Separation Mechanism of a Photoinduced Electron‐Hole Pair in Metal‐Loaded Semiconductor Powders

Abstract

Metals J Photochemistry 1 Photoelectrochemistry J Semiconductors J SurfacesPhotocatalytic activities of metal loaded CdS and p-GaP semiconductor powders were measured for ammonia production from aqueous N, solution and hydrogen evolution from ethanol-water mixture. The higher activity was obtained for the CdS loaded with the metal having a higher work function. On the other hand, the metal-loading on p-GaP powders showed a slight increase in the activity with loading lower work function metals. The numerical calculation for two-dimensional Poisson equation shows that the electric field gradient is formed around the metal spots. This field gradient causes electrons to be captured by the metal, and holes to be collected on the semiconductor-solution interface between the metal spots.

Photoinduced transformations in semiconductor­metal nanocomposite assemblies

“…Noble metals deposited on the semiconductor particles have been shown to improve photocatalytic electron transfer processes at the semiconductor interface [18,25,[54][55][56]. As the hole transfer at the semiconductor/electrolyte is improved by the presence of a metal deposit we expect greater amounts of electron accumulation within the semiconductor nanocrystallites.…”

“…It has been shown that the photocatalytic electron transfer processes at the semiconductor interface can be greatly enhanced by depositing a noble metal on the semiconductor particle [18,25,[54][55][56]. The photogenerated holes are capable of oxidizing thiocyanate ions at the semiconductor interface [57].…”

Solar Water Splitting Using Semiconductor Photocatalyst Powders

“…Mass transfer of reactants Figure 3 summarizes the parameters that are highlighted according to the six processes. This review gives a broad and rather conceptual description only, rather than detailed discussion on the specific materials, which can be found in different reviews [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. The author trusts that the understanding of these physicochemical properties leads to "photocatalyst materials by design" where the electronic structure of the semiconductor, interface development, and electrocatalytic properties are fully connected to achieve the complex sequential processes to achieve finally overall water splitting.…”

Toward Visible Light Response: Overall Water Splitting Using Heterogeneous Photocatalysts

“…In semiconductors, one of the driving forces of charge transfer is band bending. Figure 3 depicts the band bending that occurs when an n-type semiconductor is in contact with a solution [7]. In this case, the majority charges (electrons) near the interface of the semiconductor transfer into the solution until the potentials are equilibrated; i.e., the Fermi level (E F / equals the redox potential (E redox ) in the solution while preserving the band edge positions (pinning).…”

“…The H 2 O splitting is rather special case where chemical potential of electrons in the electrolyte may vary in between the H C /H 2 and the O 2 /H 2 O redox potentials. The figure gives a concept of Schottky barrier formation [7,8], extent of which is influenced by the Fermi level of semiconductor and the work function of the metals. In comparison with the bare semiconductor surface that is positively charged, metal particles are relatively negatively charged, enhancing the charge separation.…”