Rational Design of Electrocatalytic Interfaces: The Multielectron Reduction of Nitrate in Aqueous Electrolytes

Abstract

An electrode incorporating two distinct heterogeneous electrocatalysts acting in series was specifically designed to promote the reduction of nitrate beyond the nitrite stage in weakly buffered aqueous solutions (pH = 3) containing Cd2+. This novel interface consists of Au nanoparticles, Au(np), on which underpotentially deposited Cd reduces nitrate predominantly to nitrite, dispersed on a hemin-modified glassy carbon (GC) surface, Hm|GC, where nitrite is further reduced to yield hydroxylamine as the only product detected using a rotating Au(ring)|Hm|Au(np)|GC (disk) electrode. Additional evidence in support of this series mechanism was obtained from numerical simulations in which the bifunctional electrode was regarded as a hexagonal, closed-packed array of coplanar concentric Cd|Au(np) disks and Hm|GC rings (with no insulating gap), using rate constants determined independently from rotating Au and Hm|GC disk electrodes in solutions containing either nitrate or nitrite, respectively.

Powering denitrification: the perspectives of electrocatalytic nitrate reduction

“…Such an approach has been dubbed "rational design of electrocatalytic interfaces" in a recent paper 128 . Au nanoparticles and hemin (Fe-protoporphyrin IX) were co-deposited on a GC disk electrode.…”

The Oxidation of Hydroxylamine on Gold Electrodes in Mildly Acidic Aqueous Electrolytes: Electrochemical and In Situ Differential Reflectance Studies

“…7 Although the activity of Hm for nitrite reduction either in the form of electropolymerized Hm films or layers of monomers mixed with didodecyldimethylammonium bromide ͑DDAB͒ has been well documented, 8 the present study appears to be the first involving a simple Hm monolayer spontaneously adsorbed on a carbonaceous surface for studies of this specific reaction. As will be shown, Hm|GC is inactive toward reduction of both HAM and nitrate 6 and, therefore, affords a highly specific means for monitoring solution phase nitrite without interference from those species.…”

“…As has been well established, 7 Cd underpotential deposition, Cd͑UPD͒, on Au promotes reduction of nitrate and nitrite in aqueous acidic electrolytes. This effect is illustrated in Fig.…”

Efecto electrocatalítico de nanopartículas bimetálicas de Ag y Cd hacia la reducción de iones nitrato y/o nitrito

“…Sin embargo, estas técnicas generalmente requieren tratamientos posteriores de los efluentes que no pueden ser adaptados fácilmente a contenidos de iones nitrato variables o condiciones de flujo de agua. Por eso, la estrategia general basada en la reducción de iones nitratos por métodos electroquí-micos recibieron considerable atención a través de las últimas tres décadas para remover este analito de muestras de aguas contaminadas [7]. Los productos de reacción (H 2 , NO 2 -, NH 3 , N 2 y otros óxidos nitrogenados) para este proceso de reducción resultan fuertemente dependientes del material del electrodo así como también del pH del medio [8].…”