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.

New nano-structured and interactive supported composite electrocatalysts for hydrogen evolution with partially replaced platinum loading

“…In all samples TiO 2 was detected as crystalline anatase [28] with crystallite size about 4 nm. Characteristic peaks of Co cannot be seen due to its amorphous character and very small particles [20,21]. Only in spectrum 1 (sample with pure Co as metallic phase) a very weak peak was indicated at 2q ¼ 44.22 , corresponding to (111) reflection of cubic Co [29].…”

“…The previous works of the present authors were concerned with production and characterization of so-called hypo-hyper d-electrocatalysts, containing 10% Me þ 18% TiO 2 þ carbon substrate [20][21][22]. Different metallic phases were studied such as Ni, Co or CoNi, deposited on both traditional Vulcan XC-72 and multiwalled carbon nanotubes (MWCNTs).…”

Effect of activation/purification of multiwalled carbon nanotubes (MWCNTs) on the activity of non-platinum based hypo-hyper d-electrocatalysts for hydrogen evolution

“…For illustration, it was shown in our previous work [11] that, in same experimental conditions, hydrogen evolution overpotential measured at Co-TiO 2 /MWCNTs(a) was 165 mV lower than that of Co/Vulcan XC-72 electrocatalyst (analogue to Pt/Vulcan XC-72) and 160 mV lower than that of Pt/Vulcan XC-72. The above confirms that remarkable improvement of catalytic activity is achieved by introducing TiO 2 and MWCNTs in the Cobased catalyst and by further activation of MWCNTs.…”

“…4. The only band of interest is that by TiO 2 , positioned at 495 cm À1 [11,30]. To determine the hypo-hyper d-interaction, the TiO 2 band from the electrocatalyst and the band from pure TiO 2 obtained in identical conditions as that in electrocatalyst need to be compared.…”

“…In our previous works [9][10][11], we investigated nano-scale hypohyper d-electrocatalysts containing Ni, Co or NiCo as hyper dphase and anatase titania as hypo d-phase, both deposited on carbon substrate. These multiwalled carbon nanotubes (MWCNTs) were compared to traditional carbon black (Vulcan XC-72) as carbon substrates.…”