Facile Synthesis of Molybdenum Diselenide Layers for High-Performance Hydrogen Evolution Electrocatalysts.

Dhanasekaran Vikraman,Kamran Akbar,Seung Hu Lee,Hyun-Seok Kim,Hui Joon Park,Kathalingam Adaikalam,Jongwan Jung,Seung-Hyun Chun,Sajjad Hussain

doi:10.1021/acsomega.8b00459

Abstract

A cost-effective solution-based synthesis route to grow MoSe2 thin films with vertically aligned atomic layers, thereby maximally exposing the edge sites on the film surface as well as enhancing charge transport to the electrode, is demonstrated for hydrogen evolution reaction. The surface morphologies of thin films are investigated by scanning electron microscopy and atomic force microscopy, and transmission electron microscopy analyses confirm the formation of the vertically aligned layered structure of MoSe2 in those films, with supporting evidences obtained by Raman. Additionally, their optical and compositional properties are investigated by photoluminescence and X-ray photoelectron spectroscopy, and their electrical properties are evaluated using bottom-gate field-effect transistors. The resultant pristine MoSe2 thin film exhibited low overpotential of 88 mV (at 10 mA·cm–2) and a noticeably high exchange current density of 0.845 mA·cm–2 with excellent stability, which is superior to most of other reported MoS2 or MoSe2-based catalysts, even without any other strategies such as doping, phase transformation, and integration with other materials.

Highlights

As the interest in hydrogen (H2) has continuously increased as a future sustainable energy source because of its high energy density without environmental pollution,[1,2] massive efforts have been devoted to develop efficient processes for H2 production
In recent years, layered transition metal dichalcogenides (TMDCs) such as MoS2 and MoSe2 have received great attention by showing their potentials as efficient electrocatalysts for the hydrogen evolution reaction (HER),[7−41] and their cost-effectiveness, chemical stability, and profusion further support their extension to future earth-abundant noble-metal-free electrocatalysts
The synthesis of vertically aligned MoSe2 layers was achieved on different substrates (SiO2/Si and Au/Si) using a cost-effective chemical bath deposition (CBD) method.[45]

Summary

Introduction

As the interest in hydrogen (H2) has continuously increased as a future sustainable energy source because of its high energy density without environmental pollution,[1,2] massive efforts have been devoted to develop efficient processes for H2 production. Each charge-neutral layer of TMDCs, which consists of covalently bonded three atomic sheets (e.g., center Mo- and adjacent two S-sheets in MoS2), is stacked together by weak out-of-plane van der Waals interactions to form bulk-state. Those layered materials have two types of surfaces, which are terrace sites on the basal planes and edge sites on the side surfaces, providing highly anisotropic property including hydrogen adsorption free energy on each surface, ΔGH, for HER. Improving the catalytic activity of both basal and edge planes by transforming semiconducting 2H phase to 1T metallic phase (e.g., lithium intercalation) has been acknowledged to improve the HER performance of TMDCs,[16,17,25,31,39] but the process is cost-

Methods

Results

Conclusion