Towards the Effect of Pt⁰/Pt^δ+ and Ce³⁺ Species at the Surface of CeO₂ Crystals: Understanding the Nature of the Interactions under CO Oxidation Conditions

Abstract

We synthesized CeO2 nanowires and nanocubes showing {110}+{100} and {100} surfaces predominantly, respectively, once the different surface energies play a crucial role in the behavior of Ce4+/Ce3+ reversibility. We found out that Pt/CeO2 nanowires presented more Ce3+ content, oxygen vacancies, and atomically dispersed Pt, indicating a stronger Pt−Ce interaction. In contrast, the Pt/CeO2 nanocubes presented a higher contribution of Ptδ+ species, suggesting a well‐controlled Pt particle size (∼1 nm) and significant interaction with ceria, with oxygen species more available at the surface. Thus, we suggest that the ceria‘s different surface energies may lead to different Pt distributions of species over the supports. H2‐reduction treatment led to changes in Pt structure that showed a better catalysis performance for the Pt/CeO2 nanowires essentially, supported by XPS and CO‐DRIFTS. Nevertheless, this step did not cause improved activity to the point of overcoming the nanocubes‐based catalyst, and the reasons were fully discussed. Herein, we propose that catalysts′ performance depends on a complex combination of several materials′ characteristics. These features may lead to different reaction pathways depending on the pre‐treatment of the samples.

MnO2-Ir Nanowires: Combining Ultrasmall Nanoparticle Sizes, O-Vacancies, and Low Noble-Metal Loading with Improved Activities towards the Oxygen Reduction Reaction

“…Due to metal-support interactions, the deposition of noble metals over MnO 2 has been an efficient strategy for improving electrocatalytic performances [ 21 , 22 ]. Moreover, metal NPs may interact/cooperate with metal oxides to facilitate catalytic reactions, in which the reducibility of the inorganic matrix usually represents a key element over the detected catalytic activities [ 23 , 24 ]. To further provide in-depth information into these features, the ultrasmall Ir NPs decorated onto MnO 2 nanowires by hydrogen temperature-programmed reduction was investigated, as shown in Figure 3 B.…”

“…Before the H 2 -TPR measurements, the samples were heat-treated at 200 °C for 30 min under N 2 flow to remove moisture adsorbed. After cooling to room temperature, the reduction gas of 8.0% H 2 /N 2 at a flow rate of 20 mL/min was introduced, and the temperature was raised linearly to 950 °C at a heating rate of 10 [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ] Using Spectro Arcos equipment, the Ir atomic percentages were measured by inductively coupled plasma optical emission spectrometry (ICP-OES). For ICP-OES, the MnO 2 powder samples were fixed on stainless steel holders using double adhesive carbon tape.…”

Application of AgPt Nanoshells in Direct Methanol Fuel Cells: Experimental and Theoretical Insights of Design Electrocatalysts over Methanol Crossover Effect

“…[52] The same was carried out for evaluating Pt species, and the high-resolution spectrum (Figure 3B) showed Pt 0 (4f 7/2 = 71.3 eV; 4f 5/2 = 74.7 eV) and Pt 2 + (4f 7/2 = 72.4 eV; 4f 5/2 = 75.6 eV) species. [11] The XPS data allowed us to calculate that the catalyst presents on its surface 60.5 % of Ag 0 and 39.5 % of Ag + and 55.1 % of Pt 0 and 44.9 % of Pt + 2 .…”

“…Materials possessing well-controlled shape, size, composition, and structure (hollow vs. solid interiors) present unique opportunities for catalysis. [8][9][10][11] These features led to the rise of a revolution in the field, which encompasses an excellent possibility for active ORR cathodes' development. Yet, unlike pure Pt-based electrocatalysts, alloys comprised of Pt and a second metal (noble or not) can be very selective, diminishing the methanol crossover effect.…”

“…Materials possessing well‐controlled shape, size, composition, and structure (hollow vs. solid interiors) present unique opportunities for catalysis [8–11] . These features led to the rise of a revolution in the field, which encompasses an excellent possibility for active ORR cathodes′ development.…”