Electrocatalytic Behavior Research Articles

In Situ Synthesis of Co3O4 Nanoparticles on N-Doped Biochar as High-Performance Oxygen Reduction Reaction Electrocatalysts

The development of sustainable and high-performance oxygen reduction reaction (ORR) electrocatalysts is fundamental to fuel cell implementation. Non-precious transition metal oxides present interesting electrocatalytic behavior, and their incorporation into N-doped carbon supports leads to excellent ORR performance. Herein, we prepared a shrimp shell-derived biochar (CC), which was doped with nitrogen via a ball milling approach (N-CC), and then used as support for Co3O4 nanoparticles growth (N-CC@Co3O4). Co3O4 loading was optimized using three different amounts of cobalt precursor: 1.56, 2.33 and 3.11 mmol in N-CC@Co3O4_1, N-CC@Co3O4_2 and N-CC@Co3O4_3, respectively. Interestingly, all prepared electrocatalysts, including the initial biochar CC, presented electrocatalytic activity towards ORR. Both N-doping and the introduction of Co3O4 NPs had a significant positive effect on ORR performance. Meanwhile, the three composites showed distinct ORR behavior, demonstrating that it is possible to tune their electrocatalytic performance by changing the Co3O4 loading. Overall, N-CC@Co3O4_2 achieved the most promising ORR results, displaying an Eonset of 0.84 V vs. RHE, jL of −3.45 mA cm−2 and excellent selectivity for the 4-electron reduction (n = 3.50), besides good long-term stability. These results were explained by a combination of high content of pyridinic-N and graphitic-N, high ratio of pyridinic-N/graphitic-N, and optimized Co3O4 loading interacting synergistically with the porous N-CC support.

Sensitive and Fast Simultaneous Voltammetric Determination of Dopamine and Uric Acid Using Simple Screen‐Printed Carbon Electrode Without Pretreatment and Modification

A simple, commercially available, unmodified screen‐printed carbon electrode (SPCE) was investigated for the simultaneous voltammetric determination of dopamine (D/A) and uric acid (U/A) in a medium of very low concentration of supporting electrolyte for the first time. The ordinary, simple SPCE from DropSens (DS‐SPCE) was found to be able to separate the overlapping peaks of D/A and U/A with a wide peak potential separation of 300 mV in a medium of very low concentration (0.001 M) of NaH2PO4 as supporting electrolyte (buffer of low capacity) at pH 8.0. Medium of low concentration of electrolyte made it possible to expose the bare electrode surface for its high catalytic activity which resulted into a high peak current signals, particularly for D/A. The DS‐SPCE showed excellent electrocatalytic performance than the other SPCE. The effect of electrolyte concentration and pH on the electrocatalytic behavior of electrode were thoroughly discussed. The DS‐SPCE displayed a sensitive results in good linear ranges from 0.1–5 to 6–20 µM for D/A and 0.5–41.5 µM for U/A. The disposable electrode demonstrated better discrimination ability toward the detection of D/A and U/A over ascorbic acid and other potential interfering species. Moreover, the sensor presented sensitive and highly accurate results in human urine samples without preliminary treatment. The DS‐SPCE sensor was found to be simple, efficient, fast, low cost, and greener than the other reported modified sensors, while providing better sensitivities to detect D/A and U/A simultaneously. Thus, the bare, unmodified DS‐SPCE can be a convenient sensing device for the routine analysis of D/A and U/A, without requiring any complex pretreatment and modification steps of the electrode.

Electrocatalytic activity of sodium copper pectates in oxygen reduction reaction in fuel cells

In this paper, the results of the electrocatalytic behavior of a series of copper sodium pectate complexes with different Cu2+ contents (5, 10, 15, 20, 25%) towards the oxygen reduction reaction (ORR) are presented. To investigate the catalytic activity of the studied complexes in ORR, the cyclic voltammograms (CVA) recorded in an oxygen-saturated environment and inert argon gas were compared. Clear reduction peaks are observed in the CVA, confirming the electrochemical activity of the complexes in the oxygen reduction reaction. The kinetics and mechanism of the oxygen reduction reaction on the glassy carbon modified with the complexes in an acidic 0.5 M H2SO4 medium were analyzed. The results obtained by cyclic voltammetry at different scan rates show that the ORR on the copper sodium pectate complexes supported on the glassy carbon is diffusion-controlled. The calculation of the number of electrons participating in the electrochemical reaction was carried out. It was found that the best catalyst of the entire series of samples is a sodium pectate complex with a 5% copper content (n = 4). It was noted that the compound is characterized by a large specific surface area. An increase in the amount of copper ions in coordination biopolymers leads to film formation and a decrease in catalytic activity.

