Bismuth oxyhalide films as photoelectrodes

Open paper intelligence

AACVD BiOX films show halide-tuned bandgaps; untreated BiOBr gives about 0.38 mA cm−2 photoanodic current without a sacrificial donor.

Source

Bismuth oxyhalides: synthesis, structure and photoelectrochemical activity

Bhachu DS, Moniz SJA, Sathasivam S, et al. · Chemical science · 2016

doi.org/10.1039/c6sc00389c Read the full paper ↗90 citationscc by

Study at a glance

Design: Other — AACVD BiOX film deposition with band-structure analysis and photoelectrochemical testing
N: Materials photoelectrochemistry — no sample N
Population: BiOCl, BiOBr, and BiOI thin-film photoelectrodes
Outcome: Photoelectrochemical activity and band-edge positions of BiOX films

Structured fields used in claim comparison tables when every cited study has a complete layer.

What they did

Authors deposited BiOCl, BiOBr and BiOI at 300 °C by AACVD, measured XRD/SEM/UV-vis/XPS, computed band structures, and ran PEC in 0.5 M Na2SO4 under 100 mW cm−2 with Mott–Schottky analysis.

What they found

Phase-pure tetragonal matlockite films. Nanoplatelets for Cl/I, nanoflowers for Br. Bandgap narrowing follows halide p orbital energy in the valence band. Untreated BiOCl (p-type) and BiOI (n-type) are unstable for PEC; BiOBr gives ca. 0.38 mA cm−2 at 1 V vs Ag/AgCl, the highest BiOBr photocurrent without a sacrificial donor.

The limits

What it doesn't show

Long-term tandem-cell solar-to-hydrogen efficiency is not reported; untreated Cl and I films fail stability, so they are not practical photoelectrodes as-made.

Key terms

AACVD: Aerosol-assisted chemical vapour deposition used to grow the BiOX films.
Matlockite: Tetragonal layered BiOX structure type.
Mott–Schottky: Capacitance–voltage plot that reports n- vs p-type character and flat-band potential.
Photoanode: n-type semiconductor electrode that oxidizes water (or electrolyte) under light.
Halide p valence band: Cl/Br/I p orbitals that raise the VBM and shrink the gap from Cl to I.

Flashcards

1 / 11

Research intelligence for this paper

See its role on concept claims, tensions it is part of, placement history, and related discoveries.

Open paper intelligence

Quiz yourself

1 / 6

Usable untreated photoanode in this series:

Common questions

Which film is the usable photoanode?

BiOBr, ~0.38 mA cm−2 at 1 V vs Ag/AgCl.

Why do gaps shrink Cl→I?

Halide p orbitals that form the upper valence band rise in energy.

BiOCl type?

p-type; possible photocathode on paper, but poor PEC stability.

Deposition temperature?

300 °C for 60 min.