The formation and behavior of Ag adsorbates at Pd electrodes and their influence on electrocatalytic oxidation of formic acid at Pd

Performance of the direct formic acid fuel cell with electrochemically modified palladium–antimony anode catalyst

“…There are three key effects. First, the coverage of less than one monolayer of catalyst with an adatom that is inert to formic acid isolates individual catalyst sites and reduces the amount of CO poison that can build up on the surface, particularly CO that is multiply bonded to the surface [63,64,68,[71][72][73][74][75][76]. This is known as the steric effect and is strongly supported by empirical evidence in which an adatom such as lead is shown to completely block CO buildup on platinum during formic acid oxidation [66].…”

Phase Separation in Electrodeposited Ag-Pd Alloy Films from Acidic Nitrate Bath

“…3b) exhibit large nucleation overpotential, suggesting that Ag + reduction could suppress the nucleation and growth of Pd-rich phases. 43…”

“…35 While underpotential deposition (UPD) of Pd 2+ and Ag + on Au substrates have been systematically investigated, [36][37][38][39][40][41] few papers discuss the UPD behavior of Ag at Pd or vice versa. Based on the model proposed by Kolb et al, the underpotential shift for Ag + on Pd should be 0.35 V. 41,42 In 1982, Koljadko et al investigated the adsorption of Ag at polycrystalline Pd electrodes in 5 mM Ag + sulfuric acid solution, concluding that Ag was adsorbed irreversibly with underpotential of 0.20 V. 43 UPD of 1 mM Ag + on Pd was also recently reported using mixed HNO 3 /H 2 SO 4 solution at 0.70 V RHE . 10 Ag + and Pd 2+ have close standard electrode potentials of 0.80 and 0.95 V SHE , respectively, 44 making it theoretically possible to switch the relative metal nobility by varying the concentration ratio or complexation.…”

Catalytic and electro-catalytic oxidation of formic acid on the pure and Cu-modified Pd(111)-surface

“…Studies on formic acid adsorption at transition metal surfaces have been performed since the 1970 s. Adsorption and reaction processes of formic acid have been investigated in UHV on poly-and single crystalline palladium [12][13][14][15][16][17] as well as on diverse other metal surfaces [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. Also the adsorption and decomposition of formic acid under electrochemical conditions at different metal surfaces in sulphuric or perchloric acid with formic acid concentrations below 1 mol l À1 have been described several times [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51], including, in particular, studies on the influence of foreign metal atoms deposited on polycrystalline palladium on the oxidation of formic acid [52][53][54][55]. The impact of deposited palladium monolayers on platinum has also been the subject of several investigations during t...…”