Electrochemical hydrogen evolution performance of molybdenum disulphide/HKUST-1 metal organic framework/polyaniline ternary nanocomposite in acidic medium
Kabelo E. Ramohlola, Miranda M. Ndipingwi, Kwena D. Modibane, Tshaamano C. Morudu, Edwin Makhado, Katlego Makgopa, Shaine Raseale, Mpitloane J. Hato, Emmanuel I. Iwuoha
Abstract
Abstract A search for an abundant and cheap electrocatalyst to replace the expensive and scarce precious metal-based electrocatalysts for hydrogen evolution reaction (HER) is critical for realization of hydrogen as an energy carrier. Herein, molybdenum disulphide-copper-based metal organic framework/polyaniline (MoS 2 /HKUST-1/PANI) ternary composite was synthesized following a simple in situ chemical oxidative polymerization of aniline in the presence of already hydrothermally synthesized MoS 2 and HKUST-1 pristine materials. Several analytical techniques were used to evaluation the formation and structure properties of the ternary composite. The X-ray photoelectron spectroscopy results were in agreement with the morphological and structural characterization techniques and further confirming the wrapping of MoS 2 and HKUST-1 by PANI. Optical studies displayed an increase of direct and indirect band gaps the ternary composite but closer to the one of PANI homopolymer suggesting that the ternary composite exhibited good conductivity, which is an essential property for HER. The electrochemical characterization presented that the ternary composite possessed a diffusion-controlled nature with a 12-fold increase in the electrochemical surface area of as compared to PANI homopolymer. The prepared MoS 2 /HKUST-1/PANI composite exhibited excellent HER properties with a Tafel slope of 44.7 mV.dec −1 and low charge-transfer resistance as well as turnover frequency of 4.0 mol H 2 per second at 750 mV potential versus reversible hydrogen electrode (RHE). Most importantly, it only needed 110 mV overpotential vs RHE to reach the current density of 10 mA.cm −2 . In addition, MoS 2 /HKUST-1/PANI ternary composite achieved superior stability over other prepared electrocatalysts. For the first time, employing MoS 2 and HKUST-1 to the backbone of polyaniline for the construction of the edge-rich integrative ternary nanocomposite has successfully achieved an outstanding HER performance. Graphical abstract