The cover art is attributed to an article entitled “Structural Control of PtNi Catalysts through Precise Synthesis Conditions and Elucidation of Property Determinants by operando XAS Analysis” by Weijie Cao et al. Editor’s Choice of this issue is a comprehensive investigation of the PtNi alloy nanowire as an efficient oxygen reduction reaction (ORR) catalyst.

Precise controlling in the shape of Pt-based alloy catalysts is an effective approach to enhance their catalytic ORR activity for proton exchange membrane fuel cell applications. In this study, the authors developed a standardized synthesis method for PtNi-alloy nanowire (NW) with outstanding ORR activity. Morphological observation combined with operando X-ray absorption spectroscopic analysis on the PtNi-alloy NWs revealed that surface roughness, high-index facet exposure, and electronic state of Pt under electrochemical conditions jointly contribute to the catalytic activity and durability.

PtNi alloy catalysts exhibit shape-dependent oxygen reduction reaction (ORR) activity and durability, influenced by synthesis conditions. In this study, a standardized synthesis method was developed by controlling the heating rate during nanowires (NWs) formation, yielding three distinct PtNi NW catalysts. Among these, PtNi-NW-3, featuring a rough surface with abundant high-index facets, demonstrated exceptional ORR activity and durability, achieving a mass activity of 1.06 A mg_Pt⁻¹ and a specific activity of 2.73 mA cm_Pt⁻², outperforming commercial Pt/C catalysts. The superior performance was attributed to reduced oxygen-binding energy and suppressed Pt oxidation, as revealed by operando high-energy-resolution fluorescence-detected X-ray absorption spectroscopy (HERFD-XAS). This work not only standardizes NW synthesis for improved reproducibility but also provides critical insights into the relationship between structural features and catalytic behaviours, paving the way for next-generation electrocatalysts.

Proton exchange membrane water electrolysis (PEMWE) has gathered significant interest as a method for hydrogen production. A crucial step in optimizing PEMWE performance is a pre-treatment process known as “conditioning” or “break-in”, during which a voltage or current is applied to the PEMWE prior to its actual operation. Despite its importance, the underlying mechanisms and improvements achieved through conditioning remain unclear. This study investigates the effects of conditioning on PEMWE, focusing on changes in the properties of the cation exchange polymer electrolyte membrane and the IrO₂ oxygen evolution catalyst. Results show that membrane conductivity increases and the valency of Ir changes from +3 to +5 by voltage application. The valency changes of Ir occur in two distinct voltage regions (0.8–1.0 and 1.3–1.5 V vs. cathode (CE)) when the applied voltage remains below the threshold for water electrolysis. Despite the intentional introduction of valence changes through applied voltage, no significant changes in the I-V characteristics within the water electrolysis region (from 1.5 to 2.0 V vs. CE) are observed. This is likely due to the fact that, at least as observed in linear sweep voltammetry, the activation time of Ir is sufficiently rapid that even the sweep rate of 10 mV/s is sufficient for activation.

The anion species dependence of the undetected solvent content in various aqueous lithium electrolyte solutions is discussed, and the quantitative behavior of near-infrared absorption due to intramolecular vibrations of dissolved species in the electrolyte is discussed in correlation with the Hofmeister series. It was observed that the number of water molecules measured by NIR spectroscopy was less than the theoretical value of the number of water molecules in solution, and the difference between the two increased with increasing concentration in the aqueous electrolyte solution. It is also observed that the undetected water amounts in ¹H qNMR and NIR spectra show clear anion dependences, specifically TFSA⁻ < ClO₄⁻ < Cl⁻ < NO₃⁻ < SO₄²⁻. The prominence of the undetected amount of water was found to be mainly due to the reduction of the peak at the low wavenumber region caused by water molecules with a well-developed hydrogen bonding network. It was observed that this feature almost follows the order of the Hofmeister series. Decrease in the absorbance of the water molecules in the NIR spectra are observed. The observed water molecules are predominantly those that have not interacted with the anions. It is suggested that the anion-water molecule interaction suppresses the generation of the combination band of OH symmetric stretching vibrations and OH asymmetric stretching vibrations of water molecules. The ¹H NMR quantitative analysis results are also consistent with the NIR results.

Various composite electrodes were prepared using Sn₄P₃ and other active materials (Sb, Bi, Ge, TiO₂, In, and Fe) with weight ratios of 70 and 30 wt% for Na-ion battery anode to improve capacity decay of Sn₄P₃ caused by Sn aggregation. No improvement was observed in the case of composite electrodes of Sn₄P₃/Ge and Sn₄P₃/TiO₂ due to poor electronic conductivities of Ge and TiO₂. Although In and Fe have good electronic conductivities, no improvement was achieved in Sn₄P₃/In and Sn₄P₃/Fe because of their low Na⁺ diffusion abilities. In contrast, the capacity decay was improved by the Sn₄P₃/Sb and Sn₄P₃/Bi electrodes. We consider that Sb and Bi have good electronic conductivity as well as Na⁺ diffusion ability, making it easier for electrons and Na⁺ to permeate the entire active material layer. In addition, the longest cycle life of 900 cycles was attained when the Sb addition amount was 15 wt%. This improvement was also achieved in Li-ion battery evaluation. Among the composite electrodes with various Sb amount, the longest cycle life was achieved by Sn₄P₃/Sb(85 : 15 wt%) electrode.