Relationships between the Surface Hydrophilicity of a Bismuth Electrode and the Product Selectivity of Electrocatalytic CO2 Reduction.

Two types of bismuth films (micro-Bi and nano-Bi) were prepared, and their electrocatalytic behavior was studied in terms of reduction current and product selectivity in a potential range of -0.776 to -1.376 V vs RHE. CO2 and H2O molecules competed with each other for reduction on the surfaces of both types of films, and formate and H2 were the respective major products of reductive reactions. Under the same conditions, nano-Bi exhibited lower selectivity for formate and higher selectivity for H2 compared to the respective micro-Bi cases with bismuth films of similar thickness. This can be attributed to the higher hydrophilicity of bismuth film surfaces of nano-Bi due to surface nanoscale roughness and lower surface-carbon content compared with those of micro-Bi. Our results suggest a new strategy for controlling the selectivity of electrocatalytic CO2 reduction under aqueous electrolytes through the use of surface engineering.

Interplay Between Calcination Temperature and Alkaline Oxygen Evolution of Electrospun High-Entropy (Cr1/5Mn1/5Fe1/5Co1/5Ni1/5)3O4 Nanofibers.

Spinel-structured transition metal (TM) oxides have shown great potential as a sustainable alternative to platinum group metal-based electrocatalysts. Among them, high-entropy oxides (HEOs) with multiple TM-cation sites are suitable for engineering octahedral redox-active centers to enhance the catalyst reactivity. This paper reports on the preparation of electrospun (Cr1/5Mn1/5Fe1/5Co1/5Ni1/5)3O4 nanofibers (NFs) and their evaluation as electrocatalysts. Its main aim is to unveil the nanostructural features that play a key role in the alkaline oxygen evolution reaction. Differing calcination temperature (300-800°C) and duration (2 or 4h) leads to different morphology of the NFs, crystallinity of the oxide, density of defects, and cation distribution in the lattice, which reflect in different electrocatalytic behaviors. The best performance (overpotential and Tafel slope at 10mAcm-2: 325mV and 40mVdec-1, respectively) pertains to the NFs calcined at 400°C for 2h. To gain a deeper understanding of their electrocatalytic properties, the pristine NFs are investigated by a combination of analytical techniques. In particular, broadband electric spectroscopy reveals that the mobility of oxygen vacancies in the best electrocatalyst is associated to very fast local dielectric relaxations of metal coordination octahedral geometries and experimentally demonstrates the key role of O-deficient octahedra.

Highly enhanced electro-catalytic behavior of an amide functionalized Cu(II) coordination polymer on OER at large current densities

Extensive utilization of fossil fuels has led to their swift exhaustion, causing an escalating energy dilemma and significant environmental apprehensions. This situation has spurred advancement of sustainable energy conversion systems. Electrochemical water splitting is viewed as a capable method for generating hydrogen and oxygen intended for diverse electrochemical energy apparatus. A proficient, multifunctional electro-catalyst capable of facilitating both OERs) and HERs is of paramount importance. In this work, we report Cu-MOF electro-catalyst synthesized via the solvothermal route engaging OER activity using nickel foam (NF) in a 1 M KOH solution. Several analytical techniques were used to investigate the electro-catalysts BET, PXRD, FTIR and oxidation states. The water-splitting evaluation of the LOCOM-1 demonstrated exceptional oxygen activity concerning OER (oxygen evolution reaction), showcasing to extent a current density of 10 mAcm−2 a reduced of 286 mV over potential. Additionally, it exhibited a diminished onset potential of 1.37 V attributable towards a decreased Tafel slope of 44.50 mVdec−1, and a proton couple electron transfer (PCET) channel that is stable over an extended period of time (1000 cycles of cyclic voltammetry and 40 h of chronoamperometry). Therefore, this current endeavour might offer a new prospect or pathway for exploring the OER (Oxygen Evolution Reaction).

