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Nitrate is a water-soluble toxic pollutant that needs to be excluded from the environment. For this purpose, several electrochemical studies have been conducted but most of them focused on the nitrate reduction reaction (NRR) in alkaline and acidic media while insignificant research is available in neutral media with Pt electrode. In this work, we explored the effect of three coinage metals (Cu, Ag, and Au) on Pt electrode for the electrochemical reduction of nitrate in neutral solution. Among the three electrodes, Pt-Cu exhibited the best catalytic activity toward NRR, whereas Pt-Au electrode did not show any reactivity. An activity order of Pt-Cu > Pt–Ag > Pt-Au was observed pertaining to NRR. The Pt–Ag electrode produces nitrite ions by reducing nitrate ions ( NO 3 - → NO 2 - ) . Meanwhile, at Pt-Cu electrode, nitrate reduction yields ammonia via both direct ( NO 3 - → NH 3 ) and indirect ( NO 3 - → NO 2 - → NH 3 ) reaction pathways depending on the potential. The cathodic transfer coefficients were estimated to be ca. 0.40 and ca. 0.52, while the standard rate constants for nitrate reduction were calculated as ca. 2.544 × 10 –2  cm.s −1 and ca. 1.453 × 10 –2  cm.s −1 for Pt-Cu and Pt–Ag electrodes, respectively. Importantly, Pt-Cu and Pt–Ag electrodes execute NRR in the neutral medium between their respective Hydrogen-Evolution Reaction (HER) and Open-Circuit Potential (OCP), implying that on these electrodes, HER and NRR do not compete and the latter is a corrosion-free process.

The pursuit of electrochemical carbon dioxide reduction reaction (CO2RR) as a means of energy generation and mitigation of global warming is of considerable interest. In this study, a novel RuO2-incorporated SnO2-fabricated glassy carbon electrode (GCE) with a Nafion binder was used for the electrochemical reduction of CO2 in an aqueous alkaline imidazole medium. The electrode fabrication process involved the drop-casting method, where RuO2.SnO2 was incorporated onto the surface of the GCE. Electrochemical studies demonstrated that the GCE-RuO2.SnO2 electrode facilitated CO2 reduction at −0.58 V vs. the reversible hydrogen electrode (RHE) via a diffusion-controlled pathway with the transfer of two electrons. Importantly, the first electron transfer step was identified as the rate-determining step (RDS). A Tafel slope of 144 mV dec−1 confirmed the association of two-electron transfer kinetics with CO2RR. Moreover, the standard rate constant (ko) and formal potential (E°′) were evaluated as 2.89 × 10−5 cm s−1 and 0.0998 V vs. RHE, respectively. Kinetic investigations also reveal that the deprotonation and electron release steps took place simultaneously in the CO2RR. Based on the reported results, the GCE-RuO2.SnO2 electrode could be a promising candidate for CO2 reduction, applicable in renewable energy generation.

Here, a sensitive voltametric electrochemical sensor probe was fabricated to reliably trace the detection of L-aspartic acid in phosphate-buffered medium using a glassy carbon electrode (GCE) layered with a film of wet-chemically prepared Ag2O-doped ZnO nanosheets (NSs). EDS, FESEM, XPS, and X-ray diffraction analyses were implemented as characterizing tools of prepared NSs to confirm the structural and compositional morphology, binding energies of existing atoms, and the crystallinity of synthesized NSs. The differential pulse voltammetry (DPV) was applied to the trace detection of L-aspartic acid, and exhibited a wide detection range of 15.0~105.0 µM, a limit of detection (3.5 ± 0.15 µM), and good sensitivity (0.2689 µA µM−1 cm−2). Besides these the precious reproducibility, stability, and efficient responses were perceived from the voltametric analysis of aspartic acid. Moreover, the proposed aspartic acid was subjected to experiments to potentially detect aspartic acid in real biological samples. Therefore, the development of an enzyme-free sensor by applying this method will be a smart technical approach in the near future.

