Hydrogen electrosorption in nanocrystalline Ti-based alloys

The electrochemical behavior in alkaline solution (1 M NaOH) of nanocrystal line Ti:Ru:Fe:O (2:1:1:2) prepared by high-energy ball milling was studied over its whole electroactivity domain, with a particular emphasis on the hy drogen evolution reaction (her). Comparison has also been made with nanocry stalline Ti:Ru:Fe (2:1:1) and a mixture of Ti:TiO:Ru:Fe2O3 (3/2:1/2:1:1/2). It was shown by cyclic voltammetry, open circuit potential decay and chron opotentiometry measurements that hydrogen absorption in the electrode mater ial occurs during hydrogen discharge. The electrochemical behavior of nanoc rystalline Ti:Ru:Fe:O (2:1:1:2) closely follows that of Ti:Ru:Fe (2:1:1), b ut differs radically from that of Ti:TiO:Ru:Fe2O3 (3/2:1/2:1:1/2). This is due to the fact that the former two compounds contain a significant fractio n of B2 phase (59 and 97 wt.%, respectively), while the latter does not. In steady state conditions, the ratio H/B2 phase in nanocrystalline Ti:Ru:Fe: O (2:1:1:2) is 0.15, about 1.6 times less than that for the O-free nanocrys talline compound. The coefficient of diffusion of hydrogen in nanocrystalli ne Ti:Ru:Fe:O (2:1:1:2) is 2.6 x 10(-13) cm(2) s(-1), more than three times less than that in nanocrystalline Ti:Ru:Fe (2:1:1). The difference between the hydrogen absorption characteristics of both nanocrystalline compounds are tracked down to the fact that their B2 phases have different stoichiome tries. (C) 2000 Elsevier Science S.A. All rights reserved.