Thin-Film Study of Delithiated LiCoO2 Catalyst for Oxygen Evolution Reaction in Alkaline Media

Introduction Renewable energy is indispensable for realizing the sustainable society, and the use of hydrogen energy as an energy carrier is recently gathering attention. It is therefore strongly needed to develop energy conversion devices with the production of hydrogen, and anion-exchange membrane water electrolysis is extensively studied due to its cost effectiveness and relative safety[1]. In these systems, however, sluggish kinetics of oxygen evolution reaction (OER) require large overpotential, which motivates us to explore efficient OER electrocatalysts in alkaline media. Objective Among OER catalysts, LiCoO2 is known as a highly active catalyst in alkaline media. In addition, it has been reported that the catalytic activity of LiCoO2 powder can be improved by delithiation[2]. In order to discuss the electrochemical properties of the delithiated LiCoO2 more in detail, the use of thin-film electrodes is effective because it contains no binder or conductive addictive. Pulsed laser deposition (PLD) method is a favorable method to fabricate thin film electrodes because dense and pinhole-free films can be grown by this method. In this study, we prepared LiCoO2 thin-film electrodes by the PLD method, followed by the electrochemical delithiation of them. Then, their OER activities were evaluated to compare their electrocatalytic behaviors. Experimental LiCoO2 thin films were prepared by PLD. LiCoO2 was deposited on Pt substrate. After preparing the LiCoO2 thin film, it was characterized by X-ray diffraction (XRD) measurement. Electrochemical delithiation of LiCoO2 thin films was conducted by using a three-electrode cell. LiCoO2 thin film grown on Pt substrate was used as a working electrode, and Li metal was used as counter and reference electrodes. A solution of 1 mol dm- 3 LiPF6 in propylene carbonate was used as the electrolyte. The delitiation process was performed by charging the cell at 4.30 V vs. Li+/Li after two charge-discharge cycles between 3.5 V and 4.2 V (vs. Li+/Li). After this process, the resultant delithiated LiCoO2 thin films (referred to as De-LiCoO2 thin-films) were characterized by XRD. Regarding the electrochemical evaluation of the OER activities for De-LiCoO2 thin-film, a three-electrode cell was used. De-LiCoO2 thin film was used as a working electrode, Pt mesh was used as a counter electrode, and Hg/HgO was used as a reference electrode. A solution of 0.1 mol dm- 3 KOH (O2 gas was bubbled for 90 seconds) was used as an electrolyte. Cyclic voltammetry was carried out at a sweep range from 0.2 to 0.8 V (vs. Hg/HgO). The electrode was cycled for 10 times at a scan rate of 10 mV s- 1. Results and Disccusion Figure 1 shows XRD patterns of LiCoO2 and De-LiCoO2. Before delithiation, the XRD pattern was in good agreement with the simulated patterns generated from ICSD database (Number 51182). After the delithiation, the XRD peaks at 2θ ≈ 19° were lowered with an appearance of a new peak at 2θ ≈ 18.4°, suggesting that the LiCoO2 thin film was successfully delithiated by the delithiation process employed in the present study. Comparison of cyclic voltammograms between the LiCoO2 and the De-LiCoO2 thin films is shown in Fig. 2. The LiCoO2 thin film showed larger Co3/4+ peak at around 1.5 V, which is ascribed to both lithium removal into electrolyte and Li ordering within the surface/bulk[3]. On the other hand, the De-LiCoO2 thin film did not show such peaks, implying that lithium content of the as-prepared De-LiCoO2 was much lower than that of the pristine LiCoO2. The De-LiCoO2 showed a different OER activity from that of pristine LiCoO2, implying that the OER activity was dependent upon lithium content of the thin films. The effect of lithium content on the OER activity and its quantitative discussion is under investigation, and details will be discussed in the conference. Reference [1] Stefania Marani, Paolo Salvi, Paolo Nelli, Rachele Pesenti, Marco Villa, Mario Berrettoni, Giovanni Zangari, and Yohannes Kiros., Electrochimica Acta 82, 384-391 (2012).[2] Zhiyi Lu, Haotian Wang, Desheng Kong, Kai Yan, Po-Chun Hsu, Guangyuan Zheng, Hongbin Yao, Zheng Liang, Xiaoming Sun, and Yi Cui., Nature Communications 5, 4345 (2014).[3] Graeme Gardner, Jafer Al-Sharab, Nemanja Danilovic, Yong Bok Go, Katherine Ayers, Martha Greenblatt, and G. Charles Dismukes., Energy & Environmental Science 9, 184 (2016). Figure 1

