LVII. Differential Photocurrent and Second Harmonic Techniques for in situ Monitoring of Surface States on n-MoSe2 in Aqueous Solutions

نویسندگان

  • Bob L. Wheeler
  • Allen J. Bard
چکیده

Second harmonic ac impedance and differential photocurrent techniques are employed to monitor, in situ, the surface states on n-MoSes electrodes in aqueous solutions containing the Fe(CN)6 s-/4couple. These two techniques are qualitatively more sensitive to the presence of surface states on single-crystal n-MoSes than first harmonic ac techniques. Surface states on this semiconductor electrode were passivated by a thin layer of RuOx. This film also increased the PEC efficiency of both single-crystal and polycrystalline n-MoSes. Surface states, either intrinsic or extrinsic, are known to affect the performance of photoelectrochemical (PEC) cells and behavior of semiconductor electrodes by promoting Fermi level pinning, acting as recombinat ion centers, and abetting dark current flow (1-3). Several techniques for the study of surface states at electrode surfaces contacting electrolyte solutions are available; these include (i) current-potential methods (3), (ii) photocapacitance spectroscopy (4), (iii) electroluminescence spectroscopy (5-7), (iv) photoluminescence spectroscopy (7), (v) measurements of the subbandgap photoresponse (8-10), (vi) interfacial capacitance (11), and (vii) surface photovoltage (12). Recently, we reported that the ac impedance technique can provide information about both the energy distribution and density of surface states (13, 14). This method could detect the presence of surface states even when their density was too small to cause Fermi level pinning on n-MoTes. We report here ac impedance studies of n-MoSes and demonstrate the use of this method as a means of in situ monitoring of the semiconductor surface and the effects of surface treatments. In addition, two techniques are described which are qualitatively even more sensitive to the presence of surface states: the second harmonic ac impedance and the differential photocurrent techniques. Deposition of a thin layer of R u O / o n the surface of n-MoSes was shown by all three techniques to passivate the surface states present. Concurrently, the photocurrent-voltage behavior showed a dramatic improvement. This provides strong evidence that all three techniques monitor the semiconductor surface, in situ, and that the surface states were responsible for the poor photocurrent-voltage behavior with the untreated surface. The improvement of the single-crystal behavior encouraged us to at tempt to improve polycrystalline MoSes films by the same method.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Effect of Additional Hydroxyl Group On Dissolution Of Azo Dyes derived from N-carboxylic acid-1,8-naphthalimide in aqueous solutions containing various surface active agents

Dissolution of azo dyes derived from N-carboxylic acid-1,8-naphthalimide was studied in aqueous solutions containing formaldehyde condensation of naphthalenesulphonic acid and fatty alcohol ethylene oxide compound surfactants and effect of additional hydroxyl group on chemical structure of dye on dissolution was investigated. In addition, the effect of important factors on dissolution of used d...

متن کامل

Study of Photo-Conductivity in MoS2 Thin Films Grown in Low-Temperature Aqueous Solution Bath

An experimental study over the optical response of thin MoS2 films grownby chemical bath deposition (CBD) method is presented. As two important factors, theeffect of bath temperature and growth time are considered on the photocurrentgeneration in the grown samples. The results show that increasing the growth time leadsto better optical response and higher difference betw...

متن کامل

Enhanced removal of humic acids (HAs) from aqueous solutions using MWCNTs modified by N-(3-nitro-benzylidene)-N-trimethoxysilylpropyl-ethane-1,2-diamine on Equilibrium, thermodynamic and kinetics

In this study, multi-walled carbon nanotubes modified by N-(3-nitro-benzylidene)-N-trimethoxysilylpropyl-ethane-1, 2-diamine (NBATSPED-MWCNTs) was prepared as a low-cost and non-toxic adsorbent. These  materials was characterized by different techniques such as SEM, XRD and FT-IR and subsequently was used for the removal of humic acids (HAs) from aqueous solution. The influence of various opera...

متن کامل

Modeling and Optimization of Arsenic (III) Removal from Aqueous Solutions by GFO Using Response Surface Methodology

Arsenic is a highly toxic element for human beings, which is generally found in groundwater. Dissolved Arsenic in water can be seen as As+3 and As+5 states. The adsorption process is one of the available methods to remove Arsenic from aqueous solutions. Thus, this papers aims at removing Arsenic (III) from aqueous solutions through adsorption on iron oxide granules. The relation among four inde...

متن کامل

Modeling and Optimization of Arsenic (III) Removal from Aqueous Solutions by GFO Using Response Surface Methodology

Arsenic is a highly toxic element for human beings, which is generally found in groundwater. Dissolved Arsenic in water can be seen as As+3 and As+5 states. The adsorption process is one of the available methods to remove Arsenic from aqueous solutions. Thus, this papers aims at removing Arsenic (III) from aqueous solutions through adsorption on iron oxide granules. The relation among four inde...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2005