Evolution Of Ammonia Research Articles

Isocyanide Ligation Enables Electrochemical Ammonia Formation in a Synthetic Cycle for N2 Fixation.

Transition-metal-mediated splitting of N2 to form metal nitride complexes could constitute a key step in electrocatalytic nitrogen fixation, if these nitrides can be electrochemically reduced to ammonia under mild conditions. The envisioned nitrogen fixation cycle involves several steps: N2 binding to form a dinuclear end-on bridging complex with appropriate electronic structure to cleave the N2 bridge followed by proton/electron transfer to release ammonia and bind another molecule of N2. The nitride reduction and N2 splitting steps in this cycle have differing electronic demands that a catalyst must satisfy. Rhenium systems have had limited success in meeting these demands, and studying them offers an opportunity to learn strategies for modulating reactivity. Here, we report a rhenium system in which the pincer supporting ligand is supplemented by an isocyanide ligand that can accept electron density, facilitating reduction and enabling the protonation/reduction of the nitride to ammonia under mild electrochemical conditions. The incorporation of isocyanide raises the N-H bond dissociation free energy of the first N-H bond by 10 kcal/mol, breaking the usual compensation between pKa and redox potential; this is attributed to the separation of the protonation site (nitride) and the reduction site (delocalized between Re and isocyanide). Ammonia evolution is accompanied by formation of a terminal N2 complex, which can be oxidized to yield bridging N2 complexes including a rare mixed-valent complex. These rhenium species define the steps in a synthetic cycle that converts N2 to NH3 through an electrochemical N2 splitting pathway, and show the utility of a second, tunable supporting ligand for enhancing nitride reactivity.

Atomically‐Scattered Active Centers Accelerating Photocatalytic Evolution of Ammonia

AbstractPhotocatalytic N2 reduction to ammonia rises as a cost‐effective, environmentally benign, and efficient route to generate ammonia as a transportable/storable energy carrier and essential fertilizer. Recently, photocatalysts anchored with various atomically scattered active centers (ASACs), such as Ru, Fe, Au, Pt, Cu, Mo, and La, are extensively explored in photocatalytic N2‐to‐ammonia transformation. This review critically summarizes the current achievements in the synthesis of various photocatalyst supports (such as metal oxide, carbon nitride, metal‐organic framework, and covalent organic framework) anchored with the above‐mentioned ASACs for N2 reduction to form ammonia. The synthesis routes, structural/compositional characteristics, and performances of these ASACs anchored photocatalysts are summarized and introduced. Furthermore, the atomic‐scale relationship between the structure/composition and performance of these ASACs anchored photocatalysts is also introduced. The reaction mechanism including the reaction kinetics/thermodynamics, reaction pathways, and charge carrier kinetics, especially those revealed by various state‐of‐art characterization techniques, have been highlighted. This review also outlines the basic principles for the synthesis of novel photocatalysts aimed at ammonia evolution. Finally, the current challenges, opportunities, and future outlooks of ASACs anchored photocatalysts for ammonia evolution are introduced.

Bimetallic NH2-MIL-101(Fe, Co) as highly efficient photocatalyst for nitrogen fixation

Developing effective catalysts for N2 photofixation at ambient conditions is highly desirable but still challenging. Herein, we reported a novel Co-doped NH2-MIL-101(Fe) (NM-Fe) bimetallic organic framework (BMOF) for visible-light-driven catalytic N2 fixation. It was found that the doping of Co ions could effectively enhance light-harvesting, reduce the conduction band potential, suppress the recombination of photogenerated carriers, and promote the activation of N2. Consequently, the photocatalytic N2 reduction efficiency of bimetallic NH2-MIL-101(Fe, Co) (NM-Fe-Co) was obviously boosted. The sample with the optical Co/Fe molar ratio of 0.15, namely NM-Fe-0.15Co, enabled an ammonia evolution rate up to 335.7 µmol g−1 h−1 without the aid of any sacrificial agents, a 4.4-fold increase over the monometallic NM-Fe baseline. Additionally, the bimetallic NM-Fe-Co displayed excellent stability. The possible reaction mechanism of nitrogen fixation over NM-Fe-Co was proposed based on in-situ infrared analysis. Our study demonstrates a promising strategy for designing potent MOF-based catalysts for N2 photofixation.

