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Abstract For global deployment of proton exchange membrane fuel cells, achieving optimal interaction between the components of the cathode active layer remains challenging. Studies addressing the effect of nanoparticle location (inside vs outside of pores) on performance and durability mostly compare porous and nonporous carbon supports, thus coming short of decoupling nanoparticle locality from carbon support effects. To address the influence of nanoparticle locality on performance and durability, new carbon‐supported electrocatalysts with designed and distinct nanoparticle localities are presented. The developed methodology allows to place Pt nanoparticles preferentially inside or outside of the mesopores of conductive carbon supports from materials under development at Cabot Corporation. Synthesis protocols are tuned to control nanoparticle size, crystallinity, and loading; this way the effect of Pt locality can be studied for two experimental carbon supports in isolation from all other parameters. For one carbon support, Pt active surface area and activity are significantly lower when nanoparticles are placed inside the pores. In contrast, for another, more graphitic carbon support, placing nanoparticles inside or outside of the carbon pores produces no appreciable difference in active surface area and performance rotating disk electrode measurements. Given their carefully tailored structure, these catalysts provide a framework for evaluating locality‐performance‐durability relationships. 

Pt nanoparticles supported on a library of 3d, 4d, 5d and f metal M–N–C catalysts for the ORR. 

Abstract The electrochemical reduction of nitrates (NO₃⁻) enables a pathway for the carbon neutral synthesis of ammonia (NH₃), via the nitrate reduction reaction (NO₃RR), which has been demonstrated at high selectivity. However, to make NH₃synthesis cost‐competitive with current technologies, high NH₃partial current densities (j_NH3) must be achieved to reduce the levelized cost of NH₃. Here, the high NO₃RR activity of Fe‐based materials is leveraged to synthesize a novel active particle‐active support system with Fe₂O₃nanoparticles supported on atomically dispersed Fe–N–C. The optimized 3×Fe₂O₃/Fe–N–C catalyst demonstrates an ultrahigh NO₃RR activity, reaching a maximum j_NH3of 1.95 A cm⁻²at a Faradaic efficiency (FE) for NH₃of 100% and an NH₃yield rate over 9 mmol hr⁻¹cm⁻². Operando XANES and post‐mortem XPS reveal the importance of a pre‐reduction activation step, reducing the surface Fe₂O₃(Fe³⁺) to highly active Fe⁰sites, which are maintained during electrolysis. Durability studies demonstrate the robustness of both the Fe₂O₃particles and Fe–N_xsites at highly cathodic potentials, maintaining a current of −1.3 A cm⁻²over 24 hours. This work exhibits an effective and durable active particle‐active support system enhancing the performance of the NO₃RR, enabling industrially relevant current densities and near 100% selectivity. 

Abstract Ionic liquids (ILs) have shown to be promising additives to the catalyst layer to enhance oxygen reduction reaction in polymer electrolyte fuel cells. However, fundamental understanding of their role in complex catalyst layers in practically relevant membrane electrode assembly environment is needed for rational design of highly durable and active platinum-based catalysts. Here we explore three imidazolium-derived ionic liquids, selected for their high proton conductivity and oxygen solubility, and incorporate them into high surface area carbon black support. Further, we establish a correlation between the physical properties and electrochemical performance of the ionic liquid-modified catalysts by providing direct evidence of ionic liquids role in altering hydrophilic/hydrophobic interactions within the catalyst layer interface. The resulting catalyst with optimized interface design achieved a high mass activity of 347 A g⁻¹_Ptat 0.9 V under H₂/O₂, power density of 0.909 W cm⁻²under H₂/air and 1.5 bar, and had only 0.11 V potential decrease at 0.8 A cm⁻²after 30 k accelerated stress test cycles. This performance stems from substantial enhancement in Pt utilization, which is buried inside the mesopores and is now accessible due to ILs addition. 

We developed a method, by combining electrochemical and electrokinetic streaming current techniques to study ion distribution and ionic conductivity in the diffuse part of electrochemical double layer (EDL) of a metal-electrolyte interface, when potential is applied on the metal by a potentiostat. We applied this method to an electrochemically clean polycrystalline gold (poly Au)-electrolyte interface and measured zeta potential for various applied potentials, pH, and concentration of the electrolyte. Specific adsorption of chloride ions on poly Au was studied by comparing measurements of zeta potential in KCl and KClO₄electrolytes. In absence of specific adsorption, zeta potential was found to increase linearly with applied potential, having slope of 0.04–0.06. When Cl⁻adsorption occurs, zeta potential changes the sign from positive to negative value at ∼750 mV vs Ag/AgCl applied potential. Complementary cyclic voltammetry and X-ray photoelectron spectroscopy studies were conducted to determine a degree of chloride ion adsorption on a poly Au. A correlation was observed between the applied potential at which zeta potential is zero and potential of zero charge for poly Au. Ion-distribution and ionic conductivity in the diffuse layer were calculated from the measured zeta potential data using nonlinear Poisson-Boltzmann distribution.