Polymer Networks Assembled by Ruthenium Catalysts for Enhanced Water Splitting Performance in Calixarene Dye-Sensitized Photoelectrochemical Cells

Metal-free photosensitizers for the construction of low-cost and eco-friendly dye-sensitized photoelectrochemical cells (DSPECs) have recently been greatly improved, but the optimization of water oxidation catalysts (WOCs) used in DSPECs based on metal-free dyes has received little attention. Herein, a series of polymer networks (RuTPA, RuCz, RuPr and RuTz) assembled by ruthenium WOCs (RuCHO) with various organic donors are constructed and combined with calixarene dyes to prepare DSPEC devices. The FTO|TiO2|C4BTP+RuTPA photoanode shows the best performance with 85 % Faraday efficiency for oxygen production and 477 μA cm-2 photocurrent density after 200 s chopping irradiation at 0 V vs. Ag/AgCl, one of the highest records among other reported dye-sensitized photoanodes. Compared to monomeric RuCHO, Ru-based polymers with lower Ru content have higher activity and stability due to their rapid electron transfer and anti-aggregation ability. Meanwhile, RuTPA loaded electrodes show better performance due to the lower overpotential of the water oxidation reaction caused by the higher electron donating ability of its donor. This pioneering work incorporates Ru polymer networks as WOCs into the calixarene-sensitized DSPEC system, which has significant potential as a highly efficient and stable photoelectrochemical water splitting device.

Water Oxidation Molecular Assemblies in Dye-Sensitized Photoelectrochemical Cell: An Overview

Dye-sensitized photoelectrochemical cells (DSPECs) are efficient and sustainable approaches for hydrogen production via water splitting, driven by solar energy. Recent advancements have focused on enhancing the performance and stability of photoanodes, which are critical for efficient water oxidation. Herein discussed are the latest innovations including the development of metal-free organic sensitizers, improved chromophore-catalyst assemblies, and core-shell structures. These advances lead to reduced electron-hole recombination, increased light absorption, and enhanced electron transfer efficiency. Pyridine-anchored sensitizers have shown superior stability compared to traditional carboxylate and phosphate anchors in water, while covalently linked chromophores and molecular catalysts provide long-term operational stability. Together, these improvements bring DSPEC technology closer to practical applications in green hydrogen production, addressing key challenges of energy efficiency, scalability, and system durability. These approaches could be explored further toward realizing cost-effective hydrogen production.

KuQuinones: a ten years tale of the new pentacyclic quinoid compound

Quinones are widespread in nature, as they participate, mainly as redox mediators, in several biochemical processes. Up to now, various synthetic quinones have been recommended in the literature as leading molecules in energy, biomedical and catalytic fields. In this brief review, we retraced our research activity in the last ten years, mainly dedicated to the study of a new class of peculiar pentacyclic conjugated quinoid compounds, synthesized in our group. In particular, their application as sensitive materials in photoelectrochemical devices and in biosensors, as photocatalysts in selective oxidation reactions, and their anticancer activity is here reviewed.

Dye-catalyst dyads for photoelectrochemical water oxidation based on metal-free sensitizers

Dye-Sensitized Photoelectrochemical Cells (DS-PECs) have been emerging as promising devices for efficient solar-induced water splitting. In DS-PECs, dyes and catalysts for water oxidation and/or reduction are typically two separate components, thus limiting charge transfer efficiency. A small number of organometallic dyes have been integrated with a catalyst to form an integrated dye–catalyst dyad for photoanodes, but until now no dyads based on metal-free organic dyes have been reported for photoanodes. We herein report the first example of dyad-sensitized photoanodes in DS-PEC water splitting based on metal-free organic dyes and a Ru catalyst. The di-branched donor–π–acceptor dyes carry a donor carbazole moiety which has been functionalized with two different terminal pyridyl ligands in order to coordinate a benchmark Ru complex as a water oxidation catalyst, affording water oxidation dyads. The two dyads have been fully characterized in their optical and electrochemical properties, and XPS has been used to confirm the presence of the catalyst bonded to the dye anchored to the semiconductor anode. The two dyads have been investigated in DS-PEC, showing an excellent faradaic efficiency (88% average across all cells, with a best cell efficiency of 95%), thus triggering new perspectives for the design of efficient molecular dyads based on metal-free dyes for DS-PEC water splitting.

Dye–catalyst dyads based on metal-free dyes were prepared for dye-sensitized photoanodes in photoelectrochemical water splitting, showing a top ranked faradaic efficiency for O₂ generation up to 95%.

Wavelength dependence and wavelength selectivity in photochemical reactions

Our study describes how organic photochemists can modify the outcome of a reaction by tuning the wavelength.