Ligand bridged MXene/metal organic frameworks heterojunction for efficient photocatalytic ammonia synthesis

Efficient interfacial charge transfer is imperative for enhancing N2 photofixation, yet controlling this process proves challenging. Herein, a unique ligand pre-coupling strategy was employed to design ligand-bridged MXene/MIL-125(Ti), creating a coordination bond between Ti3C2Ox and MIL-125(Ti) and forming a ligand-bridge, aiming to regulate interfacial electron transfer. Kelvin probe force microscopy and charge density difference analysis revealed the establishment of an electronic unidirectional transport channel from MIL-125(Ti) to Ti3C2Ox through this ligand-bridge. This effectively reduced the interface charge transfer resistance, enhanced the separation efficiency of charge carriers. Consequently, the Ti3C2Ox/MIL-125(Ti) manifested an excellent ammonia evolution rate of 103.02 μmol·gcat-1·h-1. Furthermore, the efficiency of this strategy for accelerating the separation of photogenerated carriers was demonstrated in five other MOFs, demonstrating its potential for constructing ligand-bridged MXene/MOFs heterojunctions.

Cu-Catalyzed, electron-relayed three-component synthesis of 2-alkenylbenzothiazoles with cathodic ammonia evolution

A CuI-catalyzed, one-pot, three-component reaction of benzaldehydes, 2-aminobenzothiol and malononitrile is described, wherein CuI plays an electron relay. The method features simplified operation, highly atom economy, and mild reaction conditions.

Efficient photofixation of nitrogen to ammonia over an S-scheme-based NiSnO3-g-C3N4 heterojunction

A limited injection of photogenerated electrons in N2 molecules is the core problem limiting the performance of heterojunction materials in photofixing N2 to ammonia. In this study, an inexpensive Sn-based perovskite (NiSnO3, NSO) was anchored over the g-C3N4 (gCN) sheets under mild reaction conditions to develop an S-scheme heterojunction for the photocatalytic nitrogen reduction reaction. The NSO-gCN heterojunction, utilizing methanol as a sacrificial agent, showed remarkable N2 reduction capability with an impressive ammonia evolution of 566 µmolg−1h−1, surpassing that of gCN and NSO by the factor of 3.6 and 40, respectively, in visible light. The significantly improved performance of the material was attributed to the S-scheme charge transfer mechanism. The NSO-gCN photocatalyst showed good stability with only a marginal decrease measured in the activity over 3 cycles of the photocatalytic reaction. The study reveals a new strategy to design the highly efficient S-scheme-based heterojunctions by using Sn-based perovskite for sustainable ammonia synthesis.

D-band center modulation of B-mediated FeS2 to activate molecular nitrogen for electrocatalytic ammonia synthesis

Electrocatalytic nitrogen fixation is a promising approach for ambient ammonia synthesis. The key that limits the improvement of ammonia evolution performance is the NN bond cleavage of molecular nitrogen. One effective route to break this bottleneck is the d-band center modulation of catalysts. Herein, a nonmetal boron mediated FeS2 (B-FeS2) is developed for electrocatalytic nitrogen fixation. The B-mediation alters the spin-orbits of Fe site and upshifts the d-band center of FeS2, thus inducing a strong d-π* interaction between the Fe site and nitrogen to activate NN bond. Besides, the experimental and theoretical calculations indicate the B-mediation reduces the energy barrier for *NNH intermediate, thus significantly accelerating ammonia production. As a result, B-FeS2 displays high ammonia yield (1.56 mmol·g−1·h−1) with 12.6 % Faradaic efficiency. This strategy of d-band center tuning induced by the B-mediation provides a distinctive insight for the design of high-efficiency electrocatalysts.

In situ fabrication of N-doped Ti3C2Tx-MXene-modified BiOBr Schottky heterojunction with high photoelectron separation efficiency for enhanced photocatalytic ammonia synthesis

NH3 synthesis under ambient conditions remained great challenge owing to the strong NN bond energy, high ionization energy, and poor proton affinity of NH3. Herein, dopamine hydrochloride was selected as a N doping source to in-situ polymerization on the Ti3C2Tx MXenes surface forming a highly efficient co-catalyst, and then integrated into BiOBr to induce a super high photocatalysis for ammonia synthesis. As expected, BiOBr was evenly dispersed on the N-Ti3C2Tx MXene surface. The photocatalysis possessed a high degree of photocatalytic ammonia evolution (270.73 μmol/g·h and 3.27 times higher than that of BiOBr) and retained about 60 % of its ammonia evolution after five consecutive cycles. The photocatalyst mechanism is high dispersion and elevated conduction band potential of N-Ti3C2Tx MXene nanosheets facilitated charge transfer to the active sites of the nanosheets. This study proved the potential use of dopamine hydrochloride in MXene photocatalytic materials for solar energy utilization ammonia synthesis.