Collaborative Electronic Structure Modifier for Iron Single-Atom Electrocatalyst in High-Energy, Long-Cycle Lithium-Sulfur Batteries

In high-energy and long-cycle lithium-sulfur (Li-S) pouch cells, the cathodes often face limitations in their capacities and stability when subjected to practical electrolyte/sulfur (E/S), electrolyte/capacity (E/C), and negative/positive (N/P) ratios. In this study, an advanced cathode incorporating highly active Fe single-atom catalysts (SACs) is presented, enabling the formation of multi-stacked Li-S pouch cells with a total capacity reaching approximately 320.2 Wh/kg at the 1 Ah level. These cells exhibit low E/S (3.0), E/C (2.8), and N/P (2.3) ratios, along with high sulfur loadings of 8.4 mg/cm². The enhanced activity of the Fe SACs is achieved by manipulating their local environments using electron-exchangeable binding (EEB) sites. Introducing EEB sites comprising two different types of sulfur species, namely thiophene-like-S (–S) and oxidized-S (–SO₂), adjacent to Fe SACs enhances the kinetics of the Li₂S redox reaction by providing additional binding sites and adjusting the Fe d-orbital levels via electron exchange with Fe. While –S donates electrons to the Fe SACs, –SO₂ withdraws electrons from them. Consequently, the Fe d-orbital energy level can be regulated by varying the –SO₂/–S ratios of the EEB site, thus controlling their electron-donating/withdrawing characteristics. This desirable electrocatalytic behavior is maximized through the close contact of the Fe SACs with the sulfur species, all of which are confined within porous carbon structures.

(Invited) Insights from Cyclic Voltammetry into Active Sites on Carbon Electrodes and Their Importance in Vanadium Flow Batteries and Other Electrochemical Applications

Flow battery technology is uniquely positioned to fill the niche of long duration energy storage that will be needed to enhance grid reliability and power quality. Vanadium Flow Batteries (VFBs) and other flow battery technologies use carbon as their electrodes. The behaviour of carbon as an electrode is complex and there is considerable variation in the literature regarding the kinetics of flow battery reactions at carbon electrodes.The electrochemical response of a carbon electrode towards redox reactions is known to be improved after electrochemical treatments. For the past decade we have investigated the effect of electrochemical treatment on the electrode activity of carbon towards vanadium redox reactions. We have reported that cathodic treatment in acidic solution enhances the kinetics of the positive (VIV-VV) electrode in VFBs but inhibits the kinetics of the negative (VII-VIII) electrode, while anodic treatment inhibits the kinetics of the positive electrode but enhances the kinetics of the negative electrode1-3. We also showed that the activity of carbon-based material is strongly dependent on the surface history, and in particular on the most positive and the most negative potential used to treat an electrode4.In this presentation, we report some interesting results from our investigations of carbon electrode pretreatment in H2SO4. The cyclic voltammetry behavior which we observe shows a remarkable correlation with kinetics measurements in vanadium-containing electrolytes. We believe that our results provide a novel method of investigating the behavior of active sites on carbon electrodes. This is particularly important in the context of flow battery electrodes but may also, in a much broader context, provide a route to understanding the electrocatalytic behavior of carbon electrodes in many other applications.References. A. Bourke, M. A. Miller, R. P. Lynch, X. Gao, J. Landon, J. S. Wainright, R. F. Savinell and D. N. Buckley, J. Electrochem. Soc. 163, A5097 (2016). A. Bourke, M. A. Miller, R. P. Lynch, J. S. Wainright, R. F. Savinell and D. N. Buckley, J. Electrochem. Soc., 162, A1547 (2015). M. A. Miller, A. Bourke, N. Quill, J. S. Wainright, R. P. Lynch, D. N. Buckley and R. F. Savinell, J. Electrochem. Soc., 163, A2095 (2016). M. Al Hajji Safi, A. Bourke, D. N. Buckley, R. P. Lynch, ECS Trans., 109, 67-84 (2022).

