Deep Electronic State Regulation through Unidirectional Cascade Electron Transfer Induced by Dual Junction Boosting Electrocatalysis Performance.

Unidirectional cascade electron transfer induced by multi-junctions is essential for deep electronic state regulation of the catalytic active sites, while this advanced concept has rarely been investigated in the field of electrocatalysis. In the present work, a dual junction heterostructure (FePc/L-R/CN) is designed by anchoring iron phthalocyanine (FePc)/MXene (L-Ti 3 C 2 -R, R═OH or F) heterojunction on g-C 3 N 4 nanosheet substrates for electrocatalysis. The unidirectional cascade electron transfer (g-C 3 N 4 → L-Ti 3 C 2 -R → FePc) induced by the dual junction of FePc/L-Ti 3 C 2 -R and L-Ti 3 C 2 -R/g-C 3 N 4 makes the Fe center electron-rich and therefore facilitates the adsorption of O 2 in the oxygen reduction reaction (ORR). Moreover, the electron transfer between FePc and MXene is facilitated by the axial Fe─O coordination interaction of Fe with the OH in alkalized MXene nanosheets (L-Ti 3 C 2 -OH). As a result, FePc/L-OH/CN exhibits an impressive ORR activity with a half-wave potential (E 1/2 ) of 0.92 V, which is superior over the catalysts with a single junction and the state-of-the-art Pt/C (E 1/2 = 0.85 V). This work provides a broad idea for deep regulation of electronic state by the unidirectional cascade multi-step charge transfer and can be extended to other proton-coupled electron transfer processes.