Hydrogen evolution and iodine reduction on an illuminated n-p junction silicon electrode and its application to efficient solar photoelectrolysis of hydrogen iodide
A p-type silicon electrode, highly doped with phosphorus from the surface (hereafter abbreviated as an n/sup +//p-Si electrode), generated a photocurrent corresponding to iodine (or triiodide) reduction in a hydrogen iodide/iodine solution at potentials much more positive than those at platinum and p-Si electrodes. The photocurrent-potential curve did not change when the electrode was illuminated for 60 h at a sufficiently cathodic potential, but changed due to the formation of a thin silicon oxide layer at the surface when illuminated near the onset potential of the photocurrent. The kinetics of the photoevolution of hydrogen on the n/sup +//p-Si electrode in acid solutions were improved by depositing a 0.5-3 nm thick platinum layer on the surface. The hydrogen-evolution photocurrent at the Pt-coated n/sup +//p-Si electrode gradually decayed under prolonged illumination, but was restored to the initial value by keeping the electrode in an oxidative condition. This suggests that the decay is due to the formation of a reduced surface species. Photoelectrochemical cells constructed with a Pt-deposited n/sup +//p-Si electrode and a Pt counterelectrode separated by a commercial cation-exchange membrane electrolyzed hydrogen iodide into hydrogen and triiodide ions under no externally applied voltage with an encouragingly high solar-to-chemical energy conversion efficiency (phi/sub chem//sup s/) of 7.8% under simulated solar AM 1 radiation. 30 references, 8 figures.
- Research Organization:
- Osaka Univ., Toyonaka, Japan
- OSTI ID:
- 6167697
- Journal Information:
- J. Phys. Chem.; (United States), Vol. 88:19
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
HYDRIODIC ACID
PHOTOELECTROLYSIS
HYDROGEN PRODUCTION
IODINE
REDUCTION
CHEMICAL REACTION KINETICS
CRYSTAL DOPING
CURRENT DENSITY
ELECTRODEPOSITED COATINGS
ELECTRODES
EXPERIMENTAL DATA
PHOSPHORUS
PHOTOCATHODES
PHOTOELECTROCHEMICAL CELLS
PLATINUM
SILICON
TIME DEPENDENCE
CATHODES
CHEMICAL REACTIONS
COATINGS
DATA
ELECTROCHEMICAL CELLS
ELECTROLYSIS
ELEMENTS
EQUIPMENT
HALOGEN COMPOUNDS
HALOGENS
HYDROGEN COMPOUNDS
INFORMATION
INORGANIC ACIDS
IODINE COMPOUNDS
KINETICS
LYSIS
METALS
NONMETALS
NUMERICAL DATA
PLATINUM METALS
REACTION KINETICS
SEMIMETALS
SOLAR EQUIPMENT
TRANSITION ELEMENTS
080106* - Hydrogen- Production- Biosynthesis & Photochemical Processes