Chlorazol yellow (CY) is a commonly used anionic, toxic, mutagenic, and potentially carcinogenic azo dye, which is menacing to the environment, aquatic system, food chain, and human health as well. To remove CY dye molecules from an aqueous medium, a series of Ce, Bi, and N co-doped TiO 2 photocatalysts were prepared by varying the composition of the dopants. Under sunlight irradiation, the resultant 5 wt% (Ce-Bi-N) co-doped TiO 2 composite catalyst was found to show the best catalytic activity. Hence, the required characterization of this catalyst was performed systematically using energy-dispersive X-ray spectroscopy (EDX), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) techniques. From the thorough investigation, it is revealed that the CY molecules reached adsorption–desorption equilibrium onto the surface of the catalyst within 30 min following second-order kinetics. Herein, the catalyst attained 97% degradation when exposed to sunlight at neutral (pH ~ 7, [CY] = 5 mg L −1 ) medium. The developed catalyst can destruct CY molecules with a maximum rate of 23.1 µg CY g −1  min −1 and the photodegradation kinetics follows first-order kinetics below 23.5 mg L −1 , a fractional order between 23.5 and 35.0 mg L −1 , and a zeroth order above 35.0 mg L −1 of CY concentration. Finding from scavenging effect implies that O 2 - and OH ∙ radicals have significant influence on the degradation. A suitable mechanism has been proposed with excellent stability and verified reusability of the proposed photocatalyst.

The development of efficient and non-toxic fuels for direct liquid fuel cells has highlighted ascorbic acid (AA) as a sustainable energy source. This study presents a combined theoretical and experimental investigation of ascorbate oxidation on an Au-Pt electrode in alkaline medium. Density functional theory (DFT) calculations reveal that Au deposition on Pt creates a more homogeneous and active surface, significantly enhancing the adsorption energy of ascorbate (−7.54 eV vs. −5.80 eV on bare Pt). Electrochemically, this translates to a superior performance, where the Au-Pt electrode achieves a 38% reduction in charge-transfer resistance, a higher current density, and a lower Tafel slope of 77 mV dec−1, indicating accelerated kinetics. The electrode also retains its activity over 1000 cycles, confirming exceptional durability. This synergistic combination of theoretical and experimental results establishes Au-Pt as a premier catalyst for sustainable ascorbate-based energy conversion.

A hydrogen fuel cell is a highly promising alternative to fossil fuel sources owing to the emission of harmless byproducts. However, the operation of hydrogen fuel cells requires a constant supply of highly pure hydrogen gas. The scarcity of sustainable methods of producing such clean hydrogen hinders its global availability. In this work, a noble Au-atom-decorated glassy carbon electrode (Au/GCE) was prepared via a conventional electrodeposition technique and used to investigate the generation of hydrogen from acetic acid (AA) in a neutral electrolyte using 0.1 M KCl as the supporting electrolyte. Electrochemical impedance spectroscopy (EIS), open circuit potential measurement, cyclic voltammetry (CV), and rotating disk electrode voltammetry (RDE) were performed for the characterization and investigation of the catalytic properties. The constructed catalyst was able to produce hydrogen from acetic acid at a potential of approximately −0.2 V vs. RHE, which is much lower than a bare GCE surface. According to estimates, the Tafel slope and exchange current density are 178 mV dec−1 and 7.90×10−6 A cm−2, respectively. Furthermore, it was revealed that the hydrogen evolution reaction from acetic acid has a turnover frequency (TOF) of approximately 0.11 s−1.

Groundwater is the principal source of drinking water for the residents of the Bengal Delta Plain. However, its quality has reportedly been declining due to various anthropogenic and geogenic activities. Therefore, it is crucial to investigate the current status of groundwater quality for sustainable resource management. This study aims to assess the current groundwater chemistry and evaluate the drinking water quality in the northwestern region of Bangladesh within the Bengal Delta, using multivariate statistical methods and water quality index (WQI) calculation. Data on various water quality parameters—fluoride, calcium, chloride, potassium, sodium, ammonium, nitrate, magnesium, pH, electrical conductivity (EC), water hardness, TOC, sulfate, carbonate, bicarbonate, trace and heavy metal profiles—were obtained from 128 sites across five sub-districts (also known as Upazila) in north-western Bangladesh. The results indicate that majority of the parameters met the standards defined by the WHO, except for NO 3 − in Baliadangi Upazila, where the study identified the underlying cause of this NO 3 − contamination. The WQI classified the 120 samples as follows: 55.00% were excellent, 34.17% were good, 10.00% were poor, and 0.83% were unfit for consumption. The groundwater samples in the region were free from heavy metals and contained permissible amounts of trace metals. The cluster analysis (CA) and principal component analysis (PCA) identified diverse ions in various Upazilas as the influencing factors in water chemistry, primarily originating from either carbonate or silicate weathering processes. Overall, this study provides valuable insights into groundwater chemistry and quality, serving as a resource for those concerned with sustainable groundwater management.

