Platinum Catalysts Prepared with Functional Carbon Nanotube Defects and Its Improved Catalytic Performance for Methanol Oxidation

Abstract

Carbon nanotube (CNT) supported Pt nanoparticle catalysts have been prepared by spontaneous reduction of PtCl6(2-) ion as a result of direct redox reactions between PtCl6(2-) and oxygen-containing functional groups at defect sites of CNTs, which were introduced by chemical and electrochemical oxidation treatment of CNTs. The electrocatalytic properties of as-prepared Pt-CNT catalysts for methanol oxidation were investigated by chronopotentiometry and cyclic voltammetry. Compared with Pt catalysts prepared by hydrogen reduction and electrochemical deposition methods, Pt catalysts synthesized by functional CNT defects show excellent antipoisoning ability and long-term cycle stability.

Electrosynthesized Ni-Al Layered Double Hydroxide-Pt Nanoparticles as an Inorganic Nanocomposite and Potentate Anodic Material for Methanol Electrooxidation in Alkaline Media

“…This result approves that the PtNPs/Ni-Al LDH/GCE has a better electrocatalytic activity for methanol oxidation in alkaline media. The possible reason for this trend can be summarized as follows: (1) synergistic effect between PtNPs and Ni-Al LDH and its promoting properties; (2) content increase of metallic state of the PtNPs in the PtNPs/Ni-Al LDH/GCE nanocomposite, which is well known that the more content of metallic state in catalysts, the better catalytic performance; (3) increasing the conductivity of the PtNPs/Ni-Al LDH nanocomposite with respect to undopted Ni-Al LDH; and finally (4) as a hydroxide ion conductor, Ni-Al LDH could deliver OH -and increase the concentration of OH -around the PtNPs and bifunctional effect between the OH -and PtNPs similar with the commonly accepted bifunctional effect between Pt and Ru [57,58] in the case of Pt-Ru electrocatalyst [59] to remove the intermediate carbonaceous species and contribute to the low poisoning.…”

“…A linear relationship can be obtained between Ef and ln (v), as shown in the inset of Figure 6 (B). This indicates that the oxidation of methanol oxidation on the PtNPs/Ni-Al LDH/GCE electrocatalyst is completely an irreversible process [8,58].…”

“…The relation between the peak current density obtained from forward scan and v 1/2 is shown in Figure 6 (B). There is a linear relationship with a high correlation coefficient (R 2 >0.97) between peak current density and square root of scan rate, implying that the methanol oxidation is typically under diffusion control [57][58][59][60]. Moreover, Figure 7.…”

“…It can be seen that with an increase in OH − concentration the peak potential shifts toward more negative values and the anodic peak current density of methanol oxidation increase by increasing the NaOH concentration up to 0.3 M and then decrease at concentration higher than 0.3 M. These results indicate that the OH − ion participates in the oxidation of methanol and may be adverse to the oxidation of methanol for the competitive adsorption on the active sites to methanol. At low OH − concentration (<0.3 M), the peak potential shifts toward more negative values with an increase in OH − concentration, because as mentioned already the anodic current density in forward scan mainly comes from the oxidation of methanol and increasing the concentration of OH -around the PtNPs increase the bifunctional effect between the OH -and PtNPs [57][58][59] to remove the intermediate carbonaceous species and contribute to the low poisoning. On the other hand, in more alkaline electrolytes (>>0.3 M) the adsorption of OH -prevents the methanol adsorption on the electrocatalyst sites and so the reaction rate of methanol oxidation decreases [63].…”

PtCo alloy nanoparticles supported on graphene nanosheets with high performance for methanol oxidation

“…Thus the potential must increase to satisfy the applied current until a potential is reached where larger amounts of H 2 O can be decomposed [58]. The time at which the electrode potential jumps to a higher potential can be used to judge the antipoisoning ability of catalysts [59]. Obviously, the sustained time for these catalysts decreases in the order PtCo/G (~120 s)>Pt/G (~20 s)>PtCo/MWNTs (~10 s), consistenting with the I F /I R values based on CV tests.…”