title: All-in-One Derivatized Tandem p+n-Silicon-SnO2/TiO2Water Splitting Photoelectrochemical Cell.
abstract: Mesoporous metal oxide film electrodes consisting of derivatized 5.5 μm thick SnO2films with an outer 4.3 nm shell of TiO2added by atomic layer deposition (ALD) have been investigated to explore unbiased water splitting on p, n, and p+n type silicon substrates. Modified electrodes were derivatized by addition of the water oxidation catalyst, [Ru(bda)(4-O(CH2)3PO3H2)-pyr)2], 1, (pyr = pyridine; bda = 2,2'-bipyridine-6,6'-dicarboxylate), and chromophore, [Ru(4,4'-PO3H2-bpy) (bpy)2]2+, RuP2+, (bpy = 2,2'-bipyridine), which form 2:1 RuP2+/1 assemblies on the surface. At pH 5.7 in 0.1 M acetate buffer, these electrodes with a fluorine-doped tin oxide (FTO) back contact under ∼1 sun illumination (100 mW/cm2; white light source) perform efficient water oxidation with a photocurrent of 1.5 mA/cm2with an 88% Faradaic efficiency (FE) for O2production at an applied bias of 600 mV versus RHE ( ACS Energy Lett. , 2016 , 1 , 231 - 236 ). The SnO2/TiO2-chromophore-catalyst assembly was integrated with the Si electrodes by a thin layer of titanium followed by an amorphous TiO2(Ti/a-TiO2) coating as an interconnect. In the integrated electrode, p+n-Si-Ti/a-TiO2-SnO2/TiO2|-2RuP2+/1, the p+n-Si junction provided about 350 mV in added potential to the half cell. In photolysis experiments at pH 5.7 in 0.1 M acetate buffer, bias-free photocurrents approaching 100 μA/cm2were obtained for water splitting, 2H2O → 2H2+ O2. The FE for water oxidation was 79% with a hydrogen efficiency of ∼100% at the Pt cathode.
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Matthew V
authors.initials: MV
authors.lastname: Sheridan
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: David J
authors.initials: DJ
authors.lastname: Hill
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Benjamin D
authors.identifier: 0000-0001-9571-5065
authors.initials: BD
authors.lastname: Sherman
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Degao
authors.initials: D
authors.lastname: Wang
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Seth L
authors.initials: SL
authors.lastname: Marquard
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Kyung-Ryang
authors.initials: KR
authors.lastname: Wee
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: James F
authors.initials: JF
authors.lastname: Cahoon
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
authors.forename: Thomas J
authors.identifier: 0000-0002-7006-2608
authors.initials: TJ
authors.lastname: Meyer
keywords: Water splitting; core−shell; photoelectrochemistry; ruthenium; silicon; titanium dioxide