MoS2-Carbon Inter-overlapped Structures as Effective Electrocatalysts for the Hydrogen Evolution Reaction

Po-Chia Huang; Chia-Ling Wu; Sanjaya Brahma; Muhammad Omar Shaikh; Jow-Lay Huang; Jey-Jau Lee; Sheng-Chang Wang

doi:10.3390/nano10071389

MoS₂-Carbon Inter-overlapped Structures as Effective Electrocatalysts for the Hydrogen Evolution Reaction

Nanomaterials (Basel). 2020 Jul 17;10(7):1389. doi: 10.3390/nano10071389.

Authors

Po-Chia Huang¹, Chia-Ling Wu², Sanjaya Brahma², Muhammad Omar Shaikh³, Jow-Lay Huang², Jey-Jau Lee¹, Sheng-Chang Wang⁴

Affiliations

¹ X-ray Scattering Group, National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan.
² Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan.
³ Institute of Medical Science and Technology, National Sun Yat-sen University, Kaohsiung 804, Taiwan.
⁴ Department of Mechanical Engineering, Southern Taiwan University of Science and Technology, Tainan 710, Taiwan.

Abstract

The ability to generate hydrogen in an economic and sustainable manner is critical to the realization of a future hydrogen economy. Electrocatalytic water splitting into molecular hydrogen using the hydrogen evolution reaction (HER) provides a viable option for hydrogen generation. Consequently, advanced non-precious metal based electrocatalysts that promote HER and reduce the overpotential are being widely researched. Here, we report on the development of MoS₂-carbon inter-overlapped structures and their applicability for enhancing electrocatalytic HER. These structures were synthesized by a facile hot-injection method using ammonium tetrathiomolybdate ((NH₄)₂MoS₄) as the precursor and oleylamine (OLA) as the solvent, followed by a carbonization step. During the synthesis protocol, OLA not only plays the role of a reacting solvent but also acts as an intercalating agent which enlarges the interlayer spacing of MoS₂ to form OLA-protected monolayer MoS₂. After the carbonization step, the crystallinity improves substantially, and OLA can be completely converted into carbon, thus forming an inter-overlapped superstructure, as characterized in detail using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). A Tafel slope of 118 mV/dec is obtained for the monolayer MoS₂-carbon superstructure, which shows a significant improvement, as compared to the 202 mV/dec observed for OLA-protected monolayer MoS₂. The enhanced HER performance is attributed to the improved conductivity along the c-axis due to the presence of carbon and the abundance of active sites due to the interlayer expansion of the monolayer MoS₂ by OLA.

Keywords: MoS2-carbon; electrocatalysis; hot-injection method; layer-expanded.