Electron Reservoir Effect of Adjacent Fe Nanoclusters Boosts Atomic Fe Active Sites on Porous Carbon for the Both Electrocatalytic Oxygen Reduction and CO 2 Reduction Reaction.

Electrochemical oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO 2 RR) are greatly significant in renewable energy-related devices and carbon-neutral closed cycle, while the development of robust and highly efficient electrocatalysts has remained challenges. Herein, a hybrid electrocatalyst, featuring axial N-coordinated Fe single atom sites on hierarchically N, P-codoped porous carbon support and Fe nanoclusters as electron reservoir (Fe NCs /Fe SAs -NPC), is fabricated via in situ thermal transformation of the precursor of a supramolecular polymer initiated by intermolecular hydrogen bonds co-assembly. The Fe NCs /Fe SAs -NPC catalyst manifests superior oxygen reduction activity with a half-wave potential of 0.91 V in alkaline solution, as well as high CO 2 to CO Faraday efficiency (FE) of surpassing 90% in a wide potential window from -0.40 to -0.85 V, along with excellent electrochemical durability. Theoretical calculations indicate that the electron reservoir effect of Fe nanoclusters can trigger the electron redistribution of the atomic Fe moieties, facilitating the activation of O 2 and CO 2 molecules, lowering the energy barriers for rate-determining step, and thus contributing to the accelerated ORR and CO 2 RR kinetics. This work offers an effective design of electron coupling catalysts that have advanced single atoms coexisting with nanoclusters for efficient ORR and CO 2 RR.