Design of a Pd–Au Nitrite Reduction Catalyst by Identifying and Optimizing Active Ensembles

Abstract

Nitrate (NO 3 − ) is a ubiquitous contaminant in groundwater that causes serious public health issues around the world. Though various strategies are able to reduce NO 3 − to nitrite (NO 2 − ), a rational catalyst design strategy for NO 2 − removal has not been found, in part because of the complicated reaction network of nitrate chemistry. In this study, we show, through catalytic modeling with density functional theory (DFT) calculations, that the performance of mono-and bimetallic surfaces for nitrite reduction can be rapidly screened using N, N 2 , and NH 3 binding energies as reactivity descriptors.With a number of active surface atomic ensembles identified for nitrite reduction, we have designed a series of "metal-on-metal" bimetallics with optimized surface reactivity and a maximum number of active sites. Choosing Pd-on-Au nanoparticles (NPs) as candidate catalysts, both theory and experiment find that a thin monolayer of Pd-on-Au NPs (size: ∼4 nm) leads to high nitrite reduction performance, outperforming pure Pd NPs and the other Pd surface compositions considered. Experiments show that this thin layer of Pd-on-Au has a relatively high selectivity for N 2 formation, compared to pure Pd NPs. More importantly, our study shows that a simple model, based upon DFTcalculated thermodynamic energies, can facilitate catalysts design relevant to environmental issues.

Identification and elimination of false positives in electrochemical nitrogen reduction studies

“…More importantly, electrodes, electrocatalysts, electrolytes, solvents and any other component of the experimental setup that is nitrogenbased or was prepared using N-containing precursor(s) can be a source of contamination. In this scenario, ammonia can be either released spontaneously upon bringing different components into [27][28][29][30][54][55][56][57] of some of the known electrocatalysts for each process.…”

“…Upon reaching this highly unfortunate outcome, we considered a range of possibilities that could result in false-positive NRR results by scrutinising the experimental procedures described in the relevant papers. The common feature of all these studies was the lack of any reasonable control, or quantification, of the NO x contamination, notwithstanding the fact that bismuth and gold are known to efficiently catalyse the NO x electroreduction to ammonia [27][28][29][30] . A range of tests in our laboratories with both ionic and gaseous NO x compounds indeed confirmed that Bi and Au/C can produce NH 3 quite efficiently with the rates of the order of 0.1-1.0 nmol s −1 cm −2 when these contaminants are present ( Fig.…”

Microstructure Optimization of Mos2/Sepiolite Nanocomposites via a Surfactant-Assisted Hydrothermal Strategy for High Efficiency Photocatalysis

“…In fact, the surfactant-assisted synthesis of MoS 2 has the advantages of low cost, easy operation, and excellent performance, and some surfactants are utilized to optimize MoS 2 -based nanocomposite [11][12][13][14][15]. Sepiolite is a typical clay mineral with the features of environmentfriendly and low cost, which makes it a good carrier for catalyst because the large surface specific area and excellent adsorption are benefit for the high catalytic performance [16][17][18][19]. However, surfactant (cationic, anionic, and nonionic surfactant) with different charges will affect both catalyst and carrier, due to the surface charge of sepiolite [20,21].…”

Synthesis, Characterization and Antifungal Activity of Fe(III) Metal–Organic Framework and its Nano-composite

“…Also, the incorporation of Ag-Ir NPs in the pores of Co 3 O 4 leads to about 56% enhancement in selectivity. The performance of bimetallic and single metal surfaces for the reduction of nitrite has been shown to be rapidly enhanced using binding energies of ammonia (NH 3 ), nitrogen (N), and nitrogen gas (N 2 ) to describe the reactivity through catalyst modeling using the density functional theory (DFT) calculations [26][27][28].…”