Improvement of performances of complex non-platinum electrode materials for hydrogen evolution

Abstract

Structural and electrochemical characteristics of hypo-hyper d-electrocatalytic materials aimed for preparation of electrodes for hydrogen evolution were studied and modified in order to improve their performances. All studied materials were of general composition 10% Ni + 18% TiO 2 + C.All materials were prepared of amorphous or crystalline TiO 2 , crystalline Ni or NiCo (10-20 nm) and Vulcan XC-72, by sol-gel procedure. Both, material's intrinsic catalytic activity and surface area were affected by applied modifications. As a result, the electrocatalytic activity was improved, e.g. transformation of TiO 2 into anatase form lowers the HER overpotential for 60 mV. Introduction of MWCNTs was even more effective, lowering η for 120 mV. Co addition to metallic phase lowers η for utmost 195 mV.Combined modification of TiO 2 and carbon substrate lowers η for 145 mV, while the complete modification of all three catalyst's components was the most effective with 230 mV decrease of overpotential.

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

“…3 are SEM microphotographies of some characteristic catalysts. Generally, the morphology of these catalysts is very similar to that of Ni-based catalysts studied in the previous work [12]. The catalyst's particles deposited on Vulcan are of a spherical shape (Fig.…”

“…A general conclusion of the results for the Ni-based hypo-hyper d-systems presented in our previous work [12] was that addition of Co into hyper d-metallic phase has the highest contribution to the improvement of catalytic activity of the basic Ni-catalyst. That was why we decided to move on investigation of Co-based systems.…”

“…HER overpotential is for 205 mV lower on basic Co-catalyst (sample 2) than on the corresponding Ni-based catalyst (10% Ni + TiO 2 (250 • C) + Vulcan XC-72) [12]. This is result of very small size of Co grains (high developed surface area) as active catalytic centers and their high dispersion over the catalyst's surface.…”

“…They are so small (lower than 2 nm) and uniformly dispersed over the surface so that high activity is achieved even in the stage of basic catalyst and there is no left possibility for significant increase due to the transformation of TiO 2 into crystalline shape. Situation is quite different with Ni-based systems where basic catalyst is not so active and there is a possibility for HER overpotential decrease for 60 mV at 60 mA cm −2 [12].…”

“…In our previous work [12] Ni-based catalysts were studied in order to determine the effect of modifications. It was found out that addition of Co into Ni metallic phase had the highest contribution to the rise of catalytic activity.…”