Droplet-Based Microfluidics Platform for the Synthesis of Single-Atom Heterogeneous Catalysts

Wet chemical approaches are among the most versatile and scalable strategies for preparing single-atom heterogeneous catalysts (SACs). However, despite their broad application, the synthesis of SACs via these routes remains largely ad hoc, with limited attention to the effect of different synthetic parameters on the stabilization of metal species. As a proof of concept, herein, a microfluidic platform is demonstrated for short-timescale (<10 s), systematic syntheses of SACs via wet impregnation using a range of metal precursor-carrier combinations. The microfluidic environment within rapidly mixed, nanoliter droplets ensures precise control of the concentrations and residence times of the support particles in the metal precursor solutions. This enables the rapid assessment of the influence of the metal precursor concentration on the uptake and dispersion of the adsorbed metal species, as demonstrated for the synthesis of palladium and platinum SACs based on a high-surface form of graphitic carbon nitride (C3N4). Extension to SACs based on other metals (Ni) and relevant carriers (N-doped carbon, gamma-alumina) confirms the generality of the synthesis method. The microfluidic approach opens possibilities for high-throughput parameter screening and mechanistic studies in the design of heterogeneous single-atom catalysts.

Automated summary

Wet chemical approaches are widely used for preparing single-atom heterogeneous catalysts. However, the synthesis methods lack systematic considerations of different parameters' effects. In this study, a microfluidic platform is demonstrated for rapid and systematic syntheses of single-atom catalysts using various metal precursor-carrier combinations. The microfluidic approach allows precise control of concentrations and residence times, enabling the evaluation of metal precursor concentration's influence on the adsorption and dispersion of metal species. The method is confirmed to be applicable for different metals and carriers, opening possibilities for high-throughput screening and mechanistic studies in catalyst design.