Electrocatalytic Performance and Kinetic Behavior of Anion‐Intercalated Borate‐Based NiFe LDH in Alkaline OER

AbstractThe synthesis of hydrogen via water electrolysis is an important step towards resolving the energy crisis and impeding global warming, as hydrogen can be used as a green energy carrier. The oxygen evolution as one half‐cell reaction (OER) is currently limiting efficient water splitting due to kinetic inhibition as well as a complex mechanism, causing a large overpotential. Nickel‐iron layered double hydroxides (LDH) were found to be suitable OER catalysts, as they are cost effective, stable and highly active. This work focuses on the intercalation of different organic and inorganic borates into the LDH interlayers to study their influence on OER. Besides activity and stability measurements, three borate candidates were chosen for a kinetic study, including steady‐state Tafel analysis and reaction order plots. It was found that the Bockris pathway with the second step as rate‐determining step was predominant for all three catalysts. Of all candidates, the intercalation of borate resulted in the highest performance, which was associated with a high reducibility affecting the active metal sites.

Nitrogen-Doped Graphene-Supported Tungsten Oxynitride Nanoparticles as an Efficient Bidirectional Polysulfide Convertor for Advanced Lithium-Sulfur Batteries.

Catalytic materials are considered pivotal in addressing the sluggish kinetics and shuttle effect in lithium-sulfur batteries (LSBs). However, effectively harnessing the utilization rate of active sites within catalytic materials remains a pivotal challenge. In this study, a novel conductive nitrogen-doped graphene-loaded tungsten oxynitride nanoparticle (WNO/NG) with abundant active sites is prepared through a polymer-assisted templating method for serving as a sulfur host. Electrochemical analysis coupled with in situ XRD confirm the dual-directional electrocatalytic behavior of WNO/NG for accelerating the conversion of lithium polysulfide (LiPSs). Theoretical calculations demonstrate that the intrinsic mechanism underlying the performance enhancement is attributed to the high inherent conductivity of WNO/NG and the efficient interface charge transfer with LiPSs. The assembled 500 mAh pouch cell delivers a 97% capacity retention after 25 cycles. This strategy provides valuable insights for designing catalytic materials with abundant activity sites and sheds light on the mechanisms of catalytic enhancement in Li-S chemistry.

Potential-Driven Coordinated Oxygen Migration in an Electrocatalyst for Sustainable H2O2 Synthesis.

Local coordination environment (LCE) manipulation has emerged as a significant approach for modulating the electrocatalytic behavior of low-dimensional nanomaterials. However, challenges persist in accurately identifying active sites and understanding dynamic changes during operation. Here, we underscore the influence of LCE on the electrochemical production of H2O2, utilizing the Pd cluster as a model catalyst. Density functional theory (DFT) calculations illustrate the role of first- and second-coordinated sulfur and oxygen in modulating the binding strength of HOO*. Guided by DFT screening, the as-prepared Pd cluster (Pdx/HMCS) catalyst presents exceptional catalytic performance with a high mass activity of 4.06 A mg-1 at 0.45 V and selectivity above 94%. The Pdx/HMCS catalyst also delivers promising potential for industrial practices with a production rate of 16.3 mol gcat-1 h-1 in flow cell evaluation. Elaborated in situ characterizations confirm that under operation, oxygen migrates from the second coordination sphere (CS) to the first CS to achieve oxygen coverage on the catalyst surface. Such an oxygen migration phenomenon and the optimized first and second coordination environment give rise to the outstanding performance.

