Dyadic Ru-based nanomaterials for visible light-driven photocatalytic hydrogen evolution

Visible light-driven water splitting is an appealing strategy to store renewable energy in the chemical bonds of molecular hydrogen. In this regard, the development of photocatalytic architectures where charge transfer and recombination can be controlled represents a key challenge. The surface functionalization of Ru/RuO nanoparticles (NPs) with the [Ru(2,2'-bpy)(qpy)](PF) photosensitizer (PS), yielding PS-NPs "dyadic" hybrid nanomaterials, represents a promising strategy. Four HER photocatalysts with different PS:NPs ratios are synthesized and thoroughly characterized by analytical and spectroscopic techniques. X-ray photoelectron spectroscopy (XPS) reveals the covalent binding of the PS to the NPs surface. Analysis of the photocatalytic performance in aqueous triethanolamine (TEOA) shows that the activation of the nanocatalyst (RuO reduction) and the hydrogen evolution rate improves when the PS loading increases. Under visible-light irradiation, the nanomaterials with higher PS loading show sustained production of hydrogen for at least 80 h. The morphological and compositional evolution of the hybrid nanomaterials under photocatalytic conditions is studied and correlated with hydrogen production rates over time, pointing to a sequential leaching of PS from the nanomaterials surface. Additionally, photophysical experiments allow attaining an insight into the photochemical mechanism, which involves oxidative quenching with a fast electron injection, but also fast back electron transfer.