-thermal synergistic catalyst, which provides a new approach for the design of sodium borohydride hydrolysis catalysts for hydrogen production.