CrOx-mediated performance enhancement of Ni/NiO-Mg:SrTiO3in photocatalytic water splitting

Kai Han, Diane M. Haiber, Julius Knöppel, C. Lievens, Serhiy Cherevko, Peter Crozier, Guido Mul*, Bastian Mei*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

By photodeposition of CrOx on SrTiO3-based semiconductors doped with aliovalent Mg(II) and functionalized with Ni/NiOx catalytic nanoparticles (economically significantly more viable than commonly used Rh catalysts), an increase in apparent quantum yield (AQYs) from ∼10 to 26% in overall water splitting was obtained. More importantly, deposition of CrOx also significantly enhances the stability of Ni/NiO nanoparticles in the production of hydrogen, allowing sustained operation, even in intermittent cycles of illumination. In situ elemental analysis of the water constituents during or after photocatalysis by inductively coupled plasma mass spectrometry/optical emission spectrometry shows that after CrOx deposition, dissolution of Ni ions from Ni/NiOx-Mg:SrTiO3 is significantly suppressed, in agreement with the stabilizing effect observed, when both Mg dopant and CrOx are present. State-of-the-art electron microscopy and energy-dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS) analyses demonstrate that upon preparation, CrOx is photodeposited in the vicinity of several, but not all, Ni/NiOx particles. This implies the formation of a Ni-Cr mixed metal oxide, which is highly effective in water reduction. Inhomogeneities in the interfacial contact, evident from differences in contact angles between Ni/NiOx particles and the Mg:SrTiO3 semiconductor, likely affect the probability of reduction of Cr(VI) species during synthesis by photodeposition, explaining the observed inhomogeneity in the spatial CrOx distribution. Furthermore, by comparison with undoped SrTiO3, Mg-doping appears essential to provide such favorable interfacial contact and to establish the beneficial effect of CrOx. This study suggests that the performance of semiconductors can be significantly improved if inhomogeneities in interfacial contact between semiconductors and highly effective catalytic nanoparticles can be resolved by (surface) doping and improved synthesis protocols.

Original languageEnglish
Pages (from-to)11049-11058
Number of pages10
JournalACS catalysis
Volume11
Issue number17
Early online date20 Aug 2021
DOIs
Publication statusPublished - 3 Sep 2021

Keywords

  • co-catalyst
  • in situ ICP-MS
  • photocatalytic water splitting
  • SrTiO
  • stability
  • UT-Hybrid-D
  • ITC-ISI-JOURNAL-ARTICLE
  • ITC-HYBRID

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