Exploring the Role of the Connection Length of Screen-Printed Electrodes towards the Hydrogen and Oxygen Evolution Reactions.

Zero-emission hydrogen and oxygen production are critical for the UK to reach net-zero greenhouse gasses by 2050. Electrochemical techniques such as water splitting (electrolysis) coupled with renewables energy can provide a unique approach to achieving zero emissions. Many studies exploring electrocatalysts need to "electrically wire" to their material to measure their performance, which usually involves immobilization upon a solid electrode. We demonstrate that significant differences in the calculated onset potential for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) can be observed when using screen-printed electrodes (SPEs) of differing connection lengths which are immobilized with a range of electrocatalysts. This can lead to false improvements in the reported performance of different electrocatalysts and poor comparisons between the literature. Through the use of electrochemical impedance spectroscopy, uncompensated ohmic resistance can be overcome providing more accurate Tafel analysis.

Effect of Intercalants inside Birnessite-Type Manganese Oxide Nanosheets for Sensor Applications.

Hydrazine is a common reducing agent widely used in many industrial and chemical applications; however, its high toxicity causes severe human diseases even at low concentrations. To detect traces of hydrazine released into the environment, a robust sensor with high sensitivity and accuracy is required. An electrochemical sensor is favored for hydrazine detection owing to its ability to detect a small amount of hydrazine without derivatization. Here, we have investigated the electrocatalytic activity of layered birnessite manganese oxides (MnO2) with different intercalants (Li+, Na+, and K+) as the sensor for hydrazine detection. The birnessite MnO2 with Li+ as an intercalant (Li-Bir) displays a lower oxidation peak potential, indicating a catalytic activity higher than the activities of others. The standard heterogeneous electron transfer rate constant of hydrazine oxidation at the Li-Bir electrode is 1.09- and 1.17-fold faster than those at the Na-Bir and K-Bir electrodes, respectively. In addition, the number of electron transfers increases in the following order: K-Bir (0.11 mol) < Na-Bir (0.17 mol) < Li-Bir (0.55 mol). On the basis of the density functional theory calculation, the Li-Bir sensor can strongly stabilize the hydrazine molecule with a large adsorption energy (-0.92 eV), leading to high electrocatalytic activity. Li-Bir also shows the best hydrazine detection performance with the lowest limit of detection of 129 nM at a signal-to-noise ratio of ∼3 and a linear range of 0.007-10 mM at a finely tuned rotation speed of 2000 rpm. Additionally, the Li-Bir sensor exhibits excellent sensitivity, which can be used to detect traces of hydrazine without any effect of interference at high concentrations and in real aqueous-based samples, demonstrating its practical sensing applications.

Unveiling a Novel Decomposition Pathway in Propylene Carbonate-Based Supercapacitors: Insights from a Jelly Roll Configuration Study.

This research elucidates novel insights into the electrochemical properties and degradation phenomena of propylene carbonate (PC)-based supercapacitors at a large-scale 18650 cylindrical jelly-roll cell level. Central to our findings is the identification of 2-ethyl-4-methyl-1,3-dioxolane (EMD) as a hitherto undocumented decomposition by-product, highlighting the nuanced complexity of PC electrolyte stability. We further demonstrate that elevated operational voltages precipitate accelerated electrolyte degradation, underscoring the criticality of defining the operational voltage window for maximizing device longevity. Employing advanced analytical techniques, including gas chromatography-mass spectrometry (GC-MS), this study meticulously analyzes electrolyte decomposition mechanisms. The outcomes offer pivotal insights into the operational constraints and chemical resilience of PC-based supercapacitors, contributing significantly to the optimization of supercapacitor design and application. By delineating a specific decomposition pathway, this investigation enriches the understanding of electrochemical dynamics in supercapacitor systems, providing a foundation for future research and technological advancement in energy storage devices.

Low-cost, facile droplet modification of screen-printed arrays for internally validated electrochemical detection of serum procalcitonin.

This manuscript presents the design and facile production of screen-printed arrays (SPAs) for the internally validated determination of raised levels of serum procalcitonin (PCT). The screen-printing methodology produced SPAs with six individual working electrodes that exhibit an inter-array reproducibility of 3.64% and 5.51% for the electrochemically active surface area and heterogenous electrochemical rate constant respectively. The SPAs were modified with antibodies specific for the detection of PCT through a facile methodology, where each stage simply uses droplets incubated on the surface, allowing for their mass-production. This platform was used for the detection of PCT, achieving a linear dynamic range between 1 and 10 ng mL-1 with a sensor sensitivity of 1.35 × 10-10 NIC%/ng mL-1. The SPA produced an intra- and inter-day %RSD of 4.00 and 5.05%, with a material cost of £1.14. Internally validated human serum results (3 sample measurements, 3 control) for raised levels of PCT (>2 ng mL-1) were obtained, with no interference effects seen from CRP and IL-6. This SPA platform has the potential to offer clinicians vital information to rapidly begin treatment for "query sepsis" patients while awaiting results from more lengthy remote laboratory testing methods. Analytical ranges tested make this an ideal approach for rapid testing in specific patient populations (such as neonates or critically ill patients) in which PCT ranges are inherently wider. Due to the facile modification methods, we predict this could be used for various analytes on a single array, or the array increased further to maintain the internal validation of the system.

Impact of cationic molecular length of ionic liquid electrolytes on cell performance of 18650 supercapacitors.

The specific cell capacitance, equivalent series resistance (ESR) and equivalent distributed resistance (EDR) of porous carbon-based supercapacitors linearly depend on the cationic molecular length of room-temperature ionic liquids.

Insight into the effect of intercalated alkaline cations of layered manganese oxides on the oxygen reduction reaction and oxygen evolution reaction.

The effect of the intercalated alkaline cations between the adjacent layers of multilayered manganese oxide (MnOx) towards the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) was investigated. Li-MnOx, Na-MnOx, K-MnOx, Rb-MnOx, and Cs-MnOx provide OER overpotentials of 1.64, 1.70, 1.79, 1.83, and 1.84 V vs. RHE, respectively as well as ORR overpotentials of 0.71, 1.06, 1.13, 1.15, and 1.14 V vs. RHE, respectively. Li-MnOx shows the highest bifunctional catalytic activity towards both the ORR and OER. In addition, the Gibbs free energy change of *OH adsorption is found to be the largest throughout the reaction pathways determining the rate of the whole ORR and OER.