Oxygen defect modulating the charge behavior in titanium dioxide for boosting photocatalytic nitrogen fixation performance

Extremely high-temperature and high-pressure requirement of Haber-Bosch process motivates the search for a sustainable ammonia synthesis approach under mild conditions. Photocatalytic technology is a potential solution to convert N2 to ammonia. However, the poor light absorption and low charge carrier separation efficiency in conventional semiconductors are bottlenecks for the application of this technology. Herein, a facile synthesis of anatase TiO2 nanosheets with an abundance of surface oxygen vacancies (TiO2-OV) via the calcination treatment was reported. Photocatalytic experiments of the prepared anatase TiO2 samples showed that TiO2-OV nanosheets exhibited remarkably increased ammonia yield for solar-driven N2 fixation in pure water, without adding any sacrificial agents. EPR, XPS, XRD, UV-Vis DRS, TEM, Raman, and PL techniques were employed to systematically explore the possible enhanced mechanism. Studies revealed that the introduced surface oxygen vacancies significantly extended the light absorption capability in the visible region, decreased the adsorption and activation barriers of inert N2, and improved the separation and transfer efficiency of the photogenerated electron-hole pairs. Thus, a high rate of ammonia evolution in TiO2-OV was realized. This work offers a promising and sustainable approach for the efficient artificial photosynthesis of ammonia.

Tuning the Interfaces of ZnO/ZnCr2 O4 Derived from Layered-Double-Hydroxide Precursors to Advance Nitrogen Photofixation.

Drawing inspiration from the enzyme nitrogenase in nature, researchers are increasingly delving into semiconductor photocatalytic nitrogen fixation due to its similar surface catalytic processes. Herein, we reported a facile and efficient approach to achieving the regulation of ZnO/ZnCr2 O4 photocatalysts with ZnCr-layered double hydroxide (ZnCr-LDH) as precursors. By optimizing the composition ratio of Zn/Cr in ZnCr-LDH to tune interfaces, we can achieve an enhanced nitrogen photofixation performance (an ammonia evolution rate of 31.7 μmol g-1 h-1 using pure water as a proton source) under ambient conditions. Further, photo-electrochemical measurements and transient surface photovoltage spectroscopy revealed that the enhanced photocatalytic activity can be ascribed to the effective carrier separation efficiency, originating from the abundant composite interfaces. This work further demonstrated a promising and viable strategy for the synthesis of nanocomposite photocatalysts for nitrogen photofixation and other challenging photocatalytic reactions.

Construction of the multi-layer TiO2-NTs/Sb-SnO2/PbO2 electrode for the highly efficient and selective oxidation of ammonia in aqueous solution: Characterization, performance and mechanism

Electrochemical oxidation is a promising technology to convert ammonia nitrogen to environmental-friendly gaseous nitrogen, but the high cost of the precious metal as an electrode limits its application. Herein, the multi-layer TiO2-NTs/Sb-SnO2/PbO2 electrode, a cheap and efficient dimensionally stable anode (DSA), was constructed for selective electrocatalytic oxidation of ammonia. The surface morphology, crystalline structure, and composition of the TiO2-NTs/Sb-SnO2/PbO2 electrode were investigated by the field emission scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The synergistic effect of the multi-layer structures of the electrode contributed to a stable structure and efficient electrocatalytic activity. Accelerated lifetime measurements and electrode recycling tests proved that the electrode possessed outstanding stability and long life with continuously used for 935 h. Compared with the commercial Ti/RuO2-IrO2, the TiO2-NTs/Sb-SnO2/PbO2 electrode displayed a more excellent performance of chlorine evolution and higher removal efficiency of ammonia. Under the optimal conditions, 30 mg/L of ammonia nitrogen could be completely removed with 92.3% selective conversion to gaseous nitrogen after 60 min. Moreover, the difference between oxygen evolution potential and chlorine evolution potential exceeded 0.45 V on the TiO2-NTs/Sb-SnO2/PbO2 electrode, which enhanced the anodic chlorine evolution reaction. Hypochlorite radical (ClO•) was supposed as the dominant oxidant to transform ammonia in water, which could promote ammonia removal and the selectivity of gaseous nitrogen with minimizing by-products formation such as nitrite and nitrate, etc. Therefore, this study suggests that the constructed multi-layer TiO2-NTs/Sb-SnO2/PbO2 electrode might be a promising anode for the electrochemical oxidation of ammonia nitrogen to N2 in an aqueous solution.

