Intermetallic Nanoarchitectures for Efficient Electrocatalysis

Highly Diluted Pt Atoms Modified RhBi Intermetallic Nanoplates Boost Ethanol Oxidation Electrocatalysis

Engineering Pt-based multimetallic nanoalloys could boost electrocatalysis in broad applications, yet it remains challenging in terms of its rational design and synthesis of a highly diluted alloy with unprecedented Pt atomic utilization. Herein, atomically dispersed Pt anchored on the surface of novel RhBi intermetallic nanoplates (RhBi-Pta) is achieved by atomic replacement, which transforms into a tensile-strained and highly diluted RhPta alloy (RhBi@RhPta) via electrochemical dealloying. Due to the diluted Pt atoms and tensile-strained Rh shell, the RhBi@RhPta electrocatalyst exhibits a remarkably enhanced peak mass activity of 32459.1 mA mg-1Pt toward the ethanol oxidation reaction (EOR) in alkaline electrolyte, while RhBi and RhBi-Pta intermetallic nanocrystals show negligible activities. This work provides a general strategy for engineering highly diluted alloys for highly efficient electrocatalysis, based on the well-defined intermetallic compounds.

Intermetallic Compound and Solid Solutions of Co75Me25 (Me: Si, Fe, Cr) as Catalysts for the Electrochemical Reaction of Nitrate Conversion to Ammonia

A sustainable reaction of electrocatalytic nitrate conversion in ammonia production (NO3RR) occurring under ambient conditions is currently of prime interest, as well as urgent research due to the real potential replacement of the environmentally unfavorable Haber-Bosch process. Herein, a series of electrocatalysts based on two-component cobalt alloys was synthesized using low-cost non-noble metals Co, Fe, Cr, and also Si. The samples of electrocatalysts were characterized and studied by the following methods: SEM, EDX, XRD (both transmission and reflection), UV-VIS spectroscopy, optical microscopy, linear (and cyclic) voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Beyond that, the determination of electrochemically active surface area was also carried out for all samples of electrocatalysts. Unexpectedly, the sample having an intermetallic compound (IMC) of the composition Co2Si turned out to be the most highly effective. The highest Faradaic efficiency (FE) of 80.8% at E = -0.585 V (RHE) and an ammonia yield rate of 22.3 µmol h-1 cm-2 at E = -0.685 V (RHE) indicate the progressive role of IMC as the main active component of the electrocatalyst. Thus, this study demonstrates the promise and enormous potential of IMC as the main component of highly efficient electrocatalysts for NO3RR. This work can serve primarily as a starting point for future studies of electrocatalytic conversion reactions in the production of ammonia using IMC catalysts containing non-noble metals.

Exploration of metal-free 2D electrocatalysts toward the oxygen electroreduction

The advancement of economical and readily available electrocatalysts for the oxygen reduction reaction (ORR) holds paramount importance in the advancement of fuel cells and metal-air batteries. Recently, 2D non-metallic materials have obtained substantial attention as viable alternatives for ORR catalysts due to their manifold advantages, encompassing low cost, ample availability, substantial surface-to-volume ratio, high conductivity, exceptional durability, and competitive activity. The augmented ORR performances observed in metal-free 2D materials typically arise from heteroatom doping, defects, or the formation of heterostructures. Here, the authors delve into the realm of electrocatalysts for the ORR, pivoting around metal-free 2D materials. Initially, the merits of metal-free 2D materials are explored and the reaction mechanism of the ORR is dissected. Subsequently, a comprehensive survey of diverse metal-free 2D materials is presented, tracing their evolutionary journey from fundamental concepts to pragmatic applications in the context of ORR. Substantial importance is given on the exploration of various strategies for enhancing metal-free 2D materials and assessing their impact on inherent material performance, including electronic properties. Finally, the challenges and future prospects that lie ahead for metal-free 2D materials are underscored, as they aspire to serve as efficient ORR electrocatalysts.

Symmetry-Induced Regulation of Pt Strain Derived from Pt3 Ga Intermetallic for Boosting Oxygen Reduction Reaction

Pt-based fuel cell catalysts with excellent activity and stability for proton-exchange membrane fuel cells (PEMFCs) have been developed through strain regulation in recent years. Herein, this work demonstrates that symmetry-induced strain regulation of Pt surface of PtGa intermetallic compounds can greatly enhance the catalytic performance of the oxygen reduction reaction (ORR). With the strain environment varies derived from the lattice mismatch of analogous PtGa core but different symmetry, the Pt surface of the PtGa alloy and the Pt3 Ga (Pm3 ¯ $\bar{3}$ m) precisely realize 0.58% and 2.7% compressive strain compared to the Pt3 Ga (P4/mmm). Experimental and theoretical results reveal that when the compressive stress of the Pt lattice increases, the desorption process of O* intermediates becomes accelerated, which is conducive to oxygen reduction. The Pt3 Ga (Pm3 ¯ $\bar{3}$ m) with high symmetry and compressive Pt surface exhibit the highest mass and specific activities of 2.18 A mgPt -1 and 5.36 mA cm-2 , respectively, which are more than one order of magnitude higher than those of commercial Pt/C catalysts. This work demonstrates that material symmetry can be used to precisely modulate Pt surface stress to enhance the ORR, as well as provide a distinct platform to investigate the relationship between Pt compressibility and catalytic activity.

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.