Electrocatalytic Activity For Reduction Research Articles

Highly improved ionic conduction in reverse spinel structured CoAl2O4 and ZnO heterostructure through interfacial disordering

For ceramic fuel cells with low temperatures operation (LT-CFCs; 350°-550 °C), increasing the ionic conductivity and improving the oxygen reduction electrocatalytic activity response at low operating temperatures would be highly desired. This Study presents a novel semiconductor heterostructure composite with a competent electrolyte membrane for LT-CFCs. The composite comprises CoAl2O4 (CA) in a spine-like structure and wurtzite-structured ZnO. We have demonstrated a button-sized CFC under H2 and ambient air environment delivering a high power density of 835 mW-cm−2 at 550 °C, with potential operating up-to 400 °C. Compared to ZnO and CA alone, the CA-ZnO heterostructure composite has reduced oxygen vacancy production and activation energy, facilitating ion transport more quickly through the CA-Zn interface. Density functional theory (DFT) computations, photoelectron spectroscopy, U-visible, X-ray diffraction, and HR-TEM are the characterization techniques used to study the enhanced ionic conduction of the CA-ZnO heterostructure composite. These results imply that the heterostructure approach works better than the simple bulk structure for the electrolyte application of LT-SOFCs.

Thermal-driven Dispersion of Bismuth Nanoparticles among Carbon Matrix for Efficient Carbon Dioxide Reduction.

The poor electrocatalytic stability and rapid deactivation of metal electrocatalysts are always present in the electrocatalytic conversion of carbon dioxide (CO2) due to the harsh reduction condition. Herein, we demonstrate the controllable dispersion of ultrafine bismuth nanoparticles among the hollow carbon shell (Bi@C-700-4) simply by a thermal-driven diffusion process. The confinement effect of nitrogen-doped carbon matrix is able to low the surface energy of bismuth nanoparticles against the easy aggregation commonly observed for the thermal treatment. On the basis of the synergistic effect and confinement effect between bismuth nanoparticles and carbon matrix, the highly dispersed active sites render the obviously improved electrocatalytic activity and stability for carbon dioxide reduction into formate. The in-situ experimental observation on the reduction process and theoretical calculations reveal that the incorporation of bismuth nanoparticles with nitrogen-doped carbon matrix would promote the activation of CO2 and the easy formation of key intermediate (*OCHO), thus leading the enhanced electrocatalytic activity, with a Faradaic Efficiency (FE) of formate about 94.8% and the long-time stability. Furthermore, the coupling of an anode for 5-hydroxymethylfurfural oxidation reaction (HMFOR) in solar-driven system renders the high 2,5-furandicarboxylic acid (FDCA) yield of 81.2%, presenting the impressive solar-to-fuel conversion.

Thermal‐driven Dispersion of Bismuth Nanoparticles among Carbon Matrix for Efficient Carbon Dioxide Reduction

The poor electrocatalytic stability and rapid deactivation of metal electrocatalysts are always present in the electrocatalytic conversion of carbon dioxide (CO2) due to the harsh reduction condition. Herein, we demonstrate the controllable dispersion of ultrafine bismuth nanoparticles among the hollow carbon shell (Bi@C‐700‐4) simply by a thermal‐driven diffusion process. The confinement effect of nitrogen‐doped carbon matrix is able to low the surface energy of bismuth nanoparticles against the easy aggregation commonly observed for the thermal treatment. On the basis of the synergistic effect and confinement effect between bismuth nanoparticles and carbon matrix, the highly dispersed active sites render the obviously improved electrocatalytic activity and stability for carbon dioxide reduction into formate. The in‐situ experimental observation on the reduction process and theoretical calculations reveal that the incorporation of bismuth nanoparticles with nitrogen‐doped carbon matrix would promote the activation of CO2 and the easy formation of key intermediate (*OCHO), thus leading the enhanced electrocatalytic activity, with a Faradaic Efficiency (FE) of formate about 94.8% and the long‐time stability. Furthermore, the coupling of an anode for 5‐hydroxymethylfurfural oxidation reaction (HMFOR) in solar‐driven system renders the high 2,5‐furandicarboxylic acid (FDCA) yield of 81.2%, presenting the impressive solar‐to‐fuel conversion.