Bio-inspired citric acid-based bimetallic photocatalyst for nitrogen fixation from air under ambient conditions

Discovery of effective materials for photocatalytic nitrogen fixation under ambient conditions provides new opportunities for sustainable futures. Nitrogenase provides the best example of environmentally friendly nitrogen reduction. Inspired by homocitrate's specific activating effect on nitrogenase, citric acid was used instead of homocitric acid to prepare citric acid-based bimetallic organic frameworks (MOFs). Metals such as cerium and copper as bimetallic centers were coordinated with citric acid to mimic FeMo bimetallic active center in the M cluster. The results show that the morphology, structure and photocatalytic activity of the catalysts has been significantly affected by the amount of citric acid. The molar ratio of total metal to citric acid of 1.5:20 had the best ammonia evolution rate from air at a normal temperature and pressure (NTP), which was as high as 1027.6 μg g−1 h−1. It was further confirmed by the numerically study of the interactions between light and the synthesized photocatalytic particles, which can be intuitively seen that CeCu@CA-20 can support more surface charges. This work provides an effective strategy for citrate-based MOF photocatalysts and offers a new idea for nitrogenase biomimetics.

Highly distributed amorphous copper catalyst for efficient ammonia electrosynthesis from nitrate

Electroreduction of nitrate to ammonia, instead of N2, is beneficial toward pollution control and value-added chemical production. Metallic catalysts have been developed for enhancing ammonia evolution efficiency from nitrate based on the crystalline state of the catalyst. However, the development of amorphous metallic catalysts with more active sites is still unexplored. Herein, a highly distributed amorphous Cu catalyst exhibiting an outstanding ammonia yield rate of 1.42 mol h−1 g−1 and Faradaic efficiency of 95.7%, much superior to crystallized Cu, is demonstrated for nitrate-reduction to ammonia. Experimental and computational results reveal that amorphizing Cu increases the number of catalytic sites, enhances the NO3− adsorption strength with flat adsorption configurations, and facilitates the potential determining step of *NO protonation to *NHO. The amorphous Cu catalyst shows good electrochemical stability at − 0.3 V, while crystallization weakens the activity at a more negative potential. This study confirms the crystallinity-activity relationship of amorphous catalysts and unveils their potential-limited electrochemical stability.

Construction of 2D up-conversion calcium copper silicate nanosheet for efficient photocatalytic nitrogen fixation under full spectrum

Using clean and renewable solar energy to convert nitrogen to ammonia is promising, however the low utilization of light and the high cost of catalyst restrain its application. Herein, novel two-dimensional(2D) silicate CaCuSi 4 O 10 nanosheet was prepared by high-temperature solid state method using silica derived from palygorskite clay (Pal) and calcium carbonate derived from egg shells, respectively. The photocatalytic nitrogen fixation was performed using CaCuSi 4 O 10 compound as catalyst. The effect of flux content on the ammonia generation rate was investigated. Results demonstrated that the 2D CaCuSi 4 O 10 nanosheet can chemically adsorb and activate N 2 due to the high surface area along with abundant oxygen vacancies. The ammonia evolution rate of CaCuSi 4 O 10 can reach up to 60.3 μmol·g −1 ·h −1 and 15.6 μmol·g −1 ·h −1 under simulated solar light and near infrared (NIR) light irradiation, respectively. The enhanced photocatalytic nitrogen fixation can be ascribed to the up-conversion capability of CaCuSi 4 O 10 , which converts NIR into visible and UV light improving the utilization efficiency of full solar spectrum. Current study may offer a promising strategy for cost-effective photocatalytic nitrogen fixation under full spectrum. • 2D silicate CaCuSi 4 O 10 nanosheet prepared using mineral and biomass. • CaCuSi 4 O 10 compound owned abundant oxygen vacancies favoring N 2 activation. • Up-conversion capability of CaCuSi 4 O 10 improved solar energy utilization. • CaCuSi 4 O 10 nanosheet demonstrated cost-effective photocatalytic nitrogen fixation.

Two-Dimensional Defective Boron-Doped Niobic Acid Nanosheets for Robust Nitrogen Photofixation.

