Vielstieh and U. VogeU: In a series of publications it has been shown by different investigators that during the anodic oxidation of formic acid in acid electrolytes an intermediate product is formed which blocks the surface in a certain potential region. A n odic potential scans show three current peaks (at 0.5, 0.8, and 1.3v v s . H2 electrode). In the region of the first peak the intermediate is formed; at the potential of the second peak the intermediate is oxidized to CO2.Rhodes and Steigelmann assume that the i n t e r m ediate product is carbon monoxide formed by catalytic decomposition of HCOOH into CO and H20. Potential scan diagrams with HCOOH and CO are performed in order to prove this hypothesis.In their experiments the authors observe a small difference (30 m v at a sweep rate of 1.2 v/sec, see their Table I) between the potential of the peak for CO and the potential of the second formic acid peak, especially during the first sweep, their Fig. 1 and 3. Nevertheless Rhodes and Steigelmann suggest that two peaks are caused by the oxidation of the same species.In our laboratory we have repeated the above m e ntioned experiment,2 recording the c u r r e n t / p o t e n t i a l diagrams (corresponding to their Fig. 1 and 3) on the same figure. This diagram (our Fig. 1) clearly shows: 1 I n s t i t u t f u e r P h y s i k a l i s c h e C h e m i e der U n i v e r s i t a e t B o n n , Wegelerstrasse 12, Bonn, G e r m a n y .W. V i e l s t i c h a n d U. Vogel, U n p u b l i s h e d results.(a) the difference in potential between the two peaks is v e r y pronounced and amounts to about 60 my; (b) the rising part of the CO peak is so sharp that due to adsorbed carbon monoxide only a v e r y small current should be possible in the region of the formic acid peak.In addition to the different shape of the c u r r e n t / potential diagrams there exists another strong argument against the assumption of carbon monoxide as intermediate product. Johnson and K u h n 3 have made a simultaneous determination of the n u m b e r of coulombs and the n u m b e r of chemical equivalents of reduced CO2; these species are identical with the intermediate product of formic acid oxidation. 4,5 Instead of the n u m b e r of 2 electrons per particle stated in the paper 3 one of the authors recently informed us that, due to an error in calculation, the true n u m b e r is one electron per particle. ~a Therefore, the results of Johnson and K u h n 3, 5a are in agreement with our own conclusion 4,5 that the intermediate product should be a formate radical, prob-O ably of the form --C \ OH D. R. Rhodes and E. F. Steigelmann:~The figure presented by Vielstich and Vogel does clearly show a s p . R. J o h n s o n a n d A. T. K u h n , This Journal, 112, 599 (1965). 4 W. V i e l s t i c h a n d U. Vogel, Bet. Bunsen Ges. Physikal. Chem., 68, 686 (1964). s W. Vielstich, " B r e n n s t o f f c l e m e n t e ---M o d e r n e V e r f a h r e n zur elekt r o c h e m i s c h e n E n e r g i e g e w i n n u n g , " Verl. C h e m i c , W e i n h...

No abstract

Formic acid in 1N H2804 at 30~ dissociatively adsorbs onto a platinum electrode to form a species that acts electrochemically like adsorbed CO. This species inhibits the oxidation of other compounds and, therefore, can act as a poison on an anode. It can be removed by anodic oxidation at relatively positive potentials. These effects were studied using a potential-sweep technique.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35

No abstract

The effect of 2537Aå ultraviolet light on the anodic oxidation of formic acid was examined in 1NH2SO4 electrolyte on a platinum gauze anode. At potentials more negative than 0.5v vs. SCE when the uv light is turned on, the current increases for a short time before it decreases to a near‐zero value. At potentials more positive than 0.5v, the current increases to a maximum value, the largest increase being at 0.65v vs. SCE. Most of the uv effects are due to the reaction of the photolysis products at the anode. At potentials more positive than 1.0v vs. SCE, electrode activation by uv light may be a factor.