Synthesis and characterization of structured interfaces for hydrogen generation. Study of an N,N'-dialkyl-4,4'-bipyridinium redox polymer/palladium catalyst system

Journal Article · Thu Apr 29 00:00:00 EDT 1982 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100206a018· OSTI ID:6475333

Bruce, J A; Murahashi, T; Wrighton, M S

Structured interfaces for H/sub 2/ evolution have been synthesized and characterized. The substrates studied include W, Pt, and p-Si functionalized with N,N'-bis(3-(trimethoxysilyl)propyl)-4,4'-bipyridinium dibromide, I, to given polymeric quantities of a surface-confined N,N'-dialkyl-4,4'-bipyridinium (PQ/sup 2 +/) redox system, ((PQ/sup 2 +/)/sub n/)/sub surf/, (0.5 x 10/sup -8/ to 5 x 10/sup -8/ mol/cm/sup 2/) with an E/sup 0'/ of -0.55 +- 0.05 V vs. SCE, in aqueous electrolyte solution. Incorporation of Pd(0) (< 5 x 10/sup -8/ mol/cm/sup 2/) into the substrate/((PQ/sup 2 +/)/sub n/)/sub surf/ system leads to improvement of H/sub 2/-evolution kinetics for the W and p-Si electrodes. Various procedures have been used to prepare interfaces such as (i) substrate/Pd(0)/((PQ/sup 2 +/)/sub n/)/sub surf/ where Pd(0) coats the substrate and the ((PQ/sup 2 +/)/sub n/)/sub surf/ is an overlayer, (ii) substrate/((PQ/sup 2 +/)/sub n//Pd(0))/sub surf/ where the Pd(0) is only on the outermost surface, (iii) substrate/((PQ/sup 2 +/Pd(0))/sub n/)/sub surf/ where the Pd(0) is dispersed throughout the polymer overlayer, and (iv) substrate/((PQ/sup 2 +/)/sub n//Pd(0)/(PQ/sup 2 +/)/sub n/)/sub surf/ where the Pd(0) is sandwiched between two layers of polymer. Cathodes having no Pd(0) at the substrate/((PQ/sup 2 +/)/sub n/)/sub surf/ interface equilibrate with H/sub 2/O/H/sub 2/ only via the ((PQ/sup 2 +///sup +/)/sub n/)/sub surf/ redox couple, whereas Pd(0) in direct contact with the substrate can equilibrate the substrate with H/sub 2/O/H/sub 2/. Interface structures have been synthesized by deliberate electrochemical procedures and have been confirmed by Auger depth profile analyses. Current-voltage properties for the cathodes have been used to correlate structure with the H/sub 2/-evolution mechanism. Heavy metal impurity ions such as Hg/sup 2/+ and Pb/sup 2 +/ have been identified as an important source of deactivation of the catalytic activity of Pd(0).

• Research Organization: Massachusetts Inst. of Tech., Cambridge
• OSTI ID: 6475333
• Journal Information: J. Phys. Chem.; (United States), Vol. 86:9
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
BIPYRIDINES
CATALYTIC EFFECTS
SYNTHESIS
HYDROGEN PRODUCTION
PHOTOELECTROLYSIS
PALLADIUM
ELECTRODES
IMPURITIES
INTERFACES
ORGANIC POLYMERS
PHOTOELECTROCHEMICAL CELLS
SILICON
TUNGSTEN
AZINES
ELECTROCHEMICAL CELLS
ELECTROLYSIS
ELEMENTS
EQUIPMENT
HETEROCYCLIC COMPOUNDS
LYSIS
METALS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PLATINUM METALS
POLYMERS
PYRIDINES
SEMIMETALS
SOLAR EQUIPMENT
TRANSITION ELEMENTS
080106* - Hydrogen- Production- Biosynthesis &amp; Photochemical Processes