Selective site occupancy exhibited by Cr3+ and Cr6+ incorporated into electrochemically deposited nickel hydroxide films

We have utilized extended X-ray absorption fine structure (EXAFS) spectrosc opy to investigate the site occupancy and local structure of Cr3+ and Cr6ions incorporated into electrodeposited alpha-Ni(OH)(2) films. The films we re prepared by codeposition of Cr and Ni at constant cathodic current from aqueous solutions of nickel nitrate, chromium nitrate, and potassium chroma te. EXAFS measurements show that in films produced from Ni2+ and Cr3+ solut ion, Cr3+ is incorporated into Ni lattice sites in alpha-Ni(OH)(2). On the other hand, cathodic codeposition of Cr6+ and Ni2+ results in CrO42- in int erlamellar sites as well as sorbed on the surface of alpha-Ni(OH)(2). These results are of significance in a number of technological areas, e.g., batt eries, corrosion protection, environmental speciation, and remediation. (C) 1999 The Electrochemical Society. S1099-0062(98)06-015-5. All rights reser ved.