Role of Transition Metal-Hydroxide (M-OHx , M=Mn, Fe, Ni, Co) Co-catalyst Loading : Efficiency and Stability of CdS Phot
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Role of Transition Metal-Hydroxide (M-OHx , M=Mn, Fe, Ni, Co) Co-catalyst Loading : Efficiency and Stability of CdS Photoanode Alka Pareek,1, 2 Pradip Paik2 and Pramod H. Borse1 1 Center for nanomaterials, ARCI, Balapur PO., Hyderabad, Telangana, India 2 SEST, Hyderabad Central University, Hyderabad, Telangana, India. ABSTRACT In this work we have synthesized the colloidal particles of transition metal-hydroxide (M= Ni, Co, Mn, Fe) by a simple chemical precipitation method. The surface of spray deposited CdS thin films were modified using nano-colloids to utlize them as water oxidation catalysts (WOC) for the photoelectrochemical cell (PEC). A systematic comparison of the PEC performance of modified and unmodified film is carried out to understand the role of co-catalyst. Ni(OH)2 modification yields 3.4 times higher photocurrent density than bare CdS photoanode, and exhibits hydrogen-evolution rate of 600 μmol/hr. Fe(OH)2 modified film shows best stability of 8 hours as compared to the others. INTRODUCTION Photoelectrochemical (PEC) cell is a reliable device for harnessing and converting abundant solar energy into hydrogen by making use of green path [1]. It’s been a challenge to identify a perfect semiconducting material, possessing all the desirable properties of a photoanode for a PEC cell. Cadmium sulphide is one of the most suitable and studied PEC material. This is due to its capability to absorb the visible light photons (E~1.5eV – 3eV), which displays the band-edge positions that suits for water-splitting reaction (H2O→H2+O2). However, the dissolution of CdS in electrolyte during the photo-illumination (termed as photocorrosion) is a major drawback [2]. There are different methods to improve the stability and efficiency of CdS photoanodes viz. heterostructure, nanostructuring loading of cocatalysts etc. One of the practical methods to inhibit photocorrosion over the semiconductor surface is loading of the water oxidation cocatalyst (WOC). The role of WOC’s lies in increasing the water oxidation kinetics by reducing the overpotential at junction; which then releases the excess photogenerated holes on the semiconductor surface [3]. In past, inert metals (Pt, RuO2, Ru) had been used to improve the efficiency and stability of CdS photoanodes [4]. Commercially, usage of such materials is uneconomic option for any technological usage. Recently, transition metal-hydroxides and metaloxides (M-OH; M=Co, Ni, Cu, Mn) are emerging as cost-effective, abundant and robust WOCs [5-7]. In present work, we have loaded nano-sized metal hydroxides on the surface of CdS by chemical impregnation method. Such modified electrodes show an enhanced photocurrent, as well as stability that improved to several hours. The work shows promise of WOC’s in achieving an improvement in the performance and stability of the PEC cell for desirable technological applications
EXPERIMENT Deposition of CdS thin films An automated spray pyrolysis method was used for the deposition of CdS thin films. Several optimizations were done to get nanostructu
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