Facile synthesis of single-atom electrocatalysts with tailored carbon architectures via a polyelectrolyte brush-templated-growth approach

ZIF-8-derived single atom catalysts (SACs) have been widely reported and show prospects for various electrocatalytic reactions. In addition to the coordination environments of the single atoms, the geometric shape and morphology of ZIF-8 also affect the catalytic performances, which is somewhat unnoticed and not studied thoroughly at the current stage. Herein, we report a polyelectrolyte brush-templated-growth approach to synthesize ZIF-8-derived SACs with different hollow carbon nanoarchitectures. An anionic spherical poly(acrylic acid) brush (PAA-SPB) with a highly negatively charged polyelectrolyte brush layer is rationally designed and used to grow ZIF-8 nanocrystals in situ via a spatial confinement strategy. Such an approach is verified for the synthesis of Fe, Co, Cu, and Pd single-atom catalysts, respectively. In particular, the as-synthesized Fe single-atom catalysts are used to highlight the advantages of this synthetic approach, realizing superior oxygen reduction reaction (ORR) performance and outperforming the benchmark Pt/C. The morphology and structure of a ZIF-8-derived carbon matrix based on PAA-SPB and its effect on the ORR performance are studied intensively. It is revealed that more Fe single atom active sites are exposed, while the mass transfer in the electrochemical process is promoted via the elaborate tuning of carbon architectures. This work provides a new synthetic strategy that is facile, controllable, and general for achieving the delicate design of the high-performance single-atom catalysts from the aspect of the supports.