Mo-MoSe₂ Core-shell Nanostructures For Hydrogen Evolution Reaction

The necessity of new sources for greener and cleaner energy production is increasingly growing over the years in order to replace the existing ones. Between those, the hydrogen evolution reaction（HER） has a large potential. Although theoretical studies have shown the potential of TMDs for HER because of their catalytic activity at the edge sites, only few experimental reports of TMDs with a low Tafel slope of reaching to 38 mV/dec have been achieved because of the limitation by the electrochemical desorption（Heyrovsky reaction）.In this work, we demonstrate MoSe₂/Mo core-shell hierarchical nanostructures from Mo hierarchical nanostructures through a low temperature plasma selenization process with controlled shapes deposited by glancing angle deposition system（GLAD）. Three different nanostructures nanohelices, nanoscrews and nanorods were achieved when engineering the deposition parameters. And the surface area of nanosrews is the largest, which is 4.59 times than flat Mo. The 1T-MoSe₂/Mo core-shell hierarchical nanostructures can be achieved at the selenization temperature as low as 400 oC, while phase of 2H-MoSe₂/Mo core-shell hierarchical nanostructures are dominated once the selenization temperature over 500 oC. The 1T-MoSe₂/Mo core-shell hierarchical nanoscrews provide more edge sites to enhance HER with the Tafel slope as low as 34.7 mV/dec, clearly dominated by a Volmer-Tafel reaction, which is close to the theoretical value of 29 mV/dec for the ideal HER process, opening up a step forward in the development of low cost and high energy efficient catalyst for H2 production.This paper also compared the catalytic performance of different nanostructures and different selenization time, which confirmed that the nanoscrews selenized 8 minutes is optimal. In the end, comparing different height nanostructures, we verified the more active sites, the better HER catalytic performance.