Direct nitrogen photofixation is a feasible solution toward sustainable production of ammonia under mild conditions. However, the generation of active sites for solar-dirven nitrogen fixation not only limits the fundamental understanding of the relationship among light absorption, charge transfer, and catalytic efficiency but also influences the photocatalytic activity. Herein, we report two-dimensional boron-doped niobic acid nanosheets with oxygen vacancies (B-Vo-HNbO3 NSs) for efficient N2 photofixation in the absence of any scavengers and cocatalysts. Impressively, B-Vo-HNbO3 NS as a model catalyst achieves the enhanced ammonia evolution rate of 170 μmol gcat-1 h-1 in pure water under visible-light irradiation. The doublet coupling representing 15NH4+ in an isotopic labeling experiment and in situ infrared spectra confirm the reliable ammonia generation. The experimental analysis and density functional theory (DFT) calculations indicate that the strong synergy of boron dopant and oxygen vacancy regulates band structure of niobic acid, facilitates photogenerated charge transfer, reduces free energy barriers, accelerates reaction kinetics, and promotes the high rates of ammonia evolution. This work provides a general strategy to design active photocatalysts toward solar N2 conversion.

Diurnal evolution of total column and surface atmospheric ammonia in the megacity of Paris, France, during an intense springtime pollution episode

Abstract. Ammonia (NH3) is a key precursor for the formation of atmospheric secondary inorganic particles, such as ammonium nitrate and sulfate. Although the chemical processes associated with the gas-to-particle conversion are well known, atmospheric concentrations of gaseous ammonia are still scarcely characterized. However, this information is critical, especially for processes concerning the equilibrium between ammonia and ammonium nitrate, due to the semivolatile character of the latter. This study presents an analysis of the diurnal cycle of atmospheric ammonia during a pollution event over the Paris megacity region in spring 2012 (5 d in late March 2012). Our objective is to analyze the link between the diurnal evolution of surface NH3 concentrations and its integrated column abundance, meteorological variables and relevant chemical species involved in gas–particle partitioning. For this, we implement an original approach based on the combined use of surface and total column ammonia measurements. These last ones are derived from ground-based remote sensing measurements performed by the Observations of the Atmosphere by Solar Infrared Spectroscopy (OASIS) Fourier transform infrared observatory at an urban site over the southeastern suburbs of the Paris megacity. This analysis considers the following meteorological variables and processes relevant to the ammonia pollution event: temperature, relative humidity, wind speed and direction, and the atmospheric boundary layer height (as indicator of vertical dilution during its diurnal development). Moreover, we study the partitioning between ammonia and ammonium particles from concomitant measurements of total particulate matter (PM) and ammonium (NH4+) concentrations at the surface. We identify the origin of the pollution event as local emissions at the beginning of the analyzed period and advection of pollution from Benelux and western Germany by the end. Our results show a clearly different diurnal behavior of atmospheric ammonia concentrations at the surface and those vertically integrated over the total atmospheric column. Surface concentrations remain relatively stable during the day, while total column abundances show a minimum value in the morning and rise steadily to reach a relative maximum in the late afternoon during each day of the spring pollution event. These differences are mainly explained by vertical mixing within the boundary layer, provided that this last one is considered well mixed and therefore homogeneous in ammonia concentrations. This is suggested by ground-based measurements of vertical profiles of aerosol backscatter, used as tracer of the vertical distribution of pollutants in the atmospheric boundary layer. Indeed, the afternoon enhancement of ammonia clearly seen by OASIS for the whole atmospheric column is barely depicted by surface concentrations, as the surface concentrations are strongly affected by vertical dilution within the rising boundary layer. Moreover, the concomitant occurrence of a decrease in ammonium particle concentrations and an increase in gaseous ammonia abundance suggests the volatilization of particles for forming ammonia. Furthermore, surface observations may also suggest nighttime formation of ammonium particles from gas-to-particle conversion, for relative humidity levels higher than the deliquescence point of ammonium nitrate.

Atomic-level insights into the activation of nitrogen via hydrogen-bond interaction toward nitrogen photofixation

Summary As the activation of N2 molecules is generally regarded as the bottleneck in N2 reduction, it is of significant importance to develop promising strategies to efficiently activate N2 molecules. Herein, we discovered an innovative approach to activate N2 molecules via hydrogen-bond interaction in N2 photofixation. Porous Cu with surface modification of S atoms (3%-S/Cu) exhibited remarkable catalytic activity and stability in N2 photofixation. Further mechanistic studies revealed that surface S atoms directly participated in the catalytic process by accepting and donating H atoms. In addition, the forming S–H bond significantly promoted the activation of N2 molecules via hydrogen-bond interaction, contributing to the enhanced catalytic activity.

