Human breath analysis of volatile organic compounds has gained significant attention recently because of its rapid and noninvasive potential to detect various metabolic diseases. The detection of ketones in the breath and blood is key to diagnosing and managing diabetic ketoacidosis (DKA) in patients with type 1 diabetes. It may also be of increasing importance to detect euglycemic ketoacidosis in patients with type 1 or type 2 diabetes or heart failure, treated with sodium-glucose transporter-2 inhibitors (SGLT2-i). The present research evaluates the efficiency of colorimetry for detecting acetone and ethanol in exhaled human breath with the response time, pH effect, temperature effect, concentration effect, and selectivity of dyes. Using the proposed multidye system, we obtained a detection limit of 0.0217 ppm for acetone and 0.029 ppm for ethanol in the detection range of 0.05−50 ppm. A smartphone-assisted unit consisting of a portable colorimetric device was used to detect relative red/green/blue values within 60 s of the interface for practical and real-time application. The developed method could be used for rapid, low-cost detection of ketones in patients with type 1 diabetes and DKA and patients with type 1 or type 2 diabetes or heart failure treated with SGLT2-I and euglycemic ketoacidosis.

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Lanthanum-based perovskites (LaMnxCo1-xO3 (0 ≤ x ≤ 1)) were synthesized using a solution combustion synthesis technique with variable ratios of Co and Mn to investigate the surface property and electrocatalytic characteristics (stability and activity of catalyst) for methanol oxidation reaction (MOR), oxygen reduction reaction (ORR), and oxygen evolution reaction (OER) under alkaline medium (KOH). The structural, chemical, and morphological characterizations of the synthesized catalyst were performed by XRD, FTIR, SEM, TEM, and XPS techniques as a function of the Mn:Co elemental ratio. The time–temperature profile during the combustion process was also monitored to study the completion of the combustion reaction and to understand its impact on the structure of the perovskites. SEM/EDX and XPS analysis confirmed the formation of the targeted ratio of Mn and Co on the catalyst. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) results revealed that all perovskite samples with different Co:Mn ratios were active for ORR, OER, and MOR. The LaMnxCo1-xO3 perovskite with x = 0.4 showed the highest current density compared to the other samples toward all the electrocatalytic reactions under alkaline reaction conditions. Graphical Abstract

We report the electrocatalytic properties of Ag-M/C (M=Cu, Zn, Fe, Cr, Mn) catalysts synthesized using the solution combustion synthesis (SCS) method for methanol oxidation reaction (MOR). The morphological properties of the synthesized catalysts were studied using scanning electron microscopy, energy-dispersive X-ray microscopy, tunneling electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS) techniques. The results indicated that AgCu/C is the most porous catalyst with small and well distributed nanoparticles making it a suitable choice for electrocatalytic applications. The XPS results showed a shift in peak in the AgCu/C sample due to the charge transfer between Ag and Cu indicating a strong interaction in the compound. The electrochemical measurements in 1 M methanol with 1 M KOH electrolyte by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) revealed that AgCu/C showed high electrocatalytic activity for MOR. Further studies on AgCu/C for methanol concentrations of 0.5 M, 1 M, 1.5 M, 2.5 M to evaluate the rate dependency of the catalyst indicated a power-law dependency with an order of 0.55 on methanol concentration. According to chronoamperometry analysis, the catalyst was stable for at least 20 hours.

Herein, we report the electrocatalytic properties of Ag-M/C (M=Cu, Zn, Fe, Cr, Mn) catalysts produced using solution combustion synthesis (SCS) method for methanol oxidation reaction (MOR). The morphological properties of the synthesized catalysts were studied using SEM, EDX, TEM, XRD and XPS techniques. The characterization results indicated that out of all catalysts, AgCu/C had the most porous surface, small and well distributed particles with high surface area making it a good choice for electrocatalytic experiments. The XPS results showed a shift in peak in the AgCu/C sample due to the charge transfer between Ag and Cu indicating a strong interaction between Ag and Cu. The electrochemical properties of the catalysts were studied at 1 M methanol concentration and 1 M KOH (electrolyte) concentration by performing Cyclic Voltammetry (CV) and Linear Sweep Voltammetry (LSV) experiments. It was observed that AgCu/C exhibited a greater electrocatalytic activity and was therefore, found to be a more viable catalyst for MOR. Following this, further concentration studies were conducted on AgCu/C for methanol concentrations of 0.5M, 1M, 1.5M, 2.5M to evaluate the rate dependency of the catalyst on MeOH concentration. The CV and LSV curves depicted a linear increase in current density proportional to the increase in methanol concentration, indicating power-law dependency. The catalyst also displayed long-term stability when chronoamperometry test was performed for 20 hours.

Corrigendum: Electrocatalytic Oxidation of Methanol Over Silver-based Ag-M/C (M=Cu, Zn, Fe, Cr, Mn) Electrocatalysts Synthesized by Solution Combustion Technique [J. Electrochem. Soc., 169, 054510 (2022)]

Lanthanum-based synthetic perovskites (LaMnxCo1-xO3 (0≤x≤1)) were synthesized using a solution combustion synthesis technique with variable ratios of Co and Mn to investigates the surface and electrocatalytic property (activity and stability of catalysts) for methanol oxidation reaction (MOR), oxygen reduction reaction (ORR), oxygen evolution reaction (OER) under alkaline medium (KOH). The structural and morphological characterizations of the synthesized catalyst were performed by XRD, FTIR, SEM, TEM and XPS techniques. The structural and chemical properties systematically changed by varying the Mn to Co ratio in the perovskite structure. To observe the completion of combustion and temperature characteristics during the synthesis process, which are known to impact structural qualities, the time temperature profile during the combustion process was monitored. SEM/EDX and XPS analysis confirmed the formation of targeted ratio of Mn and Co on the catalyst. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) results revealed that all perovskite samples with different Co:Mn ratios were active for ORR, OER and MOR. The LaMnxCo1-xO3 perovskite with x=0.4 showed the highest current density compared to other samples towards all the investigated electrocatalytic reactions (MOR, ORR and OER) under alkaline reaction conditions.