Light-assisted hydrogen evolution at a Pt cathode using [Ru(bpy)₃]-intercalated layered MnO₂ anodes

Embedding photoactive coordination complexes within redox-active layered oxides offers a route to couple molecular excited-state chemistry with inorganic electrode reactions. Here, [Ru(bpy)₃]²⁺-intercalated layered MnO₂ was electrodeposited on a conductive bamboo-charcoal/carbon-nanotube composite and used as an anode for H₂ evolution at a Pt cathode. At +1.10 V vs. Ag/AgCl in 0.5 M Na₂SO₄, three independent experiments yielded 0.87 ± 0.15 mL H₂ after 3 h under 300 nm irradiation, 4.4 times the dark value (0.20 ± 0.05 mL), with a faradaic efficiency of 80.3 ± 14.4%. Although incident and estimated absorbed photon flux densities at 450 and 600 nm exceeded those at 300 nm by more than 400-fold, the 300 nm condition produced the largest H₂ evolution and total charge, excluding a simple light-intensity or whole-electrode-absorption explanation. Post-electrolysis spectroscopy, ICP-MS, and semiquantitative redox-potential analysis support a model in which photoexcitation of interlayer [Ru(bpy)₃]²⁺ contributes to Mn(III)/Mn(IV)-related redox cycling, while the elementary electron-transfer and ionic charge-compensation pathways remain unresolved. These findings show that interlayer coordination-complex design can couple molecular photoexcitation with redox-active layered oxide electrodes for light-assisted hydrogen generation.