Parallelized Screening of Characterized and DFT-Modeled Bimetallic Colloidal Cocatalysts for Photocatalytic Hydrogen Evolution

Using
a newly designed and developed parallelized photoreactor
and colorimetric detection method, a large sampling of bimetallic
cocatalysts (Pd/Sn, Pd/Mo, Pd/Ru, Pd/Pb, Pd/Ni, Ni/Sn, Mo/Sn, and
Pt/Sn) for photocatalytic water reduction have been tested. Of these
cocatalysts, the combination of palladium and tin showed the highest
synergistic behavior and peak hydrogen gas production at a low relative
fraction of palladium. The resulting palladium/tin bimetallic cocatalysts
were characterized, and specifically, and scanning transmission electron
microscopy energy-dispersive X-ray spectroscopy indicated that palladium
and tin elements reside within the same particle. The experimental
catalytic activity for the palladium/tin mixture was compared to density
functional theory-derived energy values associated with the adsorption
of hydrogen onto a surface. This comparison demonstrated that the
typical peak found in electrochemical Sabatier volcano plots at ΔGH* = ∼0 eV were replicated in the experimental
photocatalytic system with a peak activity observed at ΔGH* = −0.036 eV. Computational confirmation of the results
expressed here demonstrates the efficacy of colorimetric detection
of hydrogen in parallel and presents a model for increasingly rapid
catalyst screening.