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Transient Behavior of Ni@NiO x Functionalized SrTiO 3 in Overall Water Splitting

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ABSTRACT

Transients in thecomposition of Ni@NiOx core–shellco-catalysts deposited on SrTiO3 arediscussed on the basis of state-of-the-art continuous analysis ofphotocatalytic water splitting, and post-XPS and TEM analyses. Theformation of excessive hydrogen (H2:O2 ≫2) in the initial stages of illumination demonstrates oxidation ofNi(OH)2 to NiOOH (nickel oxyhydroxide), with the lattercatalyzing water oxidation. A disproportionation reaction of Ni andNiOOH, yielding Ni(OH)2 with residual embedded Ni, occurswhen illumination is discontinued, which explains repetitive transientsin (excess) hydrogen and oxygen formation when illumination is reinitiated.

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XPS spectra of the Ni 2p3/2 regionof the BSTO1000-NiOx sample: (i) beforeillumination Ni@NiOx/STO (as prep.), (ii)after illuminationNi@NiOx/STO (meas.), and (iii) after regeneration(48 h) Ni@NiOx/STO (reg.).
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fig3: XPS spectra of the Ni 2p3/2 regionof the BSTO1000-NiOx sample: (i) beforeillumination Ni@NiOx/STO (as prep.), (ii)after illuminationNi@NiOx/STO (meas.), and (iii) after regeneration(48 h) Ni@NiOx/STO (reg.).

Mentions: The Ni@NiOx co-catalyst was characterizedafter different treatments in order to explain the observed transients.The X-ray photoelectron spectra in the Ni region of the BSTO1000-NiOx catalyst before illumination, after illumination,and after 48 h of treatment in darkness, are compared in Figure 3. For the as-prepared BSTO1000-NiOx composite, a complex Ni peak shape is observed, evidencingthat Ni is present in various oxidation states. Deconvolution of theNi 2p3/2 signal confirms the presence of metallic Ni0 (at 851.9 eV), Ni2+ (as in NiO at 853.5 eV), andNi2+ (as in Ni(OH)2 at 855.6 eV).10−12 The derived relative percentages of Ni metal and Ni oxide, as wellas the overall atomic Ni content, are shown in Table 1.


Transient Behavior of Ni@NiO x Functionalized SrTiO 3 in Overall Water Splitting
XPS spectra of the Ni 2p3/2 regionof the BSTO1000-NiOx sample: (i) beforeillumination Ni@NiOx/STO (as prep.), (ii)after illuminationNi@NiOx/STO (meas.), and (iii) after regeneration(48 h) Ni@NiOx/STO (reg.).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5384480&req=5

fig3: XPS spectra of the Ni 2p3/2 regionof the BSTO1000-NiOx sample: (i) beforeillumination Ni@NiOx/STO (as prep.), (ii)after illuminationNi@NiOx/STO (meas.), and (iii) after regeneration(48 h) Ni@NiOx/STO (reg.).
Mentions: The Ni@NiOx co-catalyst was characterizedafter different treatments in order to explain the observed transients.The X-ray photoelectron spectra in the Ni region of the BSTO1000-NiOx catalyst before illumination, after illumination,and after 48 h of treatment in darkness, are compared in Figure 3. For the as-prepared BSTO1000-NiOx composite, a complex Ni peak shape is observed, evidencingthat Ni is present in various oxidation states. Deconvolution of theNi 2p3/2 signal confirms the presence of metallic Ni0 (at 851.9 eV), Ni2+ (as in NiO at 853.5 eV), andNi2+ (as in Ni(OH)2 at 855.6 eV).10−12 The derived relative percentages of Ni metal and Ni oxide, as wellas the overall atomic Ni content, are shown in Table 1.

View Article: PubMed Central - PubMed

ABSTRACT

Transients in thecomposition of Ni@NiOx core–shellco-catalysts deposited on SrTiO3 arediscussed on the basis of state-of-the-art continuous analysis ofphotocatalytic water splitting, and post-XPS and TEM analyses. Theformation of excessive hydrogen (H2:O2 ≫2) in the initial stages of illumination demonstrates oxidation ofNi(OH)2 to NiOOH (nickel oxyhydroxide), with the lattercatalyzing water oxidation. A disproportionation reaction of Ni andNiOOH, yielding Ni(OH)2 with residual embedded Ni, occurswhen illumination is discontinued, which explains repetitive transientsin (excess) hydrogen and oxygen formation when illumination is reinitiated.

No MeSH data available.


Related in: MedlinePlus