Metal-Organic Framework Membranes Encapsulating Gold Nanoparticles for Direct Plasmonic Photocatalytic Nitrogen Fixation.

Photocatalytic nitrogen fixation reaction can harvest the solar energy to convert the abundant but inert N2 into NH3. Here, utilizing metal-organic framework (MOF) membranes as the ideal assembly of nanoreactors to disperse and confine gold nanoparticles (AuNPs), we realize the direct plasmonic photocatalytic nitrogen fixation under ambient conditions. Upon visible irradiation, the hot electrons generated on the AuNPs can be directly injected into the N2 molecules adsorbed on Au surfaces. Such N2 molecules can be additionally activated by the strong but evanescently localized surface plasmon resonance field, resulting in a supralinear intensity dependence of the ammonia evolution rate with much higher apparent quantum efficiency and lower apparent activation energy under stronger irradiation. Moreover, the gas-permeable Au@MOF membranes, consisting of numerous interconnected nanoreactors, can ensure the dispersity and stability of AuNPs, further facilitate the mass transfer of N2 molecules and (hydrated) protons, and boost the plasmonic photocatalytic reactions at the designed gas-membrane-solution interface. As a result, an ammonia evolution rate of 18.9 mmol gAu-1 h-1 was achieved under visible light (>400 nm, 100 mW cm-2) with an apparent quantum efficiency of 1.54% at 520 nm.

Understanding the key role of vanadium in p-type BiVO4 for photoelectrochemical N2 fixation

The photoelectrochemical N2 reduction reaction (PEC NRR) is extremely charming to the synthetic ammonia (NH3), for its mild operating conditions and low carbon footprint. Taking account of the strong chemical inertness of N2 and competitive hydrogen evolution reaction, it is necessary to explore a robust and stable photoelectrocatalyst. Herein, a robust p-type BiVO4 (p-BiVO4) photocathode is firstly reported for NRR under ambient conditions. Interestingly, V sites are proved as the mainly ideal active center for N2 adsorption/activation based on the density functional theory (DFT) calculations. The ammonia evolution rate (VNH3:11.6 × 10−8 mol h−1 cm−2) and Faradaic efficiency (16.2%) were obtained at −0.1 V vs. RHE in 0.1 M Li2SO4 solution, outperforming most of the photoelectrocatalysts reported thus far. Moreover, the 1H nuclear magnetic resonance result confirmed that the source of N was completely from the feeding N2 gas. This work provided a new opportunity to tap the V-based photocathode in the field of PEC NRR.

Simultaneous detection of trace Pb(II), Cd(II) and Hg(II) by anodic stripping analyses with glassy carbon electrode modified by solid phase synthesized iron-aluminate nano particles

This paper presents an ultrasensitive simultaneous detection procedure for heavy metals (HMs) namely lead; Pb(II), cadmium; Cd(II) and mercury; Hg(II). A bimetallic iron-aluminate (Fe-Al) mixed metal-oxide nano-composite (MMON) on glassy carbon electrode was synthesized using novel solid phase synthesis method. An ammonium ion exchange reaction in solid reagent with simultaneous ammonia evolution produced unique rod-shaped Fe-Al MMON without any solvent addition. The chitosan-mediated electrode (Ch-MMON/GCE) was used to simultaneously detect three most harmful HMs using three anodic stripping techniques namely, cyclic voltammetry (CV), linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV). Three distinct stripping peaks were obtained with concentrations in parts per trillion (ppt) using each of these methods using acetate buffer (0.1 M, pH = 4.5). Obtained LODs for Cd(II), Pb(II), and Hg(II), being 1.678 ppt, 0.301 ppt and 0.658 ppt, respectively by CV whereas LSV gave 1.791 ppt, 0.798 ppt and 2.205 ppt respectively DPV yielded 0.068 ppt, 0.034 ppt and 0.053 ppt, respectively. As observed, DPV was found to be the most sensitive method even though all LOD values were well below the drinking water permissible limits stipulated by WHO. Possible mechanism of ultrasensitive HM detection by the Ch-MMON/GCE was discussed. The modified electrode was successfully used to measure HMs present in water of river Ganges water eliciting significant performance and reliability.