Ti/Pt−Pd‐Based Nanocomposite: Effects of Metal Oxides on the Oxygen Reduction Reaction

Abstract

Over the last few years, there has been an intensive search for stable and highly active electrocatalysts, which are intended to be applied in oxygen reduction reaction (ORR) preferably without the use of noble metals or with the application of a very small quantity of these metals in the process. Electrocatalysts that satisfy these conditions can be composed of Ti and other metals, supported or not by carbonaceous materials. The present work reports the application of synthesized threedimensional Ti/PtÀ Pd nanoparticles with highly rough surfaces supported on graphene nanoribbons (Ti/PtÀ Pd/GNR nanocomposite) by a single one-pot reaction, and applied in ORR. Unlike the effect of strong metal-support interaction (SMSI), which favors electrons transfer from the metal support to the catalyst, the mechanism employed in this study favored the transfer of electrons from the catalyst to the metal support; in other words, the mechanism led to the oxidation of Pt and Pd. Pt, which exhibited PtÀ Pd type alloy features, was found to be more externally distributed at the rough surface of the metallic structures. Additionally, Ti, which presented oxide features, was found to be even more externally distributed at the surface of PtÀ Pd on non-electrochemically and electrochemically stabilized Ti/PtÀ Pd/GNR nanocomposite electrodes. Since all these metals have great amounts of different oxides (i. e. are highly oxidized), the oxides are found to be energetically responsible for the improvement in ORR electrocatalytic activity and stability of Ti/PtÀ Pd/GNR/GC electrodes in comparison with the ORR responses for PtC TKK/GC and PtÀ Pd/GNR/GC modified electrodes. To Ti-containing catalysts, the high activity is attributable to enhancing the intrinsic activity and the high selectivity to 4-electron ORR is due to the fact that presence of Ti contributes to oxygen-binding energy of these nanocomposites shifts toward more positive values (weakening oxygen bonding).[a] G.

Synthesis of Free‐Standing Alloyed PdSn Nanoparticles with Enhanced Catalytic Performance for Ethanol Electrooxidation

“…When the fresh Pd x Sn y NPs catalysts are put in the solution, ethanol molecules (eq 1) and OH − ions would absorb on the surface of Pd, followed by the formation of *C 2 H 5 OH and *OH, respectively. During forward scanning, *C 2 H 5 OH would be oxidated to *CH 3 CO (*CH 3 CHOH→*CH 3 CHO→*CH 3 CO) with the help of *OH through three electrons step by step (eq 2) at the potential between −0.90 and −0.45 V. Afterwards, *CH 3 CO and *OH would react to from *CH 3 COOH (eq 3) at the potential between −0.45 and 0.00 V, where the rate determination step occurs, corresponding to the on‐set potential of CVs [35] . Meanwhile, lots of fresh Pd atoms expose again (eq 4), leading to the increase of catalytic current density.…”

“…*CH 3 CO) with the help of *OH through three electrons step by step (eq 2) at the potential between À 0.90 and À 0.45 V. Afterwards, *CH 3 CO and *OH would react to from *CH 3 COOH (eq 3) at the potential between À 0.45 and 0.00 V, where the rate determination step occurs, corresponding to the on-set potential of CVs. [35] Meanwhile, lots of fresh Pd atoms expose again (eq 4), leading to the increase of catalytic current density. When most of fresh Pd are exposal, the peak current density is denoted as jf.…”

Proton Exchange Membrane Fuel Cells (PEMFCs): Advances and Challenges

“…Another strategy to increase the support stability is by incorporating metal oxide as catalyst supports. For this reason, a wide variety of options for novel Pt supported with metal oxides, such as NbOx [ 236 ], In 2 O 3 [ 237 ] , and TiO 2 [ 238 ] , have been explored. However, those kinds of metal oxide materials have poor conductivity, which makes it necessary to develop different strategies to increase conductivity, such as: Adding carbon-based materials like CNT [ 232 ], C [ 236 ], or graphene nanoribbons [ 238 ]; Alloying of Pt with other metals, such as In [ 237 ]; Incorporating some nitride compounds, such as TiN [ 239 ].…”

“…Another strategy to increase the support stability is by incorporating metal oxide as catalyst supports. For this reason, a wide variety of options for novel Pt supported with metal oxides, such as NbOx [236], In 2 O 3 [237] , and TiO 2 [238] , have been explored. However, those kinds of metal oxide materials have poor conductivity, which makes it necessary to develop different strategies to increase conductivity, such as:…”

“…Adding carbon-based materials like CNT [232], C [236], or graphene nanoribbons [238]; • Alloying of Pt with other metals, such as In [237]; • Incorporating some nitride compounds, such as TiN [239].…”