In this study, Al electroplating and anodization were performed to improve the wear resistance of the carbon fiber-reinforced plastic (CFRP) surface. The adhesion strength between the Al electroplating film and CFRP was improved by etching the resin part of the CFRP surface using a sulfuric acid treatment to increase the area occupied by the conductive carbon fibers. The surface roughness of CFRP increased with increasing etching time, resulting in CFRP surfaces with roughness of up to 8 µm. The adhesion strength between those etched surfaces and the Al-electroplated film increased with increasing etching time, and an anodized layer was formed on the CFRP substrate by anodizing the Al-electroplated film. The Vickers hardness of the anodizing layer was 318 Hv, which was approximately seven times higher than that of the CFRP substrate, i.e., 44 Hv.

The durability of protonic ceramic fuel cells (PCFCs) decreases owing to Co diffusion from the cathode into the electrolyte. To prevent Co diffusion during high-temperature cathode sintering and improve PCFC durability, this study proposes two methods: (1) low-temperature sintering of the Co-containing cathode and (2) the use of a Co-free cathode. Durability studies were conducted using anode-supported PCFCs with different cathodes: La_0.6Sr_0.4CoO_3−δ (LSCo)–BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3−δ (BCZYYb) sintered at 900 and 1100 °C, and La_0.65Ca_0.35FeO_3−δ (LCaF)–BCZYYb sintered at 1100 °C. Both cells with LSCo–BCZYYb cathodes exhibited low durability, regardless of sintering temperature. In contrast, cells with LCaF–BCZYYb cathodes demonstrated higher durability due to the absence of elemental diffusion and good adhesion at the cathode–electrolyte interface. The LCaF–BCZYYb cathode is a promising candidate for high-durability applications in PCFCs.

The paired electrolysis using the divided cell was successfully developed. The divided cell, equipped with a three-way cock in the center, was designed. It allowed the solution to be transferred from the cathode to the anode by using balloon pressure, after electrolysis. As the model reaction, the iminium ion by cation pool method and the in situ formation of allylsilanes were electrochemically prepared, and the solution was mixed in the same cell from the cathode to the anode to give the desired product involving C–C bond formation. The present method is an alternative to the electrochemical flow cell of paired electrolysis.

Surfactants possess unique properties in bulk solutions and at interfaces, naturally forming self-assembled structures. Herein, cetyltrimethylammonium trifluoroacetate (CTATFA) was incorporated into aqueous electrolytes as a cationic surfactant to enhance their ionic conductivity and electrochemical stability. The presence of CTATFA widened the electrochemical stability windows of both Li-based and Zn-based electrolytes. The Zn-based electrolyte exhibited high ionic conductivity and low viscosity in the bulk solution. In a Zn symmetric cell, the electrolyte containing 1 M Zn(TFA)₂-0.5 M CTATFA demonstrated excellent Zn plating/stripping reversibility for over 800 h at 1 mAh cm⁻² and 1 mA cm⁻². A Zn-Cu cell with 1 M Zn(TFA)₂-0.5 M CTATFA exhibited excellent reversibility, achieving over 300 plating/stripping cycles at 5 mA cm⁻² and 5 mAh cm⁻². The Zn/MnO₂ cell using the Zn-based electrolyte also demonstrated a specific capacity of 105 mAh g⁻¹ over 750 cycles at a current density of 0.5 A g⁻¹. This study provides insight into the design of high-performance aqueous electrolytes based on the self-assembly and surface adsorption of cationic surfactants.

Pure silicide electrodes have attracted attention as a promising anode material in lithium-ion batteries using certain ionic liquid electrolytes. However, the reaction mechanisms of silicide electrodes, particularly the lithiation sites in the crystal lattice and the reaction sites (bulk versus surface), remain unclear. Here, we investigated the electrochemical lithiation mechanism of a nickel silicide (NiSi₂) electrode. X-ray diffraction, transmission electron microscopy, and other techniques revealed that NiSi₂ phase did not separate and no lithiation of Si generated from NiSi₂ occurred. In contrast, ⁷Li magic angle spinning nuclear magnetic resonance demonstrated that stable deposition–dissolution of Li metal did not occur on the NiSi₂ electrode, and electrochemical lithiation of NiSi₂ proceeded. Additionally, we investigated the lithiation sites using computational chemistry. The peak positions in the nuclear magnetic resonance spectra differed from those predicted using the calculated valence electron numbers. This resulted from an increase in conduction electrons near the Fermi energy associated with the amount of Li stored in the NiSi₂ crystal lattice, followed by a Knight shift.

The influence of Zn²⁺ on the corrosion behavior of Ti in 1.68 mol L⁻¹ H₂SO₄ with 0.058 mol L⁻¹ F⁻ solutions was investigated by mass loss measurements, electrochemical tests, and surface observation and analysis. Different concentrations of Zn²⁺ (0.0002 mol L⁻¹, 0.002 mol L⁻¹, 0.02 mol L⁻¹, 0.2 mol L⁻¹) were added to the solutions to investigate the effect of Zn²⁺ concentration. The mass loss results showed that the presence of Zn²⁺ in the corrosive solution could accelerate the corrosion of Ti. From the electrochemical tests results, the corrosion resistance is decreased while increasing the Zn²⁺ concentration. An adsorption-desorption model of TiF_x^3−x on Ti was proposed: Zn²⁺ could inhibit the adsorption process of TiF_x^3−x and reduce the surface coverage of TiF_x^3−x, which could provide more active site for Ti to dissolve, resulted in the severe corrosion of Ti.