Ordered Mesoporous Carbon Confined Highly Dispersed PtCo Alloy for the Oxygen Reduction Reaction: The Effect of Structure and Composition on Performance

Boosting Bifunctional Catalysis by Integrating Active Faceted Intermetallic Nanocrystals and Strained Pt-Ir Functional Shells

PtIr-based nanostructures are fascinating materials for application in bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysis. However, the fabrication of PtIr nanocatalysts with clear geometric features and structural configurations, which are crucial for enhancing the bifunctionality, remains challenging. Herein, PtCo@PtIr nanoparticles are precisely designed and fabricated with a quasi-octahedral PtCo nanocrystal as a highly atomically ordered core and an ultrathin PtIr atomic layer as a compressively strained shell. Owing to their geometric and core-shell features, the PtCo@PtIr nanoparticles deliver approximately six and eight times higher mass and specific activities, respectively, as an ORR catalyst than a commercial Pt/C catalyst. The half-wave potential of PtCo@PtIr exhibits a negligible decrease by 9 mV after 10 000 cycles, indicating extraordinary ORR durability because of the ordered arrangement of Pt and Co atoms. When evaluated using the ORR-OER dual reaction upon the introduction of Ir, PtCo@PtIr exhibits a small ORR-OER overpotential gap of 679 mV, demonstrating its great potential as a bifunctional electrocatalyst for fabricating fuel cells. The findings pave the way for designing precise intermetallic core-shell nanocrystals as highly functional catalysts.

Two-stage confinement derived small-sized highly ordered L10-PtCoZn for effective oxygen reduction catalysis in PEM fuel cells

Intermetallic ordered PtCo is effective for high oxygen reduction reaction (ORR) activity and stability. However, preparing small-sized, highly ordered PtM alloys is still challenging. Herein, we report a controlled two-stage confinement strategy, in which highly ordered PtCoZn/NC nanoparticles of 5.3 nm size were prepared in a scalable process. The contradiction between the high ordering degree with the small particle size as well as the atomic migration with the space confinement was well resolved. An outstanding PEMFC performance was achieved for L10-PtCoZn/NC with a high mass activity (MA) of 1.21 A/mgPt at 0.9 ViR-free, 80.1 % MA retention after 30 k cycles in H2-O2 operation, and a high mass-specific power density of 8.24 W mg-1Pt in H2-Air operation with a slight loss of cell voltage@0.8 A cm-2 of 28 mV after 30 k cycles. The high performance can be ascribed to the high Pt area exposure, the enhanced Pt-Co coupling, and the prevented agglomeration in the mesoporous carbon wall. Overall, this strategy may contribute to the commercialization of fuel cells.

Intermetallic Nanocrystals for Fuel-Cells-Based Electrocatalysis

Electrocatalysis underpins the renewable electrochemical conversions for sustainability, which further replies on metallic nanocrystals as vital electrocatalysts. Intermetallic nanocrystals have been known to show distinct properties compared to their disordered counterparts, and been long explored for functional improvements. Tremendous progresses have been made in the past few years, with notable trend of more precise engineering down to an atomic level and the investigation transferring into more practical membrane electrode assembly (MEA), which motivates this timely review. After addressing the basic thermodynamic and kinetic fundamentals, we discuss classic and latest synthetic strategies that enable not only the formation of intermetallic phase but also the rational control of other catalysis-determinant structural parameters, such as size and morphology. We also demonstrate the emerging intermetallic nanomaterials for potentially further advancement in energy electrocatalysis. Then, we discuss the state-of-the-art characterizations and representative intermetallic electrocatalysts with emphasis on oxygen reduction reaction evaluated in a MEA setup. We summarize this review by laying out existing challenges and offering perspective on future research directions toward practicing intermetallic electrocatalysts for energy conversions.

Recent Progress in Using Mesoporous Carbon Materials as Catalyst Support for Proton Exchange Membrane Fuel Cells

Developing durable oxygen reduction reaction (ORR) electrocatalysts is essential to step up the large-scale applications of proton exchange membrane fuel cells (PEMFCs). Traditional ORR electrocatalysts provide satisfactory activity, yet their poor durability limits the long-term applications of PEMFCs. Porous carbon used as catalyst support in Pt/C is vulnerable to oxidation under high potential conditions, leading to Pt nanoparticle dissolution and carbon corrosion. Thus, integrating Pt nanoparticles into highly graphitic mesoporous carbons could provide long-term stability. This Perspective seeks to reframe the existing approaches to employing Pt alloys and mesoporous carbon-integrated ORR electrocatalysts to improve the activity and stability of PEMFCs. The unusual porous structure of mesoporous carbons promotes oxygen transport, and graphitization provides balanced stability. Furthermore, the synergistic effect between Pt alloys and heteroatom doping in mesoporous carbons not only provides a great anchoring surface for catalyst nanoparticles but also improves the intrinsic activity. Furthermore, the addition of Pt alloys into mesoporous carbon optimizes the available surface area and creates an effective electron transfer channel, reducing the mass transport resistance. The long-term goals for fuel-cell-powered cars, especially those designed for heavy-duty use, are well aligned with the results shown when this hybrid material is used in PEMFCs to improve performance and durability.

Electrochemical Activation and Its Prolonged Effect on the Durability of Bimetallic Pt-Based Electrocatalysts for PEMFCs

The present study, concerned with high-performance ORR catalysts, may be a valuable resource for a wide range of researchers within the fields of nanomaterials, electrocatalysis, and hydrogen energy. The objects of the research are electrocatalysts based on platinum–copper nanoparticles with onion-like and solid-solution structures. To evaluate the functional characteristics of the catalysts, the XRD, XRF, TEM, HAADF-STEM, and EDX methods, as well as the voltammetry method on a rotating disk electrode have been used. This work draws the attention of researchers to the significance of applying a protocol of electrochemically activating bimetallic catalysts in terms of the study of their functional characteristics on the rotating disk electrode. The choice of the potential range during the pre-cycling stage has been shown to play a crucial role in maintaining the durability of the catalysts. The activation of the PtCu/C catalyst during cycling of up to 1.0 V allows for an increase in the durability of the catalysts with onion-like and solid-solution structures of nanoparticles by 28% and 23%, respectively, as compared with activation of up to 1.2 V.