ADSORPTION OF 2-AMINO-5-NITROPYRIDINE ON THE (111) AND (210) SILVER FACES

The adsorption isotherms of 2-amino-5-nitropyridine (ANP) on the (111) and (210) silver faces from an aqueous solution of 0.09 M KClO4 + 0.0 2 M NaOH were determined at -0.4 V vs. the 1 mol l-1 calomel electrode using double-potential-step chronocoulometry. The surface concentrati on GAMMA(ANP) Of ANP was obtained by stepping the applied potential fr om -0.4 V, where ANP is electroinactive, to -1.2 V, where ANP is elect roreduced to 2,5-diaminopyridine. The charge involved in this step, on ce corrected for the diffusive and capacitive contributions, yields 6F GAMMA(ANP) directly. The maximum surface concentration and standard Gi bbs energy of adsorption are equal to 3.6 x 10(-10) mol cm-2 and -35 k J mol-1 on Ag(111) and 5.2 x 10(-10) mol CM-2 and -42 kJ mol-1 on Ag(2 10), thus demonstrating the strong effect of surface crystallography o n the energetics of ANP adsorption.