KuQuinone-Sensitized Cobalt Oxide Nanoparticles for Photoelectrocatalytic Oxygen Evolution with Visible Light

Photocatalytic nanomaterials offer promising solutions for conducting chemical transformations under safe, green and sustainable conditions. In particular, the storage of solar energy into chemical bonds is an appealing but challenging goal in the field of artificial photosynthesis. Using water as the source of electrons and protons through the photodriven water oxidation (WO) reaction is at the core of this endeavor. However, photocatalytic systems require carefully designed modular architectures to drive light-induced charge separation and oxygenic catalysis. In this work, we disclose photoactive hybrid nanomaterials designed through a dyadic approach. We exploit cobalt oxide nanoparticles covalently functionalized with a pentacyclic polyquinoid KuQuinone (KuQ) chromophore, providing a rare example of a photocatalytic dyadic nanomaterial (hereafter denoted as KuQ3Pn@Co3O4) based on the combination of a noble metal-free nanocatalyst a fully organic dye. The KuQ3Pn@Co3O4 nanomaterials are characterized combining high-resolution-TEM, STEM-HAADF imaging with XAS, XPS, resonance Raman, FT-IR and fluorescence spectroscopies. When casted onto a SnO2 photoanode, they are active towards photoelectrochemical WO upon visible light irradiation (400-580 nm) with an O2 Faradaic efficiency of ca. 90%. The combination of photophysical, photoelectrochemical and spectroscopic characterizations suggests communication via fast electron transfer between Co3O4 and KuQ dye, and identifies active Co oxo/hydroxo sites at the nanoparticle surface under operative conditions. Taken as a whole, this work brings a novel contribution to the rational design and mechanistic understanding of hybrid photocatalytic nanomaterials, retaining interest in energy and sustainable synthesis applications.