Amine-functionalized TiO2-supported AuPd bimetallic nanoparticles for efficient photocatalytic hydrogen generation via formic acid.

Photocatalytic dehydrogenation of formic acid (FA) is a cost-effective approach to meet the ever-increasing demand for hydrogen production; however, existing catalysts often exhibit limited activity and selectivity at room temperature. In this investigation, AuPd bimetallic nanoparticles were supported on commercially available TiO₂ (P25) nanoparticles using 3-Aminopropyltrimethoxysilane (APTMS) as silane coupling agent to promote the electrostatic and covalent interactions between the catalytic noble metals and the amino groups present on the functionalized support (P25-NH₂). The prepared 2 wt% Au₁Pd₂/P25-NH₂ catalyst reached 100 % selectivity in the FA dehydrogenation reaction under full-spectrum irradiation at room temperature, exhibiting a turnover frequency (TOF) of 6058 h^-1-an eightfold enhancement compared to the unmodified Au₁Pd₂/P25 catalyst (TOF = 771 h^-1), thereby surpassing the majority of previously reported photocatalytic systems. A series of characterizations revealed three synergistic mechanisms responsible for this outstanding performance: (i) Surface amine groups adsorb and stabilize metal ions, suppressing agglomeration and achieving highly dispersed, ultrafine AuPd NPs having large surface area per volume ratio; (ii) the establishment of a Mott-Schottky junction between the support and the deposited metals enhances charge separation and directs the electrons towards the catalytic AuPd NPs; (iii) photoinduced electrons from Au are transferred to Pd through alloying, enhancing the electron density on Pd. In summary, this investigation provides a foundation for designing high-performance dehydrogenation photocatalysts, underscoring the pivotal role of surface functionalization and bimetallic alloy in optimizing catalytic architectures.