The effects of iron coprecipitated into thin film nickel oxide electrodes or introduced in the 25 weight percent KOH electrolyte were studied by a combination of galvanostatic and open-circuit decay methods. Effects on voltammetric behavior and on the oxygen overpotential were observed in thin film electrodes with as little as 0.01% iron present. The overpotential was further lowered by 1% iron to the extent that the nickel oxide charge storage reaction was adversely affected. Higher concentrations of iron coprecipitated into a composite iron/nickel hydrous oxide dramatically catalyzed the oxygen evolution reaction by lowering the Tafel slope from about 70 mV/decade with no iron present to about 25 mV/decade with 10-50% iron. This composite oxide shows promise as an anodic electrocatalyst for alkaline electrolysis to produce hydrogen; the oxygen overpotential on thin film electrodes was over 200 mV lower than the overpotential with nickel oxide, itself, when polarized at 80 mA/cm 2. This work is part of a larger effort to understand the effects of various chemical additives and impurities on the performance of nickel oxide I charge storage electrodes. The specific interest here is on the effect of iron impurities which can poison the nickel oxide active material particularly in nickel-iron batteries (1) but also in other nickel batteries (2). Since iron has a lower oxygen overpotential than nickel (3), iron is thought to exert its effect by catalyzing the oxygen evolution reaction which is a parasitic side reaction during charge. The present work contributes some quantitative measurements of the effect of iron concentration on the oxygen evolution overpotential and the discharge capacity of thin film nickel oxide electrodes,The work here was originally directed towards battery applications. Thus, the electrolyte, the electrode preparation, and the electrochemical procedures used were chosen to be most relevant to sintered nickel oxide battery electrodes. However, a potentially more important application of this work is to oxygen evolving anodes for the electrolytic production of hydrogen. Some predict that future use of hydrogen as a fuel may dwarf the present market for hydrogen in the fertilizer, chemical, and metallurgical industries (4, 5). Electrolysis is an attractive process for hydrogen production when cheap electrical power is available. The present work with composite oxides of iron and nickel impacts on a major source of inefficiency in commercial electrolyzers, the oxygen overpotential at the nickel anodes customarily used (6). We have previously reported exceptionally strong catalytic properties for the evolution of oxygen and the possible utilization of these properties for alkaline electrolysis (7). Subsequently, another report has confirmed the exceptional catalytic properties of these materials (8). The present paper presents a more detailed picture of the oxygen evolution kinetics on composite hydrous oxides of iron and nickel with a view towards electrolysis applications. ExperimentalElectrolyt...

Binary 9:1 composite hydroxides of nickel with 13 other metals were prepared by cathodic electrocoprecipitation from metal nitrate solutions and characterized by cyclic voltammetry in 1M KOH. Under these conditions, coprecipitated Ce, Fe, and La strongly catalyzed the oxygen evolution reaction. Converse]y, Cd, Pb, and Zn poisoned this reaction. The hydrogen evolution reaction was less affected by the coprecipitated metals; Ag and Pb had a catalytic effect on this reaction. Co and Mn shifted the nickel hydroxide redox potentials to more cathodic values. In contrast, Cd, Ce, Cr, Fe, La, Y, and Zn each shifted these redox potentials anodically. The coulombic efficiency of the oxidation-reduction process was substantially lowered by Ce, Fe, and La.

Electrochemical and iodometric measurements on anodically charged thin film nickel hydroxide electrodes indicated an average nickel valence of 3.6 -+ 0.1. In situ visible spectroscopy of nickel hydroxide deposited on optically transparent electrodes featured one strong and broad absorption band with an intensity proportional to the state of charge. The results are not consistent with the presence of separate trivalent and quadrivalent phases or the participation of peroxide radicals in the nickel hydroxide redox reaction, but are best explained by the formation of a single mixed valence phase such as K(NiO2)3 9 xH20 which has a 3.67 average nickel valence. Full utilization of the proposed K(NiO2)3 9 xH20 oxidized phase could increase the discharge capacity of nickel battery electrodes by 67% beyond the previously assumed one-electron theoretical capacity. That the discharge is generally incomplete may be due to electronic isolation of portions of the oxidized material by a high resistivity layer of divalent nickel hydroxide produced at the surface during discharge.

This paper presents an overview and a detailed description of the key logic steps and mathematical-physics framework behind the development of practical algorithms for seismic exploration derived from the inverse scattering series. There are both significant symmetries and critical subtle differences between the forward scattering series construction and the inverse scattering series processing of seismic events. These similarities and differences help explain the efficiency and effectiveness of different inversion objectives. The inverse series performs all of the tasks associated with inversion using the entire wavefield recorded on the measurement surface as input. However, certain terms in the series act as though only one specific task,and no other task, existed. When isolated, these terms constitute a task-specific subseries. We present both the rationale for seeking and methods of identifying uncoupled task-specific subseries that accomplish: (1) free-surface multiple removal; (2) internal multiple attenuation; (3) imaging primaries at depth; and (4) inverting for earth material properties. A combination of forward series analogues and physical intuition is employed to locate those subseries. We show that the sum of the four taskspecific subseries does not correspond to the original inverse series since terms with coupled tasks are never considered or computed. Isolated tasks are accomplished sequentially and, after each is achieved, the problem is restarted as though that isolated task had never existed. This strategy avoids choosing portions of the series, at any stage, that correspond to a combination of tasks,i.e.,

Thin films of nickel hydroxide deposited on gold electrodes have been characterized in detail by in situ surface Raman spectroscopy in conjunction with electrochemical techniques. Raman spectra were obtained for film thicknesses varying from less than one equivalent monolayer to several hundred monolayers, as determined from the faradaic charge for the cyclic voltammetric oxidation of normalNifalse(OH)2 . For the thinnest films, Raman bands at 455 cm−1 and at 480 and 560 cm−1were obtained for the reduced and oxidized films, respectively, using 647.1 nm excitation at roughened gold. These signals, identified with Ni‐OH and Ni‐O vibrations from deuterium isotope data, were diagnosed as arising from surface‐enhanced Raman scattering (SERS) in view of their absence for the reduced film when using smooth gold surfaces and/or green/blue laser excitation. Raman spectra were obtained using the latter conditions for thicker oxidized films, which were consistent with resonance Raman scattering (RRS). Analysis of the dependence of the 480/560 cm−1 band intensities as a function of film thickness under conditions where SERS or RRS predominates enables the relative contributions of these mechanisms as well as the influence of film absorbance to be assessed quantitatively. Raman spectra were also obtained in air and after “film aging” by potential cycling or heating. The spectral changes following the latter treatments support the evolution of a less hydrogen‐bound normalNifalse(OH)2 film structure, i.e., the transformation of α‐normalto β‐normalNifalse(OH)2 . By combining cyclic voltammetry with analysis of the dissolved film using atomic absorption spectroscopy, the effective oxidation state of nickel in the oxidized films is determined to be +3.7 false(±0.1false) . On the basis of the spectroscopic and electrochemical measurements, the most likely structure for the oxidized film is a hydrated form of Mfalse(NiO2)3 , where M is the supporting electrolyte cation.