1T-phase molybdenum disulfide (1T-MoS2) exhibits superior hydrogen evolution reaction (HER) over 2H-phase MoS2 (2H-MoS2). However, its thermodynamic instability is the main drawback impeding its practical application. In this work, a stable 1T-MoS2 monolayer formed at edge-aligned 2H-MoS2 and a reduced graphene oxide heterointerface (EA-2H/1T/RGO) using a precursor-in-solvent synthesis strategy are reported. Theoretical prediction indicates that the edge-aligned layer stacking can induce heterointerfacial charge transfer, which results in a phase transition of the interfacial monolayer from 2H to 1T that realizes thermodynamic stability based on the adhesion energy between MoS2 and graphene. As an electrocatalyst for HER, EA-2H/1T/RGO displays an onset potential of −103 mV versus RHE, a Tafel slope of 46 mV dec−1 and 10 h stability in acidic electrolyte. The unexpected activity of EA-2H/1T/RGO beyond 1T-MoS2 is due to an inherent defect caused by the gliding of S atoms during the phase transition from 2H to 1T, leading the Gibbs free energy of hydrogen adsorption (ΔGH*) to decrease from 0.13 to 0.07 eV, which is closest to the ideal value (0.06 eV) of 2H-MoS2. The presented work provides fundamental insights into the impressive electrochemical properties of HER and opens new avenues for phase transitions at 2D/2D hybrid interfaces.
Bibliographical noteFunding Information:
The authors acknowledge the grant by the National Research Foundation of Korea (NRF-2017M3A7B4041987, 2016M3D3A1A01913254, 2015M1A2A2074663). This work was also supported by National Natural Science Foundation of China (No. 51802175) and Natural Science Foundation of Jiangsu Province (BK20180493). The authors acknowledge Prof. SangHo Kim for assistance with TEM measurements and Prof. Xiaowei Sheng for assistance with DFT calculation.
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All Science Journal Classification (ASJC) codes
- Materials Science(all)