Size-selected TiO2 nanocluster catalysts for efficient photoelectrochemical water splitting

Saurabh Srivastava, Joseph Palathinkal Thomas, Md Anisur Rahman, Marwa Abd-Ellah, Mamata Mohapatra, Debabrata Pradhan, Nina F. Heinig, Kam Tong Leung

Research output: Contribution to journalArticlepeer-review

63 Scopus citations

Abstract

Nanoclusters (NCs) are of great interest because they provide the link between the distinct behavior of atoms and nanoparticles and that of bulk materials. Here, we report precisely controlled deposition of size-selected TiO2 NCs produced by gas-phase aggregation in a special magnetron sputtering system. Carefully optimized aggregation length and Ar gas flow are used to control the size distribution, while a quadrupole mass filter provides precise in situ size selection (from 2 to 15 nm). Transmission electron microscopy studies reveal that NCs larger than a critical size (∼8 nm) have a crystalline core with an amorphous shell, while those smaller than the critical size are all amorphous. The TiO2 NCs so produced exhibit remarkable photoelectrochemical water splitting performance in spite of a small amount of material loading. NCs of three different sizes (4, 6, and 8 nm) deposited on H-terminated Si(100) substrates are tested for the photoelectrochemical catalytic performance, and significant enhancement in photocurrent density (0.8 mA/cm2) with decreasing NC size is observed with a low saturation voltage of -0.22 V vs Ag/AgCl (0.78 V vs RHE). The enhanced photoconductivity could be attributed to the increase in the specific surface area and increase in the number of active (defect) sites in the amorphous NCs. The unique advantages of the present technique will be further exploited to develop applications based on tunable, size-selected NCs. (Graph Presented).

Original languageBritish English
Pages (from-to)11891-11898
Number of pages8
JournalACS Nano
Volume8
Issue number11
DOIs
StatePublished - 25 Nov 2014

Keywords

  • Magnetron sputtering
  • Photoelectrochemical catalysts
  • Size selection
  • TiO nanoclusters
  • Water splitting reaction

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