Leveraging Commercial Silver Inks as Oxidation Reduction Reaction Catalysts in Alkaline Medium

Alkaline exchange membrane fuel cells (AEMFCs) development is impeded by the lack of low-cost processes for fabricating catalyst layers. One bottleneck lies in using large amounts of precious group metals during the layer deposition process by spray-painting. One possible solution would be to leverage inkjet printing technologies known for their full recovery of the printed material. Recent advances in printed electronics has led to the commercialization of silver (Ag) inks. We demonstrate the electrocatalytic properties (oxygen reduction reaction (ORR)) of Ag ink. Moreover, we show that a simple galvanic replacement reaction (GRR) on the Ag ink yields Ag_0.9M_0.1 (M = Pt or Pd) hollow nanoparticles. The resultant electrocatalyst demonstrated high activity for the ORR in alkaline medium. The Ag colloidal dispersion (the ink) reacted with a minute amount of platinum group metals precursors (PGMs). X-ray diffraction (XRD) and electron microscopy confirmed the hollow morphology and the formation of Pt or Pd-rich surfaces. The onset voltage for alkaline ORR activities follows the trend Ag_0.9Pt_0.1 > Ag_0.9Pd_0.1 > Ag. These experiments are a first step toward inkjet printing usage for fabricating catalytic layers

Morphological, Structural, and Compositional Evolution of Pt–Ni Octahedral Electrocatalysts with Pt‐Rich Edges and Ni‐Rich Core: Toward the Rational Design of Electrocatalysts for the Oxygen Reduction Reaction

The progress in colloidal synthesis of Pt–Ni octahedra has been instrumental in rising the oxygen reduction reaction catalytic activity high above the benchmark of Pt catalysts. This impressive catalytic performance is believed to result from the exposure of the most active catalytic sites after an activation process, chemical or electrochemical, which leads to a Pt surface enrichment. A foremost importance is to understand the structure and the elemental distribution of Pt–Ni octahedral, which leads to an optimal catalytic activity and stability. However, the factors governing the synthesis of the Pt–Ni octahedra are not well understood. In this study, unprecedented surface atomic segregation of Pt atoms in a Ni‐rich Pt–Ni octahedral nanoparticle structure is established by advanced electron microscopy. The Pt atoms are almost exclusively located on the edges of the Pt–Ni octahedra. This structure is formed in a pristine form, i.e., prior to any chemical or electrochemical etching. A new growth mechanism is revealed, which involves the transformation from an octahedron with a Pt‐rich core to a Ni‐rich octahedron with Pt‐rich edges. This observation may pave the way for a deeper understanding of this class of Pt–Ni octahedral nanoparticles as an electrocatalyst

Size dependent oxygen reduction and methanol oxidation reactions: catalytic activities of PtCu octahedral nanocrystals

The synthetic control through colloidal synthesis led to a remarkable increase in platinum mass activity in octahedral nanocrystals with a Pt-rich surface. In this manuscript, we demonstrate that the ratio of surfactant can tune the size of Pt surface enriched PtCu nano-octahedra from 8 to 18 nm with homogeneous size and shape on the carbon support. For the nano-octahedra, the Pt-rich surface has been determined by high-angle annular dark field scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy. The Pt-rich surface exhibits an increasing compressive strain with increasing surface of the {111} facets. With increasing surface, the PtCu nano-octahedra display higher oxygen reduction reaction (ORR) activity, which however leads to higher onset over-potentials in the methanol oxidation reaction (MOR) and CO-stripping. This observed trend for a series of size-selected nano-octahedra demonstrates the benefits of controlling the strained {111} Pt surface for the ORR and MOR activity

An Engineered Nanocomplex with Photodynamic and Photothermal Synergistic Properties for Cancer Treatment

Photodynamic therapy (PDT) and photothermal therapy (PTT) are promising therapeutic methods for cancer treatment; however, as single modality therapies, either PDT or PTT is still limited in its success rate. A dual application of both PDT and PTT, in a combined protocol, has gained immense interest. In this study, gold nanoparticles (AuNPs) were conjugated with a PDT agent, meso-tetrahydroxyphenylchlorin (mTHPC) photosensitizer, designed as nanotherapeutic agents that can activate a dual photodynamic/photothermal therapy in SH-SY5Y human neuroblastoma cells. The AuNP-mTHPC complex is biocompatible, soluble, and photostable. PDT efficiency is high because of immediate reactive oxygen species (ROS) production upon mTHPC activation by the 650-nm laser, which decreased mitochondrial membrane potential (∆ψm). Likewise, the AuNP-mTHPC complex is used as a photoabsorbing (PTA) agent for PTT, due to efficient plasmon absorption and excellent photothermal conversion characteristics of AuNPs under laser irradiation at 532 nm. Under the laser irradiation of a PDT/PTT combination, a twofold phototoxicity outcome follows, compared to PDT-only or PTT-only treatment. This indicates that PDT and PTT have synergistic effects together as a combined therapeutic method. Our study aimed at applying the AuNP-mTHPC approach as a potential treatment of cancer in the biomedical field

Highly Active and Stable Large Mo-Doped Pt–Ni Octahedral Catalysts for ORR: Synthesis, Post-treatments, and Electrochemical Performance and Stability

International audienc

On the electrocatalytical oxygen reduction reaction activity and stability of quaternary RhMo-doped PtNi/C octahedral nanocrystals

Recently proposed bimetallic octahedral Pt–Ni electrocatalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cell (PEMFC) cathodes suffer from particle instabilities in the form of Ni corrosion and shape degradation. Advanced trimetallic Pt-based electrocatalysts have contributed to their catalytic performance and stability. In this work, we propose and analyse a novel quaternary octahedral (oh-)Pt nanoalloy concept with two distinct metals serving as stabilizing surface dopants. An efficient solvothermal one-pot strategy was developed for the preparation of shape-controlled oh-PtNi catalysts doped with Rh and Mo in its surface. The as-prepared quaternary octahedral PtNi(RhMo) catalysts showed exceptionally high ORR performance accompanied by improved activity and shape integrity after stability tests compared to previously reported bi- and tri-metallic systems. Synthesis, performance characteristics and degradation behaviour are investigated targeting deeper understanding for catalyst system improvement strategies. A number of different operando and on-line analysis techniques were employed to monitor the structural and elemental evolution, including identical location scanning transmission electron microscopy and energy dispersive X-ray analysis (IL-STEM-EDX), operando wide angle X-ray spectroscopy (WAXS), and on-line scanning flow cell inductively coupled plasma mass spectrometry (SFC-ICP-MS). Our studies show that doping PtNi octahedral catalysts with small amounts of Rh and Mo suppresses detrimental Pt diffusion and thus offers an attractive new family of shaped Pt alloy catalysts for deployment in PEMFC cathode layers

Temperature-Driven Dissolution of Nanoalloyed Catalyst During Ink Preparation and Membrane Electrode Assembly Fabrication

Platinum (Pt) alloys are excellent oxygen-reduction catalysts used in proton exchange membrane fuel cells, yet their effective integration poses challenges. Through in-situ X-ray diffraction, we investigate the compositional changes during the ink preparation of PtCo and PtNi catalysts and reveal that dissolution is primarily driven by temperature. Comparisons with conventional catalyst-coated membrane (CCM) fabrication methods highlight structural transformations during hot-pressing. Paving the way for advancements in sustainable energy technologies, our findings emphasize the essential need for fundamental knowledge of ink-making and CCM fabrication to unlock Pt-alloy catalyst potential for hydrogen fuel cells. In addition to the academic community, the industry shall benefit from this precise and easy-to-employ methodology