Ultrasonic synthesis of MOF-based hybrid composite for electrochemical detection of furazolidone antibiotic in food and biological samples

This study reveals the development of a new combination of Bi-MOF/ functionalized carbon nanofiber (f-CNF) composite modified electrode for the electrochemical sensing of Furazolidone (FUZ) antibiotics. FUZ is used to prevent bacterial infections in animals, and an overdose of FUZ leads to several health issues. Bi-MOF/f-CNF provide excellent surface area, high conductivity, and electrocatalytic activity for the effective detection of FUZ. Various characterization techniques were used to analyze the structural, morphological and compositional properties of Bi-MOF/f-CNF. The fabricated composite coated onto glassy carbon electrode (GCE) and rotating disk glassy carbon electrode (RDGCE) to study its electrocatalytic behavior using different voltammetry techniques. Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) analysis of the electrode material confirmed its high electroactive surface area, low charge transfer resistance, and excellent charge transfer ability. The electrochemical quantification of FUZ was performed using differential pulse voltammetry (DPV) and amperometric (i-t) techniques. The linear range, limit of detection (LOD) and sensitivity are 0.199 to 238 μM, 20.8 nM and 43.99 μA μM−1 cm−2, respectively, as determined by the DPV technique. Additionally, the LOD, linear range and sensitivity were obtained as 3.64 nM, 0.002 to 700 μM and 0.827 μA μM−1 cm−2, respectively using i-t quantification technique. The invented electrode material exhibits better stability in the presence of other interference molecules and it shows good repeatability and reproducibility for the detection of FUZ. Due to the excellent analytical properties, the Bi-MOF/f-CNF modified electrode could be the potential contender for the electrochemical detection of FUZ in the real samples.

Polyaniline prepared by Fe3O4 catalysed eco-friendly synthesis as electrocatalyst for efficient water electrolysis

Preparing cost-effective and highly active catalysts for electrocatalytic hydrogen evolution reaction is crucial for developing hydrogen-based technologies. Hence, four conductive polyanilines, prepared by the environmentally-friendly approach using Fe3O4 nanoparticles/H2O2 as the catalyst/main oxidant system (PANI/Fe3O4), were investi¬gated for the first time as electrocatalysts for hydrogen evolution reaction (HER) in acidic media (0.1 M H2SO4) by using voltammetry and chronoamperometry. PANI/Fe3O4 electrodes exhibited Tafel slope values in the -171 to -246 mV dec-1 range depending on the synthesis conditions ‒ Fe3O4/aniline mass ratio and polymerization time. The sample PANI/Fe3O4-II(3) prepared with shorter reaction time and higher Fe3O4/aniline mass ratio showed the best electrocatalytic behaviour reflected in the lowest onset potential (-0.286 V), the lowest overpotential to reach a current density of -10 mA cm-2, the highest current density, the lowest HER activation energy (10 kJ mol-1), and the lowest charge-transfer resistance (5.3 Ω) under HER conditions. Materials were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray photo¬electron spectroscopy and electrochemical impedance spectroscopy, and differences in their electrocatalytic HER performance were explained by differences in their content of Fe3O4, surface and electrical properties. Moreover, the possibility of using PANI/Fe3O4-II(3) as HER electrocatalyst in a wider range of pH (i.e. in alkaline media as well) and as a bifunc¬tional electrocatalyst, i.e., for oxygen evolution reaction beside HER, was also examined.

Developing Practical Catalysts for High‐Current‐Density Water Electrolysis

AbstractHigh‐current‐density water electrolysis is considered a promising technology for industrial‐scale green hydrogen production, which is of significant value to energy decarbonization and numerous sustainable industrial applications. To date, substantial research advancements are achieved in catalyst design for laboratory‐based water electrolysis. While the designed catalysts demonstrate remarkable performance at laboratory‐based low current densities, they suffer from marked deteriorations in both activity and long‐term stability under industrial‐level high‐current‐density operations. To provide a timely assessment that helps bridge the gap between laboratory‐scale fundamental research and industrial‐scale practical water electrolysis technology, here the current advancements in various commercial water electrolyzers are first systematically analyzed, then the key parameters including work temperature, current density, lifetime of stacks, cell efficiency, and capital cost of stacks are critically evaluated. In addition, the impact of high current density on the electrocatalytic behavior of catalysts, including intrinsic activity, long‐term stability, and mass transfer, is discussed to advance the catalyst design. Therefore, by covering a range of critical issues from fundamental material design principles to industrial‐scale performance parameters, here the future research directions in the development of highly efficient and low‐cost catalysts are presented and a procedure for screening laboratory‐designed catalysts for industrial‐scale water electrolysis is outlined.

