Non-noble metal complexes are employed as co-catalysts of m-TiO₂ to improve the photocatalytic production of green hydrogen from water photolysis. Six new copper(I) pyridinium–selenolate complexes have been fully characterized and utilized for the development of photocatalysts intended for heterogeneous photocatalysis.

The reaction of 1,2-bis(3-aminopyridin-2-yl)diselane (apySe)₂ with [CuX(PPh₃)₃] (X = Cl, Br, I) yields monomers and the dimers coordination compounds. In both cases, the reduction of the diselane is observed, leading to the formation of 3-aminopyridinium-2-selenolate ligand. The complexes are characterized using spectroscopic and electrochemical methods, as well as single-crystal X-ray diffraction analysis. They are used as co-catalysts of mesoporous titania, for the preparation of photocatalysts. All photocatalysts synthesized are active for the hydrogen production by water photolysis. The m-TiO₂-1 and m-TiO₂-4 photocatalysts stood out, producing 2505 and 2423 μmol g⁻¹ of hydrogen, respectively, after 6 h of irradiation with a 300 W Hg/Xe lamp. Their activities greatly exceed the amount observed for pure m-TiO₂, being approximately eight times higher. Through recycling experiments, the stability of the most efficient m-TiO₂-1 photocatalyst is verified, demonstrating the suitable impregnation of the co-catalyst over the m-TiO₂ matrix and the importance of the complex to improve the ability of the photocatalyst to increase the absorption of visible radiation. These results highlight the potential of pyridinium–selenolate copper(I) complexes, to act as effective co-catalysts of m-TiO₂, for hydrogen production via water photolysis, making them promising candidates for applications in heterogeneous photocatalysis processes.