Theoretical calculations and experimental verification of carbon dioxide reduction electrocatalyzed by metalloporphyrin

Metal-functionalized porphyrin-like graphene structures are promising electrocatalysts for carbon dioxide reduction reaction (CO2RR) as their metal centers can modulate activity. Yet, the role of metal center of metalloporphyrins (MTPPs) in CO2 reaction activity is still lacking deep understanding. Here, CO2RR mechanism on MTPPs with five different metal centers (M = Fe, Co, Cu, Zn and Ni) are examined by first-principles calculations. The *COOH formation is the rate determined step on the five MTPP structures, and the CoTPP exhibits the best CO2RR activity while ZnTPP and NiTPP are the worst, which is also verified by our experiment. The CO2RR activity is controlled by adsorption states of intermediates (*CO, *COOH), i.e., chemisorption (e.g., on CoTPP) and physisorption (on ZnTPP and NiTPP) of intermediates will lead to good and poor activity, respectively. The deeper the d-band center of the porphyrin ring complexed metal atom, the weaker bonding of MTPP with CO and COOH. Theoretical calculations and experimental results indicate that MTPPs with Co and Fe centers lead to a reduction in the energy barriers for the two uphill reaction steps in the electrocatalytic CO2 reduction process, thereby enhancing CO2 reduction electrocatalytic activity. Faradaic efficiency of CO is correlated with the reaction energy barrier of the first proton-coupled electron reduction process, displaying a strong linear correlation. This work provides a fundamental understanding of MTPPs used as electrocatalysts for CO2RR.

Advancing electrochemical nitrogen reduction: Efficacy of two-dimensional SiP layered structures with single-atom transition metal catalysts

Researchers are interested in single-atom catalysts with atomically scattered metals relishing the enhanced electrocatalytic activity for nitrogen reduction and 100 % metal atom utilization. In this paper, we investigated 18 transition metals (TM) spanning 3d to 5d series as efficient nitrogen reduction reaction (NRR) catalysts on defective 2D SiPV layered structures through first-principles calculation. A systematic screening identified Mo@SiPV, Nb@SiPV, Ta@SiPV and W@SiPV as superior, demonstrating enhanced ammonia synthesis with significantly lower limiting potentials (−0.25, −0.45, −0.49 and −0.15 V, respectively), compared to the benchmark −0.87 eV for the defective SiP. In addition, the descriptor ΔG*N was introduced to establish the relationship between the different NRR intermediates, and the volcano plot of the limiting potentials were determined for their potential-determining steps (PDS). Remarkably, the limiting voltage of the NRR possesses a good linear relationship with the active center TM atom Ɛd, which is a reliable descriptor for predicting the limiting voltage. Furthermore, we verified the stability (using Ab Initio Molecular Dynamics − AIMD) and high selectivity (UL(NRR)-UL(HER) > -0.5 V) of these four catalysts in vacuum and solvent environments. This study systematically demonstrates the strong catalytic potential of 2D TM@SiPV(TM = Mo, Nb, Ta, W) single-atom catalysts for nitrogen reduction electrocatalysis.

Red Carbon Mediated Formation of Cu2O Clusters Dispersed on the Oxocarbon Framework by Fehling's Route and their Use for the Nitrate Electroreduction in Acidic Conditions.

