Fig. 4

Illustration of IR-light-to-energy conversion and photoelectrochemical measurements. a The photoelectrochemical cell configuration and schematic illustration of IR-light-to-energy conversion using the plasmonic ITO/SnO₂ heterointerface (the reference electrode is omitted for clarity). b Action spectra of ITO-NC/SnO₂/W photoelectrodes. The filled and empty blue circles correspond to the ICPE of the ITO-NC/SnO₂/W electrode and the SnO₂/W electrode, respectively. The blue solid line is the diffuse-reflectance spectrum of the ITO-NC/SnO₂/W electrode. IPCE measurements under irradiation by light of wavelengths longer than 1600 nm was not carried out due to the limitations of our instrument. Experiments were performed in an acetonitrile solution of triethanolamine (10% v/v) containing 0.1-M tetrabutylammonium hexafluorophosphate. c, d Photoelectrochemical measurement of an ITO NCs/SnO₂/W electrode under SWIR irradiation. Short-circuit photocurrent and time (I-t) curves under irradiation by a chopped Xe lamp through a broadband pass filter (1615 nm–2280 nm, 104 mW cm⁻² or 2093 nm–2547 nm, 33 mW cm⁻²) using a three-electrode setup (blue line). (Working electrode: ITO NCs/SnO₂/W electrode; Reference electrode: Ag⁺/Ag; Counter electrode: Pt wire; Photoactive area: 2.5 × 1.5 cm²; Solution: acetonitrile solution of triethanolamine (10% v/v) containing 0.1-M tetrabutylammonium hexafluorophosphate). The black line is an I-t curve obtained using the SnO₂/W electrode as a working electrode