Electrocatalysis of the hydrogen evolution reaction by nanocomposites of poly(amidoamine)-encapsulated platinum nanoparticles and phosphotungstic acid

Poly( amidoamine) dendrimer ( Generation-4) encapsulated platinum nanoparticles (PtNP-PAMAM) were prepared and used to fabricate nanocomposites with Keggin-type phosphotungstic acid ( PW12O403-) using a layer by layer electrostatic assembly technique. Indium tin oxide ( ITO) electrodes, which were first modified with a monolayer of 3-aminopropyl triethoxysilane ( 3-APTES), were used as substrates for assembly of the PW12O403- monolayer. Nanocomposites were then fabricated by depositing PtNP-PAMAM on the monolayer of PW12O403-. The amount of PtNP-PAMAM deposited was controlled by using different concentrations of PtNP-PAMAM diluted in 0.1 M H2SO4 solution. The hydrogen evolution reaction ( HER) was used to test electrocatalytic activities of these nanocomposite modified electrodes. Modi. cation of ITO vertical bar 3-APTES with PW12O403-vertical bar PtNP-PAMAM showed significantly higher electrocatalytic activities toward the HER than electrodes modified with either PW12O403- or PtNP-PAMAM alone. The electrocatalytic activities were found to depend on the composition of PtNP-PAMAM and PW12O403- on electrode surfaces, which was attributed to an interaction between these species. Heat treatment of ITO vertical bar 3-APTES vertical bar PW12O403-vertical bar PtNP-PAMAM electrodes at 200 degrees C produced significantly higher electrocatalytic activities, which supported the suggestion of an interaction.