The oligomers of carbon suboxide, known as red carbon, exhibit a highly conjugated structure and semiconducting properties. Upon mild heat treatment, it transforms into a carbonaceous framework rich in oxygen surface terminations, called oxocarbon. In this study, the abundant oxygen functionalities are harnessed as anchors to create oxocarbon-supported nanohybrid electrocatalysts. Starting with single atomic Cu (II) strongly coordinated to oxygen atoms on red carbon, the Fehling reaction leads to the formation of Cu2O clusters. Simultaneously, a covalent oxocarbon framework emerges via cross-linking, providing robust support for Cu2O clusters. Notably, the oxocarbon support effectively stabilizes Cu2O clusters of very small size, ensuring their high durability in acidic conditions and the presence of ammonia. The synthesized material exhibits a superior electrocatalytic activity for nitrate reduction under acidic electrolyte conditions, with a high yield rate of ammonium (NH4 +) at 3.31mmolh-1mgcat -1 and a Faradaic efficiency of 92.5% at a potential of -0.4V (vs RHE).

Facile Fabrication of an SnSx‐SnO2‐Decorated Cobalt Sulfide Film as an Effective Counter Electrode for Dye‐Sensitized Solar Cells

AbstractMetal sulfide stands out as one of the novel and promising platinum‐free counter electrode (CE) materials for dye‐sensitized solar cells (DSSCs). In this work, SnSx‐SnO2‐decorated CoSx films were designed and synthesized by a low‐temperature fabrication process. The small clusters of nanoparticles create a large amount of catalytic active sites, resulting in superior electrocatalytic activity for triiodide reduction. The DSSC with SnSx‐SnO2‐decorated CoSx film has achieved an impressive power conversion efficiency of 4.57 %, which is close to the efficiency of the DSSC with platinum CE (4.82 %). Furthermore, regarding the attenuation of the photovoltaic performance for the DSSC with SnSx‐SnO2‐decorated CoSx film, negligible change was observed after a prolonged storage under ambient condition for five days. Therefore, it is worthwhile to expect the explorations of novel fabricate technique for synthesizing cost‐effective metal sulfide films with long‐term stability in DSSCs.

Nanobioelectrocatalysis Using Human Liver Microsomes and Cytochrome P450 Bactosomes: Pyrenyl-Nanocarbon Electrodes.

Human liver microsomes containing various drug-metabolizing cytochrome P450 (P450) enzymes, along with their NADPH-reductase bound to phospholipid membranes, were absorbed onto 1-pyrene butylamine pi-pi stacked with amine-functionalized multiwalled carbon nanotube-modified graphite electrodes. The interfaced microsomal biofilm demonstrated direct electrochemical communication with the underlying electrode surface and enhanced oxygen reduction electrocatalytic activity typical of heme enzymes such as P450s over the unmodified electrodes and nonenzymatic currents. Similar enhancements in currents were observed when the bioelectrodes were constructed with recombinant P450 2C9 (single isoform) expressed bactosomes. The designed liver microsomal and 2C9 bactosomal bioelectrodes successfully facilitated the electrocatalytic conversion of diclofenac, a drug candidate, into 4'-hydroxydiclofenac. The enzymatic electrocatalytic metabolite yield was several-fold greater on the modified electrodes than on the unmodified bulk graphite electrodes adsorbed with a microsomal or bactosomal film. The nonenzymatic metabolite production was less than the enzymatically catalyzed metabolite yield in the designed microsomal and bactosomal biofilm electrodes. To test the throughput potential of the designed biofilms, eight-electrode array configurations were tested with the microsomal and bactosomal biofilms toward electrochemical 4'-hydroxydiclofenac metabolite production from diclofenac. The stability of the designed microsomal bioelectrode was assessed using nonfaradaic impedance spectroscopy over 40 h, which indicated good stability.

