Increased Water Reduction Efficiency of Polyelectrolyte-Bound Trimetallic [Ru,Rh,Ru] Photocatalysts in Air-Saturated Aqueous Solutions

The groundbreaking use of polyelectrolytes to increase the efficiency of supramolecular photocatalysts in solar H2 production schemes under aqueous aerobic conditions is reported. Supramolecular photocatalysts of the architecture [{(TL)2Ru(BL)}2RhX2]5+ (BL=bridging ligand, TL=terminal ligand, X=halide) demonstrate high efficiencies in deoxygenated organic solvents but do not function in air‐saturated aqueous solution because of the quenching of the metal‐to‐ligand charge‐transfer (MLCT) excited state under these conditions. The new photocatalytic system incorporates poly(4‐styrenesulfonate) (PSS) into aqueous solutions containing [{(bpy)2Ru(dpp)}2RhCl2]5+ (bpy=2,2′‐bipyridine, dpp=2,3‐bis(2‐pyridyl)pyrazine). PSS has a profound impact on the photocatalyst efficiency, increasing H2 production over three times that of deoxygenated aqueous solutions alone. H2 photocatalysis proceeds even under aerobic conditions for PSS‐containing solutions, an exciting consequence for solar hydrogen‐production research. Gemeinsam mehr erreichen: Ein unter aeroben Bedingungen arbeitendes Photokatalysesystem wurde entwickelt, dessen Photokatalyseeinheiten für die Wasserreduktion elektrostatisch an Poly(4‐Styrolsulfonat) (PSS) gebunden ist. Die wasserlöslichen Komplex‐PSS‐Aggregate bildeten sich in situ nach Zugabe von PSS zu den Photokatalysatorlösungen. PSS‐haltige wässrige Lösungen zeigen eine starke Wasserstoffentwicklung (siehe Bild).