Photoelectrochemical Hydrogen Evolution and CO2 Reduction over MoS2/Si and MoSe2/Si Nanostructures by Combined Photoelectrochemical Deposition and Rapid-Thermal Annealing Process

Sungmin Hong,Choong Kyun Rhee,Youngku Sohn

doi:10.3390/catal9060494

Sungmin Hong, Choong Kyun Rhee + Show 1 more

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https://doi.org/10.3390/catal9060494

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Journal: Catalysts	Publication Date: May 28, 2019
Citations: 18	License type: CC BY 4.0

Affiliation: Chungnam National University

Abstract

Diverse methods have been employed to synthesize MoS2 and MoSe2 catalyst systems. Herein, a combined photoelectrochemical (PEC) deposition and rapid-thermal annealing process has first been employed to fabricate MoS2 and MoSe2 thin films on Si substrates. The newly developed transition-metal dichalcogenides were characterized by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. PEC hydrogen evolution reaction (HER) was demonstrated in an acidic condition to show a PEC catalytic performance order of MoOx/Si < MoS2/Si << MoSe2/Si under the visible light-on condition. The HER activity (4.5 mA/cm2 at −1.0 V vs Ag/AgCl) of MoSe2/Si was increased by 4.8× compared with that under the dark condition. For CO2 reduction, the PEC activity was observed to be in the order of MoS2/Si < MoOx/Si << MoSe2/Si under the visible light-on condition. The reduction activity (0.127 mA/cm2) of MoSe2/Si was increased by 9.3× compared with that under the dark condition. The combined electrochemical deposition and rapid-thermal annealing method could be a very useful method for fabricating a thin film state catalytic system perusing hydrogen production and CO2 energy conversion.

Highlights

Transition-metal dichalcogenides (TMDCs) have widely been studied for applications to energy and environment such as hydrogen evolution and CO2 reduction [1,2,3,4,5,6,7,8,9,10]
For CO2 reduction, the PEC activity was observed to be in the order of MoS2 /Si < Mo oxides (MoOx) /Si
Ye et al employed a chemical vapor deposition (CVD) method to synthesize monolayer MoS2 followed by oxygen plasma treatment or hydrogen annealing

Summary

Introduction

Transition-metal dichalcogenides (TMDCs) have widely been studied for applications to energy and environment such as hydrogen evolution and CO2 reduction [1,2,3,4,5,6,7,8,9,10]. Molybdenum disulfide and diselenide (MoS2 and MoSe2 ) materials with two-dimensional character have been synthesized using diverse synthesis methods for their applications [11]. Ye et al employed a chemical vapor deposition (CVD) method to synthesize monolayer MoS2 followed by oxygen plasma treatment or hydrogen annealing. They showed that hydrogen evolution reaction (HER) activity (e.g., onset potential and current density) was increased substantially by engineering the defects [12]. HER activity of MoS2 or MoSe2 , various defect engineering techniques have been employed, which include laser irradiation [13], ion irradiation [14,15] and NaClO chemical etching [16]. Li et al examined various defect sites of MoS2 such as edge sites, S vacancies and grain boundaries and showed that edge sites and S vacancies (with optimal vacancy density of 7–10%) were main HER active sites [17]

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