On the Limits of Photocatalytic Water Splitting

The major drawbacks on the limited H2 and O2 evolution activities of one-step photocatalytic water splitting systems are given here with the emphasis on charge recombination, back-oxidation reactions, and mass transfer limitations. Suppression of these unwanted phenomena is shown to be possible with the usage of small crystal-sized photocatalysts with low defect concentrations, presence of phase junctions, selection of co-catalyst that would be active for H2 evolution but inactive for O2 reduction, coating of the co-catalyst or the whole photocatalyst with selectively permeable nanolayers, and usage of photocatalytic systems with high solid–liquid and liquid–gas surface areas. The mass transfer limitations are shown to be important especially in the liquid–gas interfaces for agitated and suspended systems with estimated H2 transfer rates in the range of ∼200–8000 μmol/h.


Development of Hydrogen Separation Membrane in Palladium Based Ternary Systems
Köse, Mehmet Mert; Öztürk, Tayfur; Department of Metallurgical and Materials Engineering (2022-1-25)
A study was carried out into dense metallic membranes for hydrogen separation. Two palladium-based system were characterized Pd-Mn-Ag and Pd-Co-Ni. Membranes were produced via sputter deposition in combinatorial geometry. For this purpose, sputter targets were arranged in triangular manner, and there were total of 21 substrates just above the targets. Membranes were screened via resistivity measurements under argon and hydrogen carried out up to 450 oC. A reactivity index defined as resistivity under hydrog...
The biocatalytic effect of Halobacterium halobium on photoelectrochemical hydrogen production
Sediroglu, V; Eroglu, I; Yucel, M; Turker, L; Gündüz, Ufuk (1999-04-30)
Hydrogen gas can be produced electrochemically by leading a current through two electrodes immersed in a NaCl solution. Bacteriorhodopsin (BR) a protein found in the purple membrane of Halobacterium halobium, is known to pump protons across the membrane upon illumination. In this study, the effect of BR on photoelectrochemical hydrogen production was investigated. A batch type bio-photoelectrochemical reactor was designed and constructed. The photoelectrochemical hydrogen production experiments were perform...
On the Electrochemical Reduction Mechanism of CaWO4 to W Powder
Erdogan, Metehan; Karakaya, İshak (2012-08-01)
The reduction mechanism of CaWO4 to W in molten eutectic CaCl2-NaCl electrolyte has been studied. Cyclic voltammetry and constant potential electrolysis tests were performed to determine the reversible cell potential. Analyses of the experimental results revealed that at least 2.2 V was required to compensate the potentials for the accompanying cell reaction and the electrode polarizations. A cell reaction was proposed by associating the experimental results and the Gibbs energy changes of the possible reac...
Development of activated carbon/bimetallic transition metal phosphide composite materials for electrochemical capacitors and oxygen evolution reaction catalysis
Köse, Kadir Özgün; Aydınol, Mehmet Kadri (2022-09-01)
Pinecone-derived activated carbon (AC) and bimetallic transition metal phosphide (TMP) composites were produced and utilized as electrochemical capacitor (EC) electrodes and oxygen evolution reaction (OER) catalysts in this study. The base transition metal (TM) was Ni for all samples, and the secondary TM was one of Fe, Mn and Co. AC serves as a porous structure for double layer formation and active sites for OER catalysis. Bimetallic TMP is utilized due to redox reactions in EC and catalytic activity in OE...
On the theory of internal photoemission in heterojunctions
Aslan, B; Turan, Raşit (Elsevier BV, 2005-08-01)
The theory of internal photoemission in semiconductor heterojunctions has been reviewed and the existing model has been extended by incorporating the effects of the difference in the effective masses in the active region and the substrate, non spherical-nonparabolic bands, and the energy loss per collisions. This complete model has been applied to describe the experimental results obtained from Si1-xGex/Si heterojunction infrared photodetectors. The barrier heights (correspondingly the cut-off wavelengths) ...
Citation Formats
B. İpek Torun and D. Üner, On the Limits of Photocatalytic Water Splitting. 2019, p. 1.