Effect of duty cycle on NiMo alloys prepared by pulsed electrodeposition for hydrogen evolution reaction

Abstract

We report the influence of duty cycle in the range 30–70%, on NiMo alloys prepared on 316L stainless steel/Ni by pulsed electrodeposition and the characterization of their composition, morphology, and electrocatalytic activity towards hydrogen evolution reaction in alkaline medium. The morphology and Mo content were affected by varying the duty cycle between 70% and 30%, obtaining twice the Mo content and a more globular structure in the NiMo alloys prepared with a 30% duty cycle. The material presented a crystalline structure with peaks corresponding to the Ni (111) and (200) planes, which are independent of the duty cycle used. The cyclic voltammetry analysis showed a remarkable increment of the exchange current density when increasing the Mo content. This effect was attributed to changes in the electronic structure related to the nanostructure of the material. All the NiMo alloys analyzed showed activation to hydrogen evolution reaction after ageing, being that obtained at 30% duty cycle the one that showed the highest one. By analysis of electrochemical impedance spectroscopy, we found for duty cycle 70% a behaviour similar to that of NiMo synthesized by direct current techniques. In that catalyst, two processes were observed at different potentials while the NiMo30% catalyst shows several electrochemical processes occurring.