Atomic Force Microscopy (AFM) Tip based Nanoelectrode with Hydrogel Electrolyte and Application to Single-Nanoparticle Electrochemistry

<p>An unconventional fabrication technique of nanoelectrode was developed using atomic force microscopy (AFM) and hydrogel. Until now, the precise control of electroactive area down to a few nm<sup>2</sup> has always been an obstacle, which limits the wide application of nanoelectrodes. Here, the nanometer-sized contact between the boron-doped diamond (BDD) as conductive AFM tip and the agarose hydrogel as solid electrolyte was well governed by the feedback amplitude of oscillation in the non-contact mode of AFM. Consequently, this low-cost and feasible approach gives rise to new possibilities for the fabrication of nanoelectrodes. The electroactive area controlled by the set point of AFM was investigated by cyclic voltammetry (CV) of the ferrocenmethanol (FcMeOH) combined with quasi-solid agarose hydrogel as an electrolyte. Single copper (Cu) nanoparticle was deposited at the apex of the AFM tip using this platform whose electrocatalytic activity for nitrate reduction was then investigated by CV and Field Emission-Scanning Electron Microscopy (FE-SEM), respectively.</p>

N-doped lotus seedpods biocarbon hybridized with NiCo2S4 as counter electrodes for dye sensitized solar cells

A facile and green approach to composites containing nitrogen doped lotus seedpods biocarbon (NALC) and NiCo2S4 (NCS) is reported. The composites present excellent electrocatalytic activity for reduction from I3− to I− due to the synergistic effect between the nanocrystalline NCS and the NALC. Dye-sensitized solar cells (DSSCs) assembled with the as-prepared NALC@NCS counter electrodes (CEs) achieve impressive photovoltaic conversion efficiency (PCE) of 8.58%, which is higher than that by the same structured cell with Pt (7.85%) and NCS (7.53%) CEs. Compared with other NCS based CEs, the NALC@NCS CEs show good durability and stability, suggesting that combining nanocrystalline catalyst with biocarbon is beneficial to stimulate the synergistic effect, and is a feasible strategy to optimal CEs for high performance DSSCs. Low cost NALC@NCS composites developed in this work are environmentally friendly, stable and efficient, which are believed to be good candidates for Pt-free CE materials in DSSCs and electrocatalysis applications.

Improved capacitive performances and electrocatalytic reduction activity by regulating the bonding interaction between Zn-bistriazole-pyrazine/pyridine units and diverse Anderson-type polyoxometalates.

Electrochemical performances can be effectively improved by introducing metal-organic units (MOUs) into polyoxometalates (POMs). However, regulating the bonding strength between POMs and MOUs at the molecular level to improve the electrochemical performance is a challenging task. Three new POM-based metal-organic complexes (MOCs), namely H{Zn2(Hpytty)2(H2O)8[CrMo6(OH)6O18]}·2H2O (1), H{Zn2(Hpyttz)2(H2O)6[CrMo6(OH)6O18]}·8H2O (2), and {(μ2-OH)2Zn6(pyttz)2(H2O)10[TeMo6O24]}·2H2O (3) (H2pytty = 3-(pyrazin-2-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl, H2pyttz = 3-(pyrid-2-yl)-5-(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl), were obtained. Single-crystal X-ray diffraction shows that the bonding strength (from the hydrogen bond to the coordination bond) between Zn-bistriazole-pyrazine/pyridine units and diverse Anderson-type POMs gradually increases from complexes 1 to 3. Glassy carbon electrodes modified with complex 3 (3-GCE) has the highest specific capacitance, which is 930 F g-1 at 1 A g-1. Moreover, carbon paste electrodes (1-3-CPEs) modified with complexes 1-3 are used as electrochemical sensors for detecting Cr(VI) ions, with limits of detection well below the World Health Organization (WHO) maximum level in drinking water.

Electrochemical reconstruction of a 1D Cu(PyDC)(H2O) MOF into in situ formed Cu-Cu2O heterostructures on carbon cloth as an efficient electrocatalyst for CO2 conversion.

