Emerging clay-aryl-gold nanohybrids for efficient electrocatalytic proton reduction

Abstract

There is an ever growing demand for renewable sources of energy to replace conventional fossil fuels. One of the alternatives is usage of hydrogen production by electrochemical hydrogen evolution reaction (HER). Toward this end, we have successfully prepared a novel, robust electrocatalyst for HER containing Au nanoparticles dispersed on a natural bentonite using a simple one-pot reduction process. It is one of the most effective ways to minimize Au nanoparticle production cost, stability and usage.

Bentonite clay was first modified using two coupling agents (mercaptosilane (MPS) or the diazonium salt of diphenyl aminoaniline (DPA)) to increase interlamellar spacing distance and to provide anchoring sites for the perfluorinated diazonium tetrachloroaurate (III) salt used as a unique source of zero-valent gold nanoparticles dispersed on bentonite surface. Successful intercalation was confirmed by the detection of F1s peak in X-ray photoelectron spectroscopy (XPS) at ∼689 eV, in line with fluorine in CF bonds, and the reduction of gold (III) into metallic gold. Both nanohybrids showed efficient electrochemical activity for HER in acidic condition (0.1 M H2SO4) with high current density up to −25 mA.cm−2 at −1 V and 0.148 mV onset. Negligible decreasing in current density and slight shift in onset was observed after 1000 cycles. The results obtained so far open new avenues for the preparation of low cost, efficient and stable HER catalyst on the one hand, and will contribute to the knowledge of the surface chemistry of the diazonium salts, on the other hand.