High-throughput screening system for catalytic hydrogen-producing materials

A high-throughput screening system and methodology were developed for libraries of hydrogen (H-2) producing catalytic materials. The system is based on the chemo-optical properties Of WO3, which give rise to reflectance changes in the presence of H-2. Pd-coated WO3 sensors were synthesized and examined for their hydrogen sensitivity, wavelength-dependent reflectance, and performance in the presence of water vapor. For high-throughput screening, a polypropylene reactor block was designed and constructed to house 8 x 12 catalyst libraries deposited as thin films. When the library and reactor block are assembled together, 96 independent microreactor units are formed. A large-area Pd/WO3 sensor film covers and seals all microreactors, forming a 96-element 2-D H-2 sensor array. As H-2 is produced differentially across the library, the reflectance changes of the Pd/WO3 film are monitored by reflectivity sensors that scan the surface every 30 s. The time-dependent changes in reflectance indicate relative rates of H-2 production. A library of cathode electrocatalysts was synthesized from Ti, Pt, Ni, Au, Pd, Al, Ag, Ge, and mixtures thereof to demonstrate the H-2 high-throughput screening system. The results of the electrolytic screening are in agreement with expected literature trends: mixtures of Ni and samples containing Pt and Pd generated H2 at the greatest rates, while Ge- and Ti-based materials were the least effective electrocatalysts. A mixture of 80% Al and 20% Pt was found to have the highest rate of H-2 production. This high-throughput screening system is applicable in a variety of catalytic screening applications where hydrogen is the desired product.