The cover art is attributed to an article entitled “Effect of Coexisting TiO₂ Powder on Ionic Conduction of Highly Concentrated LiTFSA Aqueous Electrolyte (20.5 mol kg⁻¹)” by Jingchao Xu et al. This issue’s Editor’s Choice is an interesting study on the dependence of electrical conductivity on liquid-phase volume fraction in solid-liquid coexistence systems consisting of a highly concentrated LiTFSA electrolyte and TiO₂ powder.

The authors investigated solid-liquid coexistence systems comprising TiO₂ powder and highly concentrated LiTFSA aqueous electrolytes using electrical conductivity measurements and various spectroscopic methods. In this article, solid-phase and liquid-phase interactions were analyzed, and the influence of LiTFSA concentration on electrical conductivity changes with respect to the liquid-phase volume fraction was discussed.

The study investigates the optimization of auxiliary heating strategies during the cold start of fuel cells, analyzing the effects of factors such as bipolar plate materials, coolant types, positive temperature coefficient (PTC) heating power, initial current density, and coolant flow rate on cold start performance. The findings indicate that metal bipolar plates, due to their lower thermal mass, heat up faster than graphite bipolar plates, facilitating a quicker cold start. While coolant circulation enhances temperature distribution uniformity, it also increases the system’s thermal mass. Increasing PTC heating power can accelerate the heating process, but it offers limited improvements in cold start performance and increases energy consumption. Under conditions of −20 °C, by optimizing parameters such as current density and coolant flow rate, the fuel cell stack can achieve a cold start in approximately 55 s, significantly improving cold start performance and reducing energy consumption. This research provides optimized strategies for the application of fuel cells in cold environments.

Water electrolysis is a power-to-gas technology that can be used to decrease the effect of global warming. To reduce its overall cost, we have designed a water electrolysis system containing serially connected water electrolyzers that reduce the site area and increase energy efficiency. One of the issues remaining to be solved is to develop a method that can diagnose the degradation state of the water electrolyzer during operation without significantly changing the current supply. In this study, a diagnostic method, named the sweep method, was developed. A typical procedure of this method is described as follows. A linear sweeping current is applied to the multi-connected water electrolysis system. Then, swept current and response voltage measurements are collected and subjected to linear and nonlinear regression based on an equivalent circuit, -R₀-(R₁, C₁)-, to obtain its circuit parameters. The electrical resistance R₀ is elected as the evaluation criteria of the degradation, and the diagnostic results of sweep method are found to be close to those of an impedance analysis. As the method can be conducted without a significant current change, we believe that it can be applied to a large-scale water electrolysis system.

An electrical conductivity and its activation energy are measured for solid-liquid coexistence systems consisting of TiO₂ powder/highly concentrated LiTFSA aqueous electrolyte (20.5 mol kg⁻¹). The conductivity increases exponentially with an increase of the liquid content up to ca. 40 vol%, and the activation energy of the conductivity increases with a decrease of the liquid content below 35 vol%. Various spectroscopic measurement, such as Raman, near-infrared (NIR), and NMR spectra indicated that the presence of TiO₂ disrupts the nanoscale water channel structure in the water-enriched regions of the bulk solution in the TiO₂ powder/20.5 mol kg⁻¹ LiTFSA solid-liquid coexistence system with a liquid phase volume fraction below 40 vol%, resulting in an unusual decrease in the electrical conductivity. The strong influence of the solid phase on the electrical conduction of the highly concentrated LiTFSA electrolyte was found to be significant only in the region below 50 vol% in the liquid content, while in the region of the liquid content above 50 vol%, there were no differences due to electrolyte concentration and ion species, indicating the influence of the solid phase on electrical conduction.

Cleverly designing and synthesizing bifunctional electrocatalysts with high activity and exceptional stability for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) hold profound importance in the realm of renewable energy technologies. Here we demonstrated the fabrication of FeCoP hollow nanocubes by precisely controlling the oxidation-phosphorization processing on Prussian blue analogues. Owing to the robust electronic interaction and hollow structure, the obtained FeCoP material, when utilized for catalyzing HER and OER in a 1 M KOH solution, requires overpotentials of merely 74 mV and 219 mV to achieve 10 mA cm⁻², respectively. Importantly, when used as a bifunctional catalyst for overall water splitting, FeCoP can achieve a current density of 10 mA cm⁻² at a low cell voltage of only 1.58 V and exhibits impressive durability. After a prolonged test of 52 hours under a constant current density, there is no significant degradation performance decay. The current method offers a broader avenue for the controllable synthesis of phosphide electrocatalysts in practical applications.

This study introduces a novel low-temperature electrochemical flow reactor for the efficient trichloromethylation of benzaldehyde using electrogenerated bases (EGBs). The setup achieved precise temperature control by leveraging a Peltier-cooled system and a divided flow reactor with carbon-felt electrodes without requiring external cooling baths. Optimization of reaction parameters, including flow rate, temperature, and charge passed, resulted in a maximum yield of 67 % for 2,2,2-trichloro-1-phenylethanol, demonstrating significantly enhanced stability and reactivity of EGBs. This system exhibits a productivity of 1.01 mmol h⁻¹, which is 6.7 times higher than that of a prior microflow reactor approach, and successfully scales up to reactions involving 5 mmol of substrate. Cooling was identified as a critical factor in stabilizing the reactive intermediates, while further experiments confirmed the inefficacy of external cooling components alone. This robust and scalable reactor design highlights the potential for advancing low-temperature electrochemical synthesis and unlocking new reaction pathways.

The electrochemical deposition and dissolution of Al with an electrolyte solution containing dimethyl sulfone and aluminum chloride was investigated at 30 °C to determine the reversibility of the process. Although aluminum deposition was observed in the electrolyte solution containing dimethyl sulfone and aluminum chloride, multiple oxidation peaks were observed in the dissolution reaction. The morphology of the deposited aluminum was observed using a scanning electron microscope, and it was found that the shape of the aluminum deposits varied greatly depending on the deposition potential. Electrochemical measurements under various conditions revealed that the oxidative decomposition of the electrolyte at the Al counter electrode during the aluminum deposition on the working electrode resulted in a large amount of aluminum oxide contamination in the deposited aluminum. To prevent such a reaction, we designed a cell in which the potential of the counter electrode did not exceed the electrochemical potential window and observed a very reversible aluminum deposition dissolution reaction. Finally, we successfully charged/discharged the Al negative electrode using a dimethyl sulfone-based electrolyte. These findings are important because the electrolytes with dimethyl sulfone and aluminum chloride are compatible as electrolytes for rechargeable aluminum batteries and because they highlight the precautions that need to be taken in their application.