Transition metal tuned g-C3N4 induce highly efficient photocatalytic of ammonia borane to hydrogen evolution and mechanism investigation

A highly efficient synergistic catalyst for the hydrolysis of ammonia borane to hydrogen was successfully synthesized and systematically investigated. The activity of CuNiCo/CNS can exceed some noble metal catalysts. Activity enhancement mechanism of composite photocatalyst was also thoroughly investigated through characterization techniques and DFT calculations. • The activity of CuNiCo/CNS can exceed some noble metal catalysts. • A small amount of Ni can modify CuCo alloy to obtain higher catalytic activity. • Charge polarization can greatly improve catalytic activity. • Schottky junction, LSPR and alloy effect jointly promote the catalytic activity. Ammonia borane (AB) aqueous solution can produce high purity hydrogen by catalytic hydrolysis reaction under the action of catalyst. Herein, through hydrogen bonding self-assembly method, g-C 3 N 4 atomic thin nanosheets with the thickness of 1.71 nm were prepared, and transition metal alloy nanoparticles were successfully deposited on its surface by in-situ liquid phase reduction. The TOF values of the prepared CuNiCo/g-C 3 N 4 nanosheets hydrolyzed AB with/without light irradiation are 45.1 and 28.2 respectively, and their activity even exceeds that of some noble metal catalysts. Besides, after five cycles of hydrogen production experiments, the catalytic hydrogen production decreased by less than 2 %, indicating that CuNiCo/CNS has good reusability. By forming an ultra-thin nanostructure, photogenerated electron-hole pairs can transmit faster, and the deposition of the transition metal alloy changes the orbital hybrid mode of g-C 3 N 4 , thereby changing the band structure. Cu, Ni and Co are partly involved in the composition of the valence band of g-C 3 N 4 , among which the influence of 3d orbital of Co metal is the most severe, indicating that charge polarization occurs in Co as a local electron aggregation center. In addition, the alloy effect of metal catalysis coupled with Schottky junction of photocatalytic semiconductor system and LSPR (Localized Surface Plasmon Resonance) effect of Cu metal jointly improved the synergetic activity of CuNiCo/CNS catalyst.