Study of structural and electrochemical characteristics of Co-based hypo–hyper d-electrocatalysts for hydrogen evolution

Abstract

Structural and electrochemical characteristics of hypo–hyper d-electrocatalytic materials aimed for preparation of electrodes for hydrogen evolution were studied. The basic catalytic material was prepared of 10% amorphous Co (grain size <2 nm), 18% amorphous TiO 2 and Vulcan XC-72, by sol–gel procedure. A number of modifications were applied aimed at improving the materials performances: (i) TiO 2 was transformed into anatase by heating at 480 °C for 1 h, (ii) multiwalled carbon nanotubes (MWCNT) were used as a catalyst support instead of Vulcan XC-72 and (iii) Mo was added to Co phase in a quantity of 25 at.% (Mo:Co = 1:3). Both, material's intrinsic catalytic activity and surface area were affected by these modifications. As a result, the electrocatalytic activity for hydrogen evolution was improved, e.g. transformation of TiO 2 into anatase form lowers the HER overpotential ( η) for 15 mV at 60 mA cm −2. Introduction of MWCNTs lowered η for 30 mV, while addition of Mo to metallic phase for 40 mV. The complete modification of all three catalyst's components (10% MoCo 3 + 18% anatase + MWCNTs) was the most effective with 60 mV decrease of overpotential. Characterization was made by XRD, SEM, IR and XPS methods. Surface area was measured by means of cyclic voltammetry.