Water pollution has badly affected human health, aquatic life, and the ecosystem. The purity of surface water can be measured in terms of dissolved oxygen (DO) measurements. Hence, it is desirable to have a portable and simple-to-use dissolved oxygen sensor. One possible remedy is an electrochemical sensor. Thus, we proposed an ITO-IrOx electrocatalyst for an effective and interference-free DO sensor utilizing the principle of oxygen reduction reaction (ORR). The ITO-IrOx was characterized using cyclic voltammetry (CV), scanning electron microscopy (SEM), electrochemical impedance spectrometry (EIS), X-ray photoelectron spectroscopy (XPS), and reflectance spectroscopy-based techniques. Reflectance spectra of the ITO-IrOx electrode showed the photoresist capability. The EIS spectra revealed lower charge transfer resistance for the ITO-IrOx electrode in ORR. The IrOx film on ITO exhibited a quick (one electron, α = 1.00), and reversible electron transfer mechanism. The electrode demonstrated high stability for oxygen sensing, having a limit of detection (LOD) of 0.49 ppm and interference-free from some common ions (nitrate, sulphate, chloride etc.) found in water.

This article describes how selectively anionic organic molecules could be removed from aqueous medium using naturally available gypsum (GS) adsorbent. Gypsum (CaSO4.2H2O) shows strong interactions with anionic dye molecules while it dos not show any affinity towards cationic dye molecules. We have shown the removal efficiency of gypsum taking chlorazole yellow (anionic dye) and methylene blue (cationic dye) as examples of adsorbates. The GS has been to be even more effective than activated carbon in attaining chlorazole yellow (CY) removal. Three well-known kinetic equations e.g. pseudo-first-order, pseudo-second order and intraparticle diffusion were exploited to interpret the experimental data. Results show best fitting with second order kinetic process with excellent regression coefficient (r2 = 0.99) for the adsorption process. The equilibrium data were analyzed exploiting some adsorption isotherm models. It was apparent that the Freundlich isotherm model superbly fitted for CY dye adsorption process. And the maximum adsorption capacity, Qm, was obtained as 12.85 mg g−1 at room temperature. The negative values of Gibb’s free energy change (ΔGo) suggests that the CY dye molecule adsorption process is spontaneous in nature. Moreover, negative enthalpy change (ΔHo) indicates the exothermic nature of the adsorption process. The outcome could be exploited where anionic organic molecules are required to be separated, selectively.

Electrochemical techniques were successfully employed to estimate contamination of water of river Buriganga, Bangladesh. A Pt–Cu electrode has been exploited to measure selective nitrate concentration, and corrosion rate of iron has been proposed to indicate relative abundance of dissolved contaminants. In order to evaluate the pollution level, water parameters of river Buriganga have been compared with those obtained from two freshwater streams named Surma and Dawki of the country. An iron strip in contact with Buriganga river water is corroded three times rapidly compared to its contact with Dawki or Surma river water indicates acute contamination of Buriganga river water. The River Buriganga is facing acute pollution from the point of high TDS (0.664–0.694 g/L), low DO (1.47–4.4 mg/L), high COD (197–218 mg/L), high ammonia (270–420 mg/L) and high nitrate concentration (107–157 mg/L). Negative ORP value (− 292 to − 310 mV) of Buriganga river water indicates that the stream contains high level reducing species. Meanwhile, positive ORP value indicates that Dawki (+ 203 to + 209 mV) and Surma (+ 184 to + 205 mV) river water contain oxidizing species. Sediment analysis shows the deposition of disintegrated organic pollutants on the bottom of the River Buriganga. Cost-effective carbon material synthesized from taro stems has been proposed to restore water parameters of filthy water system like Buriganga river.