Construction of Z-type heterojunction by depositing CuO nanoparticles on NiO nanosheets for visible-light-enhanced catalytic ammonia borane methanolysis

The development of effective and cost-efficient catalysts for the hydrogen production through methanolysis of ammonia borane (AB) is a hot topic in the field of energy catalysis. In this study, a simple method has been developed to construct a low-cost Z-type heterojunction by depositing CuO nanoparticles on the surface of NiO nanosheets. The as-prepared CuO/NiO composites exhibit prominent activity towards AB methanolysis. The hydrogen generation rate (HGR) is 3.00 L hydrogen min 1 g cat. 1 when the optimal CuO/NiO sample functions as a catalyst, which is increased to 3.93 L hydrogen min 1 g cat. 1 with the assistance of visible light illumination. The enhancement of catalytic activity are attributed to the variation of the electronic structure of the catalysts. With the formation of Z-type heterojunction, the valence band electrons of CuO and NiO are excited and transfer to their respective conduction bands under light illumination. Subsequently, the conduction band electrons of CuO recombine with the valence band holes of NiO, leading to an accumulation of electrons at the conduction band of NiO. Consequently, the electron density of the Ni sites is increased, which enhances AB methanolysis. This study can provide new insights for the design and synthesis of cost-effective and highly efficient direct Z-type heterojunction catalysts for hydrogen production through AB methanolysis. Moreover, this study is also helpful for the understanding of how visible light enhances AB methanolysis.