Semiempirical modeling of a three sublayer photoanode for highly efficient photoelectrochemical water splitting : Parameter and electrolyte optimizations

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

2 Scopus Citations
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Author(s)

  • Mimoza M. Ristova
  • Wei Zhu
  • Kin Man Yu
  • Wladyslaw Walukiewicz

Detail(s)

Original languageEnglish
Pages (from-to)190-199
Journal / PublicationSolar Energy Materials and Solar Cells
Volume157
Publication statusPublished - 1 Dec 2016

Abstract

Below we present semiempirical modeling of conceptually new three-sublayer photoanode, composed of Absorber, Grading and Barrier sublayers, for highly efficient photoelectrochemical water dissociation. The modeling resulted into Absorber (Sub-A) made of Cd0.55Zn0.45O due to its favorable positions of the band extrema to the water splitting potentials and a band gap ~2.0 eV. The Grading layer (Sub-G) was composed of CdxZn1-xO with a gradual decrease of x across the profile, changing from 0.2 to 0.55, aiming to photon absorption from 2.0 to 3.0 eV. At the same time, Sub-G furnishes the profile with an implanted electrical field that improves the hole-transport. The electron Barrier layer (Sub-B) deposited above the Sub-A, was engineered to provide 1 eV high barrier in the conduction band. It comprised of a 50 nm thick Ni0.4Cd0.6O film with Eg~3.0 eV with a valence band aligned to the one of the Sub-A, providing a barrier-free hole-flow. In this paper, we provide evidence that the proposed three-sublayer concept clearly represents a new paradigm for an improved efficiency for photocatalytic water dissociation. The highest photocatalytic activity of the optimized profile was achieved with an optimized electrolyte: 87% 1 M K2HPO4 and 13% 1 M Na2SO3 (known to act as a hole scavenger or sacrificial agent) at pH=10. A noteworthy feature of this study is that under optimized profile parameters and customized electrolyte conditions the photocurrent yields increased from ~0.05 mA/cm2 to ~20 mA/cm2 at +1.2 V for visible light. The observed Incident Photon-to-Current Efficiency (IPCE) was about 50% measured at a photon energy of 3 eV.

Research Area(s)

  • CdZnO/NiCdO, IPCE, Photoanodes, Photosensitivity, Voltammetry, Water splitting

Citation Format(s)

Semiempirical modeling of a three sublayer photoanode for highly efficient photoelectrochemical water splitting : Parameter and electrolyte optimizations. / Ristova, Mimoza M.; Zhu, Wei; Yu, Kin Man; Walukiewicz, Wladyslaw.

In: Solar Energy Materials and Solar Cells, Vol. 157, 01.12.2016, p. 190-199.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review