La₅Ti₂Cu_0.9Ag_0.1S₅O₇ Modified with a Molecular Ni Catalyst for Photoelectrochemical H₂ Generation

Abstract

The stable and efficient integration of molecular catalysts into p-type semiconductor materials is a contemporary challenge in photoelectrochemical fuel synthesis. Here, we report the combination of a phosphonated molecular Ni catalyst with a TiO -coated La Ti Cu Ag S O photocathode for visible light driven H production. This hybrid assembly provides a positive onset potential, large photocurrents, and high Faradaic yield for more than three hours. A decisive feature of the hybrid electrode is the TiO interlayer, which stabilizes the oxysulfide semiconductor and allows for robust attachment of the phosphonated molecular catalyst. This demonstration of an oxysulfide-molecular catalyst photocathode provides a novel platform for integrating molecular catalysts into photocathodes and the large photovoltage of the presented system makes it ideal for pairing with photoanodes.

Hybrid Photoelectrochemical Water Splitting Systems: From Interface Design to System Assembly

“…Very recently, Domen and co‐workers constructed a Ni catalyst ( 8, Figure 2) on the surface of TiO 2 ‐coated La 5 Ti 2 Cu 0.9 Ag 0.1 S 5 O 7 . When the nickel catalyst was anchored on a La 5 Ti 2 Cu 0.9 Ag 0.1 S 5 O 7 /TiO 2 electrode, an onset potential of +0.65 V versus RHE was obtained with a photocurrent of 0.6 mA cm −2 at 0 V versus RHE 52…”

“…In addition, the semiconductor electrode should possess long‐term stability under light irradiation conditions for water splitting reactions. To date, numerous semiconductor photoelectrodes have been developed for PEC water splitting, including p‐Si,25–35 p‐GaP,36–40 InP,41,42 Cu 2 O,43,44 CdSe quantum dots (QDs),45–49 CdS QDs50, p‐GaInP51, and La 5 Ti 2 Cu 0.9 Ag 0.1 S 5 O 7 52 for water reduction and α‐Fe 2 O 3 ,53–66 WO 3 ,67–75 BiVO 4 75–84 and n‐Si85 for water oxidation. For more information about the properties of the semiconductors, including the conduction (CB) and valence band (VB), stabilities as a function of pH values, the light absorption behavior, and advanced preparation methods for different morphologies, readers are invited to refer to related review papers 86–89…”

Photoelectrochemical Cells for Artificial Photosynthesis: Alternatives to Water Oxidation

“…This groundbreaking design offered the possibilities of varying the semiconductor electrodes, the photosensitizers, and the co‐catalysts used. This report has been followed by a number of recent variations where molecular co‐catalysts for H 2 evolution and CO 2 reduction were attached on the photocathodes instead of the photoanodes.…”

Hybrid photocathode based on a Ni molecular catalyst and Sb2Se3 for solar H2 production

“…22 Full details of the synthetic procedures, the device characterisation and SEM images are provided in the supporting information, Figs S2.1-3. The molecular catalyst was first immobilized overnight onto the sputtered TiO 2 (without the TiO 2 -meso) by soaking the photoelectrode in dry methanolic solution (0.5 mM NiP), 19,23,24 and from now on labelled as Sb 2 Se 3 /CdS/TiO 2 /NiP. It was removed from the soaking solution, thoroughly washed in methanol to remove the non-chemisorbed catalyst and dried under vacuum.…”

“…All the photoelectrochemical tests were done under 100 mW cm 2 illumination (unless otherwise stated) and with  > 340 nm in 0.1 M Na 2 SO 4 at pH 3. pH 3 was chosen due to past studies that showed NiP was most active at this pH. 23,25 Figure 2 shows a photocurrent of only 16 A cm 2 at 0 V vs RHE, which exceeds only slightly the current in the absence of any catalyst (3 A cm 2 for Sb 2 Se 3 /CdS/TiO 2 , Fig S2 .4). The spikes in the light chopped Linear Sweep Voltammetry (LSV) of Sb 2 Se 3 /CdS/TiO 2 /NiP demonstrated that the photoelectrons are not being utilised at a fast-enough rate by the catalyst, instead recombination is dominating.…”