Chemical and Electronic Effects of Ni in Pt/Ni and Pt/Ru/Ni Alloy Nanoparticles in Methanol Electrooxidation

Abstract

Electrooxidation of methanol in sulfuric acid solution was studied using Pt, Pt/Ni(1:1 and 3:1), Pt/Ru/Ni(5: 4:1 and 6:3.5:0.5), and Pt/Ru(1:1) alloy nanoparticle catalysts, in relation to methanol oxidation processes in the direct oxidation methanol fuel cell. The Pt/Ni and Pt/Ru/Ni alloys showed excellent catalytic activities compared to those of pure Pt and Pt/Ru. The role of Ni as a catalytically enhancing agent in the oxidation process was interrogated using cyclic voltammetry, chronoamperometry, X-ray photoelectron spectroscopy, transmission electron microscopy, and X-ray diffraction. X-ray diffraction data showed alloy formation for all Pt/Ni, Pt/Ru/Ni, and Pt/Ru nanoparticles, whereas X-ray photoelectron spectroscopy confirmed that chemical states of Pt were exclusively metallic. The presence of metallic Ni, NiO, Ni(OH) 2 , NiOOH, metallic Ru, RuO 2 , and RuO 3 was also confirmed. We found that the Pt4f binding energies for the Pt/Ni and Pt/Ru/Ni alloy nanoparticles were lower than those for clean Pt nanoparticles. The oxides that serve as the oxygen donors for the oxidation process, and the change in the electronic structure of the Pt component in the alloys versus those in Pt and Pt/Ru collectively account, we believe, for enhancement in rates of methanol oxidation. The difference in the peak shift in Pt4f between Pt/Ni and Pt/Ru alloy nanoparticles is discussed by using electronegativities of the three components: Pt, Ru, and Ni. A comparison between the alloy nanoparticle composition and that of disk alloy electrodes under similar conditions was made in terms of the surface-tovolume ratio and surface segregation of the alloying components.

Graphene-based transition metal oxide nanocomposites for the oxygen reduction reaction

“…Transition metal oxides have been intensively studied to be widely used in various fields. In addition to its well-known superiority, the other predominant characteristics of transition metal oxides for their groundbreaking application in the ORR should be highlighted: (1) abundant hydroxyl groups are inserted on the surfaces of transition metal oxides, which could be further functionalized by genetic materials (DNA and RNA) for biological catalysts; 11 (2) crystalline construction of transition metal oxides often have strong interactions, which could prevent the agglomeration of metal particles and maintain small metal particle sizes; 12,13 (3) they have considerably higher alkaline corrosion resistance in the electrochemical environment compared to noble metal and carbon-based materials due to the stabilization of the high oxidation state of transition metallic elements. In the past decade, due to excellent nanocomposite catalysts, novel advanced material-based transition metal oxides were created.…”

Development of plurimetallic electrocatalysts prepared by decomposition of polymeric precursors for EtOH/O2 fuel cell

“…9,25 In our opinion, the good matches between the patterns of the quaternary catalyst and pure Pt crystallites are due the opposite effects that Ru, Ni, and Sn have on the crystal structure. Displacement of the crystallographic planes, indicating alloy formation, have also been observed for some PtRuNi/C electrocatalysts prepared by Park, 10 Wang, 19 Liang, 21 and Moreno 32 via different synthetic routes. Taking into account the XRD pattern, one can infer that the preparation of nanocatalysts by DPP suggest Sn, Ru, and Ni incorporation into the Pt crystallite, with consequent alloy formation.…”

“…In addition, materials that have Ni in the presence of Ru and/or Sn have furnished promising results regarding the ethanol oxidation in DEFC. 10,[18][19][20][21] Camara et al 22 has conducted FTIR studies on PtRu and showed that the amount of acetic acid produced is related to the amount of Ru in the catalyst, i.e., the larger the amount of Ru in the electrocatalyst, the higher the formation of acetic acid and the lower the production of acetaldehyde during ethanol oxidation.…”

“…Nevertheless, it is well known that alloys including elements such as Sn, Ru, Ni, Co, Rh, Pd, and W, among others in the platinum structure are much more efficient materials in terms of ethanol oxidation at lower potentials (E < 0.4 V vs. RHE). [8][9][10][11] This outstanding characteristic is explained by two different effects, namely the bifunctional 12,13 and electronic or binder effects. [14][15][16] The bifunctional effect, first described by Watanabe and Motoo, 12,13 ocurrs when elements less noble than Pt and with high affinity for water molecules, such as Ru, easily form oxygen or hydrated oxides species next to a Pt site onto which the organic intermediate is adsorbed.…”

“…In addition, materials that have Ni in the presence of Ru and/or Sn have furnished promising results regarding the ethanol oxidation in DEFC. 10,[18][19][20][21] Camara et al 22 has conducted FTIR studies on PtRu and showed that the amount of acetic acid produced is related to the amount of Ru in the catalyst, i.e., the larger the amount of Ru in the electrocatalyst, the higher the formation of acetic acid and the lower the production of acetaldehyde during ethanol oxidation.Literature is controversial concerning the selectivity toward acetic acid and acetaldehyde formation during ethanol oxidation on PtSn/C and PtSnRu/C electrocatalysts. After 5 h of electrolysis, Simões et al 23 have observed formation of acetic acid, acetaldehyde, and CO 2 in the presence of PtSn electrocatalysts, as attended by HPLC and FTIR analysis.…”