Boosting formic acid dehydrogenation via the design of a Z-scheme heterojunction photocatalyst: The case of graphitic carbon nitride/Ag/Ag3PO4-AgPd quaternary nanocomposites

Highlights: • A novel Z-scheme heterojunction photocatalyst, g-CN/Ag/Ag₃PO₄-AgPd, is fabricated. • Formic acid dehydrogenation is boosted by a Z-scheme heterojunction photocatalyst. • g-CN/Ag/Ag₃PO₄-AgPd provided a very high TOF of 2107 h⁻¹ in the FA dehydrogenation. The development of an efficient, eco-friendly, practical, and selective way to decompose formic acid (FA) into H₂ and CO₂ is crucial for the utilization of FA as a chemical hydrogen storage material in hydrogen economy. In this regard, photocatalytic FA dehydrogenation attracts great attention owing to its potential to meet the above-mentioned requirements. Interestingly, there is no example of heterojunction photocatalyst that tunes the hole potential of the semiconductor, resulted in a better photocatalytic activity. We report herein for the first time the design and fabrication of a novel Z-scheme heterojunction photocatalyst for FA dehydrogenation, denoted as g-CN/Ag/Ag₃PO₄-AgPd comprising graphitic carbon nitride (g-CN) and Ag₃PO₄ semiconductors, Ag and AgPd alloy nanoparticles (NPs). The designed g-CN/Ag/Ag₃PO₄-AgPd photocatalysts boosted the FA dehydrogenation by creating more positive hole potential and improving the charge separation efficiency of the two distinct semiconductors. The g-CN/Ag/Ag₃PO₄-AgPd photocatalysts provided a very high turnover frequency (TOF) of 2107 h⁻¹ in the FA dehydrogenation under white-LED illumination at 50 °C. This TOF is 3.2 times and 44 times greater than those of g-CN/AgPd and g-CN/Pd binary non-Z-scheme heterojunction catalysts, respectively, under the same conditions and comparable to the best photocatalysts and heterogeneous catalysts reported in the FA dehydrogenation so far.