Re: Helmholtz Layer electrode

[Frederick Sparber]

These Ellingham Diagrams make life simpler.

 

http://www.chem.mtu.edu/skkawatr/Ellingham.pdf

 

 

----- Original Message -----

From: Frederick Sparber

To: vortex-l

Sent: 5/30/2006 3:51:09 AM

Subject: Re: Helmholtz Layer electrode

It gets complicated.

http://environmentalchemistry.com/yogi/periodic/Ni.html

http://article.pubs.nrc-cnrc.gc.ca/ppv/RPViewDoc?_handler_=HandleInitialGet&journal=cjc&volume=53&calyLang=fra&articleFile=v75-464.pdf

Hydrogen-Water Deuterium Exchange Over Metal Oxide Promoted

Nickel Catalysts

Research Chemistry Branch, Atomic Energy of Canada Limited, Whiteshell Nuclear Research Establishment, Pinawa,

Manitoba ROE 1LO

"Specific rates have been measured for hydrogen-water deuterium isotope exchange over

unsupported nickel promoted with about 20% of various metal oxides. The oxides used were

Cr,03, MOO,, MnO, W0,-WO,, and UO,. Nickel surface areas, which are required to measure

the specific rates, were determined by hydrogen chemisorption. Specific rates were measured as

a function of temperature in the range 353 to 573 K and as a function of the partial pressure of

hydrogen and water over a 10-fold range of partial pressure.

The molybdenum and tungsten oxides gave the highest specific rates, and manganese and

uranium oxides the lowest. Chromium oxide was intermediate, although it gave the highest rate

per gram of catalyst. The orders with respect to hydrogen and water over molybdenum oxide and

tungsten oxide promoted nickel were consistent with a mechanism in which nickel oxide is

formed from the reaction of water with the catalyst, and then is reduced by hydrogen. Over

manganese and uranium oxide promoted catalysts, these orders are consistent with a mechanism

in which adsorbed water exchanges with chemisorbed hydrogen atoms on the nickel surface.

Chromium oxide is intermediate. It was noted that those oxides which favored the nickel oxide

route had electronic work functions closest to those of metallic nickel and nickel oxide."

http://forschung.unibw-muenchen.de/papers/pyusbmtfnscflbmt8ddnfrufeu9hdx.pdf

Basics of Reproducible Work Function Gas Sensing with Metal Oxides under

Environmental Conditions

"It is known that work function measurements on cleaved metal and metal oxide are strongly influenced by

crystal orientation and surface defects. Therefore using metal oxide layers in work function sensors has

been considered to be too problematic with regard to reproducibility. This study proves reproducible work

function measurements on a first set of metal oxides. A comparison on NiO, In2O3 and Fe2O3 layers shows

that stable, material specific gas sensitivities can be achieved which are to some extent independent of

microscopic surface properties."