Electrochemical carbon dioxide (CO2) conversion has enormous potential for reducing high atmospheric CO2 levels and producing valuable products simultaneously; however the development of inexpensive catalysts remains a great challenge. In this work, we successfully synthesised a 1D Cu-based metal-organic framework [Cu(PyDC)(H2O)], which crystallizes in an orthorhombic system with the Pccn space group, by the hydrothermal method. Among the different catalysts utilized, the heterostructures of cathodized Cu-Cu2O@CC demonstrate increased efficiency in producing CH3OH and C2H4, achieving maximum FE values of 37.4% and 40.53%, respectively. Also, the product formation rates of CH3OH and C2H4 reach up to 667 and 1921 μmol h-1 cm-2. On the other side, Cu-Cu2O/NC-700 carbon composites simultaneously produced C1-C3 products with a total FE of 23.27%. Furthermore, a comprehensive study involving detailed DFT simulations is used to calculate the energetic stability and catalytic activity towards the CO2 reduction of Cu(111), Cu2O(111), and Cu@Cu2O(111) surfaces. During the early phase of electrochemical treatment, Cu(II) carboxylate nodes (Cu-O) in the Cu(PyDC)(H2O) MOF were reduced to Cu and Cu2O, with a possible synergistic enhancement from the PyDC ligands. Thus, the improved activity and product enhancement are closely associated with the cathodized reconstruction of Cu-Cu2O@CC heterostructures on carbon cloth. Hence, this study provides efficient derivatives of Cu-based MOFs for notable electrocatalytic activity in CO2 reduction and gives valuable insights towards the advancement of practical CO2 conversion technology.

The rigidity and chelation effect of ligands on the hydrogen evolution reaction catalyzed by Ni(II) complexes.

With increasing interest in nickel-based electrocatalysts, three heteroleptic Ni(II) dithiolate complexes with the general formula [Ni(II)L(L')2] (1-3), L = 2-(methylene-1,1'-dithiolato)-5,5'-dimethylcyclohexane-1,3-dione and L' = triphenylphosphine (1), 1,1'-bis(diphenylphosphino)ferrocene (DPPF) (2), and 1,2-bis(diphenylphosphino)ethane (DPPE) (3), have been synthesized and characterized by various spectroscopic techniques (UV-vis, IR, 1H, and 31P{1H} NMR) as well as the electrochemical method. The molecular structure of complex 2 has also been determined by single-crystal X-ray crystallography. The crystal structure of complex 2 reveals a distorted square planar geometry around the nickel metal ion with a NiP2S2 core. The cyclic voltammograms reveal a small difference in the redox properties of complexes (ΔE° = 130 mV) while the difference in the catalytic half-wave potential becomes substantial (ΔEcat/2 = 670 mV) in the presence of 15 mM CF3COOH. The common S^S-dithiolate ligand provides stability, while the rigidity effect of other ligands (DPPE (3) > DPPF (2) > PPh3 (1)) regulates the formation of the transition state, resulting in the NiIII-H intermediate in the order of 1 > 2 > 3. The foot-of-the-wave analysis supports the widely accepted ECEC mechanism for Ni-based complexes with the first protonation step as a rate-determining step. The electrocatalytic proton reduction activity follows in the order of complex 1 > 2 > 3. The comparatively lower overpotential and higher turnover frequency of complex 1 are attributed to the flexibility of the PPh3 ligand, which favours the easy formation of a transition state.

Origin of electrocatalytic nitrogen reduction activity over transition metal disulfides: critical role of in situ generation of S vacancy

We identified an interesting electrochemistry-driven “in situ” generation of S-vacancies of transition metal disulfides, which serves as an origin of promising electrochemical ammonia synthesis activity.

