Mono- and Bimetallic Silver-Containing Nitrogen-Doped Carbon Composites and Their Electrocatalytic Activity

Abstract

The N-doped metal-carbon composites based on the carbonized melamine-formaldehyde polymer (MFP) with silver, silver-copper, and silver-cobalt particles were synthesized. Mono- and bimetallic silver-containing composites were prepared by the reduction of metal nitrates with hydrazine hydrate in an aqueous ethanol medium in the presence of carbon black particles obtained by the heat treatment of MF-polymer at 500 °C. The structural-phase changes before and after the use of metal-carbon composites as electrocatalysts in the electrohydrogenation of p-nitroaniline (p-NA) were studied by X-ray diffraction analysis. The morphological features of the created MFBC + Ag, MFBC + (Ag+Cu) and MFBC + (Ag+Co) composites were studied by electron microscopy. It was established that the synthesized composites mainly contain crystalline phases of the corresponding reduced metals or their alloys. The monometallic MFBC(1) + Ag(1) composite contains reduced silver crystallites of various shapes and localization on porous MF carbon black particles. Higher electrocatalytic activity of the synthesized Ag-containing composites in the p-NA electrohydrogenation was shown in comparison not only with the electrochemical reduction of p-NA but also with MFBC + (Ag+Cu) composites with electrocatalytic hydrogenation of p-NA on Ag + Cu particles (without MFBC). It was found that the use of the studied MFBC-composites increases the selectivity of the formation of the main hydrogenation product (p-phenylenediamine) and decreases the yields of by-products.