Proton-Coupled Electron
Transfer on Mixed-Valent Copper
Ions Containing S- and N‑Rich Triazine-Dimercapto Thiadiazole
Coordination Polymer Photocathodes
posted on 2023-11-28, 14:35authored byPrashanth Vishwa, Sakthivel Kandaiah
Visible light-active semiconductor photoelectrocatalytic
interfaces
that are stable in protic electrolytes are essential for photoassisted
multiproton-coupled electron transfer in electro-synthetic processes.
Herein, we report a photocathode material with nitrogen- and sulfur-rich
functional ligands and a mixed-valent copper coordination polymeric
structure. A simple strategy of nucleophilic substitution reaction
between triazine trichloride and 2,5-dimercapto-1,3,5-thiadiazole
followed by coordination with mixed-valent copper ions is used to
prepare the metallopolymer. Spectral analysis evidences the systematic
bathochromic shift toward the midvisible region with the increase
in the extent of polymerization and increasing coordination of mixed-valent
copper ions. This p-type photoactive metallopolymer exhibits an optical
band gap of ∼2 eV with a repeatable photocurrent response of
80 to 100 μA cm–2 in strong protic media.
This is significantly high in correlation to metal-free polydimercapto
thiadiazole, polycopper dimercapto thiadiazole, and Cu2O. The incorporation of triazine units and CuII/I in the
thiadiazole polymeric network enables enhanced photoelectrochemical
activity and stability. In comparison to neutral electrolytes, the
photocurrent values observed are nearly 3 to 4 times higher in protic
electrolytes. The metallopolymer exhibits a nearly 30 to 40% increase
in photoinduced oxygen reduction current and good stability in protic
electrolytes.