A post-modification strategy to precisely construct dual-atom sites for oxygen reduction electrocatalysis

Dual-atom catalysts (DACs) afford promising potential for oxygen reduction electrocatalysis due to their high atomic efficiency and high intrinsic activity. However, precise construction of dual-atom sites remains a challenge. In this work, a post-modification strategy is proposed to precisely fabricate DACs for oxygen reduction electrocatalysis. Concretely, a secondary metal precursor is introduced to the primary single-atom sites to introduce direct metal–metal interaction, which ensures the formation of desired atom pair structure during the subsequent pyrolysis process and allows for successful construction of DACs. The as-prepared FeCo-NC DAC exhibits superior oxygen reduction electrocatalytic activity with a half-wave potential of 0.91 V vs. reversible hydrogen electrode. Zn–air batteries equipped with the FeCo-NC DAC demonstrate higher peak power density than those with the Pt/C benchmark. More importantly, this post-modification strategy is demonstrated universal to achieve a variety of dual-atom sites. This work presents an effective synthesis methodology for precise construction of catalytic materials and propels their applications in energy-related devices.

Fabrication of NiSx/MoS2 interface for accelerated charge transfer with greatly improved electrocatalytic activity in nitrogen reduction to produce ammonia

Electrocatalytic reduction of dinitrogen to produce ammonia at ambient conditions has increasingly attracted attentions. Molybdenum sulfide (MoS2) exhibits promises in electrocatalysis. However, the lack of reactive sites significantly limited the electrocatalytic activity of MoS2 when applied in the reduction of N2 to produce ammonia. Herein, we successfully prepared a NiSx/MoS2 heterostructural composite with abundant interfaces exposed. Moreover, the presence of metallic phase 1T-MoS2 provided better conductivity and more active sites. Benefited from this interface design, as-prepared NiSx/MoS2 composites exhibited excellent electrocatalytic activity in reduction of N2. The ammonia yield rate reached as high as 68.78 µg h−1 mg−1cat. at −0.60 V (vs. RHE) with a Faradic efficiency of 48.53 % at −0.50 V (vs. RHE), as well as charming selectivity and long-term stability. The density functional theory (DFT) calculation results indicated that the heterointerface formed between NiSx/MoS2 composites facilitated electrons transfer. And the adsorption of N2 on the Mo site is more stable, which synergistically improves the NRR performance. This work provides new evidences of constructing heterojunction materials to accelerate electron transfer between interfaces for highly efficient electrocatalytic nitrogen reduction.

Molecular Recognition Regulates Coordination Structure of Single‐Atom Sites

AbstractCoordination engineering for single‐atom sites has drawn increasing attention, yet its chemical synthesis remains a tough issue, especially for tailorable coordination structures. Herein, a molecular recognition strategy is proposed to fabricate single‐atom sites with regulable local coordination structures. Specifically, a heteroatom‐containing ligand serves as the guest molecule to induce coordination interaction with the metal‐containing host, precisely settling the heteroatoms into the local structure of single‐atom sites. As a proof of concept, thiophene is selected as the guest molecule, and sulfur atoms are successfully introduced into the local coordination structure of iron single‐atom sites. Ultrahigh oxygen reduction electrocatalytic activity is achieved with a half‐wave potential of 0.93 V versus reversible hydrogen electrode. Furthermore, the strategy possesses excellent universality towards diversified types of single‐atom sites. This work makes breakthroughs in the fabrication of single‐atom sites and affords new opportunities in structural regulation at the atomic level.

Molecular Recognition Regulates Coordination Structure of Single-Atom Sites.

Coordination engineering for single-atom sites has drawn increasing attention, yet its chemical synthesis remains a tough issue, especially for tailorable coordination structures. Herein, a molecular recognition strategy is proposed to fabricate single-atom sites with regulable local coordination structures. Specifically, a heteroatom-containing ligand serves as the guest molecule to induce coordination interaction with the metal-containing host, precisely settling the heteroatoms into the local structure of single-atom sites. As a proof of concept, thiophene is selected as the guest molecule, and sulfur atoms are successfully introduced into the local coordination structure of iron single-atom sites. Ultrahigh oxygen reduction electrocatalytic activity is achieved with a half-wave potential of 0.93 V versus reversible hydrogen electrode. Furthermore, the strategy possesses excellent universality towards diversified types of single-atom sites. This work makes breakthroughs in the fabrication of single-atom sites and affords new opportunities in structural regulation at the atomic level.

