Promotion Effects of Sn on the Electrocatalytic Reduction of Nitrate at Rh Nanoparticles

Abstract

We present a comparative study of the activity and selectivity of Rh/C nanoparticles and Sn‐modified Rh/C nanoparticles towards electrocatalytic nitrate reduction in sulfuric acid. Electrochemical techniques, combined with more direct analytical techniques such as mass spectrometry and ion chromatography, were applied to analyse the products obtained during the reaction. Online electrochemical mass spectrometry was employed to detect volatile products, such as nitric oxide (NO), nitrous oxide (N2O) and dinitrogen (N2). The combination of online sample collection to the electrochemical cell and offline ion chromatography allows the quantitative analysis of non‐volatile products, such as ammonium (${{\rm{NH}}_{\rm{4}}^ + }$) and hydroxylamine (NH3OH+). Non‐volatile products can be detected during nitrate reduction at Rh/C electrodes. The catalytic activity of Rh/C electrodes can be enhanced by Sn modification. N2O is the dominant volatile product at SnRh/C electrodes. ${{\rm{NH}}_{\rm{4}}^ + }$ is the main ionic product at the Rh/C electrodes, whereas modification by Sn also leads to the formation of NH3OH+.

Electrocatalytic Reduction of Nitrate on Tin-modified Palladium Electrodes

“…When both AuPd electrodes are modified with Sn, on both electrodes N 2 O is formed as the dominant volatile product and NH 2 OH as the dominant nonvolatile product. This is similar to the product distribution of the nitrate reduction on the Sn-modified bulk Pd electrode.This product spectrum is similar to the Sn modified platinum [6,24,25], whereas a Sn-modified rhodium electrode produces more ammonia [45], owing to the higher propensity of Rh to break the N-O bond.…”

“…The fragmentation ratio between N 2 O (m/z = 44) and NO (m/z = 30) was found to be 0.202 while between N 2 O and N 2 (m/z = 28) it was 0.0685 [24]. A SEM voltage of 1500 V was used for all species (m/z = 2, 14,15,28,30,31,33,44,45,46). Unfortunately it is not straightforward to deduce quantitative information in terms of faradaic efficiencies for the reaction products from OLEMS measurements.…”

Cathodic Arc-plasma Deposition of Platinum Nanoparticles on Fluorine-doped Tin Oxide for Electrocatalytic Nitrate Reduction Reaction

“…Fundamental studies on nitrate reduction electrocatalysts have focused on noble metal electrodes such as Pt and Pd. 1,3,4 Their catalytic activity has been drastically enhanced by the surface modification with p-block metal adatoms including Sn, [5][6][7][8][9][10][11][12][13] in which the interfaces between the noble metal substrate and the p-block metal adatoms may work as the catalytic active sites. To produce such interfaces, noble metal substrates have been widely used and modified with p-block elements even though the deposition of noble metal nanoparticles on conductive materials containing p-block elements can, in principle, give similar interfaces.…”

Octahedral Ni-nanocluster (Ni85) for Efficient and Selective Reduction of Nitric Oxide (NO) to Nitrogen (N2)

“…Therefore, the removal of NO is highly sought after and a major challenge for researchers. Extensive progress has been made over Pt 6 7 8 9 10 11 12 , Pd 13 14 15 , Rh 16 17 18 19 20 and Ir 21 22 23 metal surfaces for the catalytic conversion of NO to N 2 . However, the N-O bond dissociation is one of the most important steps and N-O can be dissociated via two pathways (i) direct N-O bond dissociation or (ii) indirect (hydrogenation followed by N-O bond dissociation).…”

“…However, the N-O bond dissociation is one of the most important steps and N-O can be dissociated via two pathways (i) direct N-O bond dissociation or (ii) indirect (hydrogenation followed by N-O bond dissociation). Earlier studies 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 reported that direct N-O bond dissociation is not thermodynamically favourable over Pt 6 7 8 9 10 11 12 , Pd 13 14 15 , Rh 16 17 18 19 20 and Ir 21 22 23 metal surfaces, but possible from their hydrogenated products (NOH, HNO, HNOH, H 2 NO), which increases the possibility of unwanted by-products. Therefore, the relative selectivity of N 2 vs. other products (N 2 O and NH 3 ) varies from catalyst to catalyst.…”