Layer-by-layer self-assembly of palladium nanocatalysts with polyelectrolytes grafted on the polydopamine functionalized gas-liquid-solid microreactor

- A G-L-S microreactor was developed by the LBL self-assembly technique.
- A PEM thin film of PAH-PSS was grafted on the PDA functionalized surface.
- Pd nanocatalysts were synthesized on the PAH-PSS.
- The developed microreactor was evaluated by nitrobenzene hydrogenation.
- Better conversion and durability were achieved.

In this study, the layer-by-layer self-assembly technique was employed to synthesize the Pd nanocatalysts on the polyelectrolytes thin film of PAH-PSS grafted on the polydopamine functionalized surface for the development of the gas-liquid-solid microreactor. The utilization of this technique not only allows for strong adhesion of PAH-PSS on polydopamine to form a (PAH-PSS)/PDA thin film but also enables efficient adsorption of the precursor via electrostatic interactions for the nanocatalyst synthesis. The chemical composition and morphology characterizations indicated that Pd nanoparticles could be uniformly dispersed over the polyelectrolytes thin film of PAH-PSS. Experimental results on the nitrobenzene hydrogenation showed that the newly-developed microreactor with the Pd nanocatalysts deposited on the (PAH-PSS)/PDA yielded high conversion and much better durability than did the one with the Pd nanocatalysts directly coated on the PDA. Three main reasons contributed to the improved performance: (i) the increase of the catalyst loading arising from more effective precursor adsorption for synthesizing Pd nanocatalysts, (ii) the alleviation of nanocatalysts migration and agglomeration, (iii) the reduction in the adsorption of generated intermediates/by-products. Parametric studies revealed that if the supply of hydrogen was sufficient, the change of the gas flow rate showed little effect on the performance. When the liquid flow rate and inlet nitrobenzene concentration were too high, not only the conversion but also the durability were decreased. The reduction of the liquid flow rate and inlet nitrobenzene concentration led to the enhancement of the durability. This work opens a window for fabricating the high-performance gas-liquid-solid microreactors.