Halloysite nanotubes-loaded conductive polymer as substrate and label material for sensitive detection of amyloid-β protein by electrochemical immunosensor

Amyloid-beta protein (Aβ) is a unique biomarker for Alzheimer's disease (AD). The sandwich-type electrochemical immunosensor, one of the key tools for detecting biomarkers, relies on a high-performance signal amplification approach to enhance its sensitivity. Ni/PdH nanodendrites (Ni/PdH NDs) have increased catalytic activity due to their unique interaction with palladium hydride and their nickel-rich surface, tunable shape and high specific surface area. Modified halloysite nanotubes (mHNT)-loaded with polypyrrole (PPy@mHNT) possess excellent dispersion and a large surface area. This enables the formation of a conductive network to prevent the accumulation of Ni/PdH NDs. Additionally, it exposes more electrocatalytic active centers, effectively amplifying electrical signals. By utilizing Ni/PdH@PPy@mHNT as the labeling material, it shows a consistent and remarkable electrocatalytic activity in H2O2 reduction, leading to signal amplification. The acid-etched HNT coated with polyaniline (PANI@eHNT) exhibits an exceptionally low background signal and outstanding conductivity. This not only accelerates electron transfer on the electrode surface, but also ensures the stable incubation of biomolecules post-amino grafting. Utilizing NH2-PANI@eHNT as a substrate material can guarantee stable biomolecule incubation, offer a stable sensing platform and enhance immunosensor performance. The signal can be amplified and the immunosensor's sensitivity can be raised through the efficient cooperation of the aforementioned nanomaterials. Under optimum circumstances, the electrochemical immunosensor had the lowest detection limit of 5.53 fg mL−1 and a linear range of 50 fg mL−1 to 100 ng mL−1. Based on the outstanding performance previously mentioned, this immunosensor is anticipated to aid in the early detection of AD.

Electrochemical investigation on calcium ion sensing and steady-state diffusion analysis using zinc oxide modified glassy carbon electrode

The concentration of calcium ions in human blood serum typically falls within a narrow range of 2 and 2.5 mmol/L. However, hyperthyroidism, resulting from an overactive parathyroid gland, can lead to an elevation of calcium ion concentration beyond 2.5 mmol/L, necessitating the development of a highly sensitive and selective electrochemical sensor for calcium ion detection. To address this issue, a highly sensitive and selective electrochemical sensor based on zinc oxide nanoparticles-chitosan composite modified glassy carbon electrode (GC/ZnO-Chitosan) was fabricated for the detection of calcium ions. Cyclic voltammetric analysis revealed that the fabricated electrode possesses excellent electrocatalytic activity for calcium ion oxidation and reduction. The fabricated electrode showed high sensitivity (449.887 µA mM−1) towards calcium ions over the wide detection range of 2.14–3.5 mM with a low detection limit of 2.26 µM, and a low quantification limit of 7.45 µM. Moreover, the fabricated electrode showed fast response time (<25 s) due to the synergistic effect of enhanced adsorption of calcium ions (Γ=2.17×10-7 mol cm−2), efficient electron shuttling capacity of ZnO nanoparticles between GCE (ks=6.01 s−1) and the adsorbed calcium ions, and enhanced diffusion of calcium ions (DCa2+=1.2788×10-6cm2s-1) within the ZnO-Chitosan composite film. Genocchi polynomial approximation method was employed for the establishment of a precise mathematical relationship between the steady-state concentration of calcium ions and the distance from the electrode's surface. This newly developed GC/ZnO-Chitosan electrode presents a significant improvement over previously developed electrodes for calcium ions, as it enables the precise analysis of calcium ion diffusion profiles at steady-state.