Enhanced detection of glyphosate with a Co-MOF integrated opto-electrochemical sensor

Abstract This study presents a new method for detecting the organophosphorus pesticide glyphosate using advanced scanning electrodes (SPE) and enhanced fluorescence. Metal-organic frameworks from cobalt ions were synthesized using a solvothermal method. It is characterized using Raman spectroscopy, FT-IR, and X-ray diffraction techniques. The electrocatalytic behavior of the materials was studied using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Differential pulse voltammetry (DPV) examined the positive response of plants to glyphosate over a concentration range of 0.55–5.95 mM with a detection limit of 0.334 mM. The fluorescence enhancement ranges from 0.07 mM to 0.67 mM, and the detection limit is 0.0998 mM. Additionally, the selectivity of the proposed opto-electrochemical sensor was evaluated. This selection demonstrates the sensor's ability to detect glyphosate in complex wastewater matrices. This has important implications for environmental monitoring. By addressing glyphosate contamination, the sensor could significantly advance ecological remediation and monitoring strategies. The selectivity, sensitivity, and ability to operate under harsh conditions represent a significant advance in the development of efficient and reliable glyphosate technology for wastewater treatment and environmental protection. In real-sample matrices, the suggested sensor showed a good recovery of the pesticide that had been spiked.

Ferrocenyl Dithiophosphonate Ag(I) Complexes: Synthesis, Structures, Luminescence, and Electrocatalytic Water Splitting Tuned by Nuclearity and Ligands.

The heterometallic [Ag(I)/Fe(II)] molecular electrocatalysts for hydrogen production were introduced here to recognize the mutual role of metallic nuclearity and ligand engineering. A series of ferrocenyl dithiophosphonate stabilized mononuclear [Ag(PPh3)2{S2PFc(OR)}] {where R=Me (1), Et (2), nPr (3), iPr (4), iAmyl (5); Fc=Fe (ɳ5-C5H4) (ɳ5-C5H5)} and dinuclear [Ag(PPh3){S2PFc(OR}]2 {where R=Et (2 a), and nPr (3 a)} complexes were synthesized and characterized by SCXRD, NMR (31P and 1H), ESI-MS, UV-Vis, and FT-IR spectroscopy. The comparative electrocatalytic HER behavior of 1-5 and 2 a-3 a showed effective current density of 1 mA/cm2 with overpotentials ranging from 772 to 991 mV, demonstrating the influence of extended and branched carbon chains in dithiophosphonates and metallic (mono-/di-) nuclearity, which correlates with documented tetra-nuclear [Ag4(S2PFc(OnPr)4], 6. DFT study suggests the coordinated (μ1-S) site of ligands is the reactivity center and the adsorption energy of intermediate [H*-SM] varies with the engineering of ligand and nuclearity. A catalytic mechanism using mononuclear (1) and di-nuclear (2 a) was proposed with the assistance of DFT. Each complex, being the first example of Ag(I) dithiophosphonates, exhibits intense photoluminescence with high quantum yields ranging from 33 % to 67 %. These results link the lower nuclearity structures to their physical and catalytic properties.

Unlocking the Electrocatalytic Behavior of Cu2MnS2 Nanoflake-Anchored rGO for the Oxygen Evolution Reaction in an Alkaline Medium.

