Milestone achieved in hybrid molecular materials for solar fuel generation

22nd April 2025 – A study led by Professor Antoni Llobet from ICIQ presents a supramolecular strategy that enables the stable and efficient use of molecular water oxidation catalysts on conductive oxide electrodes. This approach addresses a longstanding challenge in the field of solar fuel generation by combining the catalytic activity of molecular systems with the robustness of oxide-based materials.

Recently published in the Journal of the American Chemical Society, the research reports a method for integrating molecular catalysts into oxide electrodes without loss of performance.

“We designed these systems to combine the efficiency of molecular catalysts with the robustness of oxide surfaces, and now we have found a way to make them work together effectively,” said Prof. Llobet.

Supramolecular interface improves performance

The strategy involves a self-assembled bilayer composed of long alkyl chains attached to both the molecular catalyst and the functionalised oxide surface. This arrangement prevents direct contact between the two components, while still allowing electron transfer. It also includes an electron transfer mediator to accelerate charge transport between the electrode and the catalyst.

“Our approach creates highly stable assemblies that retain performance over long periods, even under neutral conditions,” said Paula Tris-Marzo, first author of the study.

The research focuses on a ruthenium-based oligomer (Ru-tb12) bearing 26 flexible alkyl chains. These chains interact with alkyl silanotrisolate-modified oxide electrodes through non-covalent interactions, resulting in a stable hybrid molecular anode. The system demonstrated consistent water oxidation activity at pH 7 for over 15 hours, with current densities of 0.40 mA/cm², turnover numbers exceeding 33,800, and Faradaic efficiencies above 92%.

Addressing Limitations in Solar Fuel Technologies

Compared to oxide-only systems, the hybrid anodes require significantly less mass to achieve comparable performance. The configuration avoids common issues such as catalyst dissolution, aggregation, and phase changes.

Water oxidation is a key reaction in the production of solar fuels through water splitting. While molecular water oxidation catalysts have shown high activity, their integration into oxide-based systems has posed difficulties due to stability and performance losses. This study provides a proof of concept that supramolecular assembly can offer a practical solution.

Reference publication

Molecular Anodes for Electrocatalytic Water Oxidation Based on Self-Assembled Bilayers Driven by Electron Transfer Mediators
Tris-Marzo, P.; Veclani, D.; Venturini, A.; Martínez-Belmonte, M.; Gil-Sepulcre, M.; Llobet, A
J. Am. Chem. Soc. 2025, 147 (15), 12686–12695
DOI: 10.1021/jacs.5c00489