Factors influencing the photoelectrochemical device performance sensitized by ruthenium polypyridyl dyes

• Published in: Dalton transactions : an international journal of inorganic chemistry 2019-01, Vol.48 (2), p.688-695
• Main Authors: Purnama, Indra, Salmahaminati, Abe, Minori, Hada, Masahiko, Kubo, Yuji, Mulyana, Jacob Yan
• Format: Article
• Language: English
• Subjects: Chains; Conduction bands; Dyes; Electrochemistry; Electrolytic cells; Ethylenediaminetetraacetic acids; Hole mobility; Hydrogen production; Mathematical analysis; Phosphorescence; Photoelectric effect; Photoelectric emission; Photoelectrochemical devices; Photoelectrochemistry; Ruthenium compounds; Titanium dioxide
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c8dt03502d

The dye-sensitized photoelectrochemical cells (DSPECs) incorporating a family of ruthenium complexes [Ru II (bipyP)(bipy) 2 ] ( P1 ), [Ru II (bipyP)(dmb) 2 ] ( P2 ), [Ru II (bipyP)(dtbb) 2 ] ( P3 ) and [Ru II (bipyP)(dnb) 2 ] ( P4 ), where bipyP = 2,2′-bipyridine-4,4′-diphosphonic acid, bipy = 2,2′-bipyridine, dmb = 4,4′-dimethyl-2,2′-bipyridine, dtbb = 4,4′-di- tert -butyl-2,2′-bipyridine, and dnb = 4,4′-dinonyl-2,2′-bipyridine, were fabricated in a dye-only system ( do -DSPEC) and in a system where the electrolyte solution was loaded with EDTA sacrificial agent ( sa -DSPEC). The increasing number of the alkyl chains of the ancillary bipy ligand shifts the ground- and excited-state potentials to the more negative values, although the introduction of the longer nonyl chain in P4 shows the opposite effect. In do -DSPECs, the photocurrent and hydrogen production performance follows the order P4 > P3 > P2 > P1 , which correlates well with the degree of the excited-state quenching by electron injection to the conduction band of TiO 2 . The photoelectrochemistry of the sa -DSPECs reveals 10 times as many photocurrents as that measured in do -DSPECs, suggesting the ability of the hole to oxidize EDTA molecule. The hydrogen production performance of sa -DSPECs over five hours follows the order P2 > P1 > P3 > P4 , which is consistent with the Ru III /Ru II reorganization energies and the hole mobility on the TiO 2 surface. The present study provides evidence that the subtle alkyl chain variation of the ruthenium photosensitizers can fine tune the electron injection capacity, Ru III /Ru II self-exchange energetics and photostability of the complexes, which significantly influence the performance of the DSPECs. The subtle variation in the alkyl substituents of the ruthenium photosensitizers controls the photo-electrochemical performance of the dye-only DSPECs ( do -DSPECs) and those with sacrificial agent ( sa -DSPECs).