Development of Group 6 Transition Metal Carbides as Electrocatalyst

Abstract

Tungsten carbides-based electrocatalyts are prepared by carburization of tungsten with resorcinol-formaldehyde polymerization method. Their electrochemical properties are revealed by cyclic voltammetry and linear sweep voltammetry for hydrogen oxidation reaction and hydrogen evolution reaction. Physicochemical properties of electrocatalysts are investigated by SEM, TEM and BET analysis. Bimetallic tungsten carbides such as Ni, Nb, Ta and Fe are synthesized by same resorcinol-formaldehyde polymerization method. Various compositions of nickel tungsten carbides are successfully synthesized and they are used for support materials for ethanol oxidation reaction. Pd is loaded on tungsten carbides to improve electrochemical activity for hydrogen oxidation reaction and it shows much enhanced activity for hydrogen oxidation reaction and ethanol oxidation reaction. Furthermore, introduction of CNT and GR greatly enhanced activity of Pd/WC for hydrogen oxidation reaction. Other carbon fillers such as carbon nanotube and grapheme are introduced to tungsten carbides to improve overall electric conductivity of tungsten carbides and WC/CNT-GR shows best activity for hydrogen evolution reaction in terms of current and on-set potential. Mo2C, Mo2N, and MoS2 with carbon nanotube (CNT) – graphene (GR) composite are synthesized by modified-urea glass route. In our synthetic procedure, nanocrystalline Mo2C, Mo2N, and MoS2 are easily fabricated on the CNT-GR hybrid support by simple modification of the amount of urea or replacement of urea with thiourea. Apart from the activity comparison, the CNT-GR hybrid support, a composite between CNT and GR, is introduced to increase the HER activity of the loaded Mo-compounds by providing a large surface area and an excellent electron pathway. Mo2C, Mo2N, and MoS2 on CNT-GR hybrid are prepared by a simple synthetic method. By varying the amount of urea or replacing urea with thiourea, we could control the final phase. The activity comparisons among Mo2C, Mo2N, and MoS2 on CNT-GR composites are properly carried out by adopting a general synthetic method. Our non-precious metal catalyst, Mo2C/CNT-GR exhibits very high activity and durability for HER, which is one of the best performance using Mo-based catalysts.