Ni II ‐Porphyrin Metallo‐Supramolecular Gel Electrodes for Solar‐Driven Water Oxidation Coupled With Dark CO 2 Reduction

ABSTRACT Developing a single material capable of driving simultaneous photoelectrochemical (PEC) water oxidation and dark CO 2 reduction offers an appealing strategy for solar‐fuel production, yet remains largely unexplored in soft metallo‐supramolecular systems. Herein, a porphyrin‐based Ni(II)‐coordinated metallo‐supramolecular gel (Ni‐CPG) is developed as a dual‐functional catalyst for PEC applications. In the PEC cell, Ni‐CPG enables visible‐light‐driven water oxidation acting as a photoanode. To boost the water oxidation performance, a TiO 2 electron‐transporting layer (ETL) was integrated with Ni‐CPG, creating a type‐II heterojunction (TiO 2 /Ni‐CPG) that facilitates interfacial charge separation and transport. Kelvin probe force microscopy (KPFM) and Mott‐Schottky analysis confirm a facile electron transfer pathway from Ni‐CPG to TiO 2 . The resulting hybrid photoanode delivered a remarkable photocurrent density (∼121.96 µA.cm −2 at 1.23 V vs. RHE), representing a ∼203‐fold improvement over pristine Ni‐CPG, with charge transfer efficiency exceeding 63%. In a H‐type PEC cell, Ni‐CPG is employed as heterojunction photoanode and dark cathode simultaneously, achieving a Faradaic efficiency >94% for selective CO 2 ‐to‐CO conversion at 1.57 V versus RHE. Furthermore, in‐situ FTIR spectroscopy and DFT calculations unveiled the CO 2 reduction pathway and key intermediates. This study highlights the potential of metallo‐supramolecular polymer gel as a dual functional catalyst for water oxidation and dark CO 2 ‐to‐fuel production.