Investigation on the catalytic reduction kinetics of hexavalent chromium by viral-templated palladium nanocatalysts

• The catalyst structure and activity of viral-templated Pd nanocatalysts are tunable by manipulating the synthesis conditions.
• Dichromate reduction shows size-dependent behavior, where larger Pd particles sparsely coated along TMV show higher catalytic activity.
• Pd catalyzed dichromate reduction with formic acid follows Langmuir–Hinshelwood surface reaction mechanism.
• The adsorption of formic acid on Pd surface is substantially higher than dichromate ions.

We report on examination of the dichromate reduction reaction mechanism and synthesis–structure–activity relationship of palladium (Pd) nanoparticles formed on surface-assembled viral templates. By employing Langmuir–Hinshelwood mechanism, the adsorption of formic acid on the catalytic sites is found to be substantially higher (∼300 times) than that of dichromate ions. The viral-templated Pd nanocatalysts with optimized synthesis conditions are demonstrated to have higher catalytic activity per unit Pd mass for the dichromate reduction reaction than the commercial Pd/C catalysts. The effects of catalyst synthesis conditions on the catalyst properties (i.e. Pd particle size and loading) and on the catalytic activity are also investigated via Grazing Incidence Small Angle X-ray Scattering (GI-SAXS) and reaction kinetics studies. The changes in our biotemplated nanocatalyst synthesis conditions contribute to the changes in the Pd particle size and surface loading density, leading to predictable manipulation of the catalytic activity. We expect that the new insights on the reaction kinetics and reactant adsorption behavior as well as the catalyst synthesis–structure–activity relationship reported in this work can be readily extended or applied to other catalysts and reaction systems.

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