Lecture 15 Current-Potential Curves at Semiconductor Electrodes - Part II - Reference. 1.R. Memming, Semiconductor Electrochemistry, Wiley-VCH, 2000 (e-book) 2.A.J. Bard and L.R. Faulkner, Electrochemical Methods: Fundamentals and Applications, Wiley, J. O’M. Bockris, A.K.N. Reddy, and M. Gamboa-Aldeco, Modern Electrochemistry, Kluwer Academic/Plenum Publishers, 2000 Lecture note

Light-induced Process

Majority Carrier Reaction - Dark I-V Examples - 1.ln(j) vs. U E (is the  60 mV/dec.?) 2.Rate constant or charge transfer kinetics

ZnO in Water n-ZnO in water with various redox systems 1. pH dependence 2. Slope = 60 mV/dec. 3. Reaction rate constants k c,max - U 0 redox = 0.2 V and E s c = -0.2V for [Fe(CN) 6 ] 3-/4- - k - c from log j- vs.  sc  1.3  cm 4 s -1  k - c,max ~ cm 4 s -1  k + c,max ~ cm 4 s -1

n-InP in Methanol with Methyl Ferrocene 1. SC in non-aqueous solution  No interference associated with corrosion and H 2 evolution 2. Standard redox system  Ferrocene (F c 0/1+ ) and cobaltocene (CoC p2 0/1+ )  Non-adsorbing outer sphere redox systems 3. k - c,max ~ cm 4 s -1 for ferrocene k - c,max ~ cm 4 s -1 for cobaltocene

n-GaAs in Acetonitrile with Cobaltocene 1. Reduction of cobaltocene at GaAs electrode  Ultrafast charge transfer kinetics 2. I-V curve model by the thermionic model  What does it mean? 3. Charge transfer velocity S et (cm/s) S et = k - c N ad,ox ~ 5  10 6 cm/s

n-GaAs in Water (H 2 Formation) Hydrogen evolving reaction (HER) 1. 2H + + 2e - = H 2 U 0 redox = 0 V vs. NHE 2. 2H 2 O + 2e - = H 2 + 2OH - U 0 redox = V vs. NHE

Minority Carrier Reactions - Photo-effect -

n-WSe 2 in Water

p-GaAs in Water

Next Meeting Electrochemical Decomposition of Seminconductors