A catalyst of the oxygen evolution reaction (OER) that is viable, affordable, and active for effective water-splitting applications is critical. A variety of electrocatalysts have been discovered to replace noble metal-based catalysts. Of these, transition metal-based sulfides are essential for incorporating carbonaceous materials to improve electrical conductivity, resulting in better electrocatalytic performance. Our study illustrates the synthesis of Cu2MnS2 (CMS) nanoflakes and their different rGO composites (10 to 40 wt %) via a hydrothermal technique for an effective water oxidation reaction. The X-ray diffraction pattern reveals that the prepared Cu2MnS2 nanoflakes exhibit a cubic crystal structure. The high-resolution scanning electron microscopy and the high resolution transmission electron microscopy images corroborate the formation of the nanoflake-like morphology of Cu2MnS2 with the strong interaction of rGO. The selected area electron diffraction analysis pattern reveals a polycrystalline nature. The Fourier transform infrared spectrum shows the existence of a metal sulfur vibrational band at 590 cm-1, and Raman analysis infers the presence of rGO. The X-ray photoelectron spectroscopy spectra reveal the oxidation states of the elements present in the samples. Using Brunauer-Emmett-Teller analysis, the surface area of CMS-20 is found to be 117.04 m2/g. The measured OER overpotentials using linear sweep volammetry and the values are 380, 370, 340, 376, and 400 mV at 10 mA/cm2 for CMS, CMS-10, CMS-20, CMS-30, and CMS-40, respectively, and the corresponding Tafel slope values are 179, 158, 149, 206, and 240 mV/decade, respectively. The electrochemical active surface area is estimated using cyclic voltammetry for all of the catalysts, where CMS-20 showed a larger surface area. Also, the same catalyst exhibits good stability for ∼24 h at a constant potential, which is confirmed via chronoamperometry. Thus, combining transition metal-based sulfides with carbonaceous materials indicates improved catalytic behavior for the preparation of high-performance OER electrocatalysts. Overall, the prepared CMS-20 performed as an efficient OER electrocatalyst and can be utilized for practical applications in energy conversion.

The influence of amino anchoring position on SnO2/biochar for electroreduction of CO2 to HCOOH

Biochar derived from biomass resources as a carrier to load SnO2 for electroreduction of CO2 not only can benefit carbon emissions, but it also can achieve waste utilization. However, the weak CO2 mass transfer and conductivity ability of SnO2/biochar limits its applications to such eCO2RR processes. This study focused on modifying SnO2/biochar with amino groups and investigated the effects of positioning of amino groups on the catalyst’s physicochemical properties and electrocatalytic behaviors. Elemental analysis revealed that anchoring amino groups on biochar (SnO2/C-NHx) is advantageous for increasing amounts of amino groups attached, thereby enhancing biochar adsorption energy and subsequently increasing the loading of Sn. The CO2 adsorption curve indicated that amino groups anchored on biochar facilitate CO2 adsorption due to high specific surface area of biochar. X-ray photoelectron spectroscopy showed that amino groups anchored on SnO2 (NHx-SnO2/C) resulted in highly electron-rich centers on Sn, which promoted electron transfer between the catalyst and CO2. Electrochemical tests demonstrated the improved performance of amino-modified SnO2/biochar. SnO2/C-NHx exhibited enhanced Faraday efficiency, whereas NHx-SnO2/C showed higher current density. The disparity in electrochemical performance can be mainly attributed to the different selectivity towards rate-controlling steps of electron transfer and mass transfer induced by the various positions of amino groups anchoring.

Substrate and potential-driven surface morphology of bifunctional Ni-Fe electrode for efficient alkaline water electrolysis

Nickel-iron (Ni-Fe) alloy electrodes are synthesized using chronoamperometry. The influence of substrate type (copper, stainless steel, and nickel) and deposition potential on the structural, morphological, and electrocatalytic characteristics are systematically investigated. X-ray diffraction (XRD) analysis revealed the formation of a face-centered cubic (FCC) Ni-Fe alloy. Electrodeposition at higher potential (−1.45 V) forms well-defined nanoflakes, whereas electrodeposition at lower potential (−1.00 V) results aggregated Ni-Fe particles. The Ni-Fe alloy electrodes having well-defined nanoflakes demonstrated superior electrocatalytic performance, exhibiting a overpotential of −168 mV vs. RHE for the hydrogen evolution reaction (HER) and 236 mV vs. RHE for the oxygen evolution reaction (OER), at current density of 10 mA/cm2. The enhanced electrocatalytic activity of the nanoflakes based Ni-Fe alloy is attributed due to their larger catalytic surface area, porous morphology and higher Fe concentration. The Ni-Fe alloy electrodes displayed bifunctional electrocatalytic behavior, making them highly suitable for both HER and OER processes.