High Electrocatalytic Activity Research Articles

Layer interfacing strategy to derive free standing CoFe@PANI bifunctional electrocatalyst towards oxygen evolution reaction and methanol oxidation reaction

Developing inexpensive, highly electrochemically active, and stable catalysts towards electrochemical studies remains challenge for researchers. In this regard, binder-free CoFe@PANI composite electrocatalyst is deposited on nickel foam (NF) substrate via successive electrodeposition of polyaniline (PANI) and CoFe-LDH at Room temperature (RT). As deposited binder-free CoFe@PANI electrocatalyst displays high electrocatalytic activity towards oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) in alkaline media. In CoFe@PANI structure, interfacing of high-electron conducting PANI establishes strong interconnection with CoFe-LDH by tuning electronic structures, which accelerates the electrochemical performance towards OER and MOR. For OER, CoFe@PANI requires low overpotential (η10) of 237 mV to reach current density (Id) of 10 mA cm−2 and displays low Tafel slope value of 46 mV dec−1 in 1 M KOH solution. Also, it displayed specific Id of 120 mA cm−2, when it was tested for MOR in 1 M KOH with 0.5 M methanol solution. The superior electrocatalytic activity of CoFe@PANI is mainly ascribed to high electrochemical active surface area (ECSA), abundant active sites and fast electron transfer between electrocatalyst and electrode surface. Of note, the current work may open new era for design and development of non-precious highly active and stable hybrid electrocatalysts at RT for various applications.

In-situ fabrication of bimetallic FeCo2O4-FeCo2S4 heterostructure for high-efficient alkaline freshwater/seawater electrolysis

Rational construction of bifunctional electrocatalysts with long-term stability and high electrocatalytic activity is of great importance, but it is challenging to obtain highly efficient non-precious metal-based catalysts for overall seawater electrolysis. Herein, a nickel foam (NF) self-supporting CoFe-layered double hydroxide (CoFe-LDH/NF) was directly converted into FeCo2O4-FeCo2S4 heterostructure via hydrothermal method in 50 mM Na2S solution, instead of FeCo2O4@FeCo2S4 core-shell structure. The FeCo2O4-FeCo2S4 heterojunction shows nanosheets structure with rough surface (the thickness of ∼ 198.9 nm), which provides rich oxide/sulfide interfaces, high electrochemical active area, a large number of active sites, as well as fast charge and mass transfer. In 1.0 M KOH solution, 1.0 M KOH + 0.5 M NaCl, and alkaline natural seawater, the FeCo2O4-FeCo2S4 heterojunction exhibits eminently electrocatalytic performance, with overpotentials of η-100 = 225 mV, η-100 = 233 mV, and η-100 = 238 mV for OER, as well as η-100 = 271 mV, η-100 = 273 mV, and η-100 = 277 mV for HER, respectively. Furthermore, self-supporting FeCo2O4-FeCo2S4 electrode (FeCo2O4-FeCo2S4/NF) as the cathode and anode of an electrolyzer exhibits a lower cell voltage of E-100 = 1.75 V in alkaline seawater than those of FeCo2S4/NF (1.77 V), CoFe-LDH/NF (1.87 V), and FeCo2O4/NF (1.91 V). Specifically, FeCo2O4-FeCo2S4 electrolyzer can stably produce hydrogen for over 48 h in alkaline freshwater/seawater electrolyte. These outstanding electrocatalytic performances and corrosion resistance to salty-water can be attributed to the surface reconstruction behavior of the FeCo2O4-FeCo2S4/NF catalyst during OER, which leads to the in-situ formation of metal oxyhydroxides. In particular, the FeCo2O4-FeCo2S4 heterojunction is also very competitive among most state-of-the-art non-noble metal-based catalysts, whether in KOH or alkaline salty-water electrolytes.

Highly defective graphene quantum dots-doped 1T/2H-MoS2 as an efficient composite catalyst for the hydrogen evolution reaction

We present a new composite catalyst system of highly defective graphene quantum dots (HDGQDs)-doped 1T/2H-MoS2 for efficient hydrogen evolution reactions (HER). The high electrocatalytic activity, represented by an overpotential of 136.9 mV and a Tafel slope of 57.1 mV/decade, is due to improved conductivity, a larger number of active sites in 1T-MoS2 compared to that in 2H-MoS2, and additional defects introduced by HDGQDs. High-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were used to characterize both the 1T/2H-MoS2 and GQDs components while Fourier-transform infrared spectroscopy (FTIR) was employed to identify the functional groups on the edge and defect sites in the HDGQDs. The morphology of the composite catalyst was also examined by field emission scanning electron microscopy (FESEM). All experimental data demonstrated that each component contributes unique advantages that synergistically lead to the significantly improved electrocatalytic activity for HER in the composite catalyst system.

A review of typical transition metal phosphides electrocatalysts for hydrogen evolution reaction

Hydrogen energy is a clean, carbon-free and potential future energy source. Hydrogen generation by electrochemical water splitting becomes a promising approach, which is highly dependent on the electroactivity of hydrogen evolution reaction (HER) electrocatalysts. The transition metal phosphides (TMPs) become promising electrocatalysts due to low overpotential, good electrochemical stability and high electrocatalytic activity. This review mainly summarizes HER mechanisms, preparation methods, electrocatalytic assessment and microstructure regulation of TMPs. The electrochemical properties of five typical TMPs (NixPy, CoxPy, MoxPy, WxPy and FexPy) under different phosphating degrees are intensively compared. Since the electrocatalytic performance of current TMPs is insufficient for industrial applications, new design and preparation methods for nanostructure-controlled TMPs electrocatalysts are proposed. In particular, the development of element-doped, self-supporting nanomaterials is the future development direction of TMPs electrocatalysts that can be applied in the whole pH range.

Fe-Ni alloy modified Zr-based MOF derivatives as bioelectrocatalyst for regulating multipath EET efficiency and biofilm electrogenic activity

As a green conversion device, the electricity performance of microbial fuel cell (MFC) was mainly affected by the extracellular electron transfer (EET) process of the biofilm. This paper presented the fabrication and characterization of carbonized derivatives composed with alloy nanoparticles (NPs) derived from Zr-based metal organic frameworks, which exhibited biocompatibility and high electrocatalytic activity. As the results of bioanodes, the charge transfer resistance decreased from 5.60 Ω (Zr-C) to 0.61 Ω (Fe/Ni-Zr-C), and the exchange current density increased from 0.56 mA/cm2 (Zr-C) to 1.40 mA/cm2 (Fe/Ni-Zr-C). Electrochemical tests and density functional theory (DFT) confirmed that Fe-Ni alloy NPs promoted the rapid transfer of electrons within the electrode and improved the EET efficiency mediated with the flavin compounds. High throughput sequencing and PICRUSt verified the specific screening function of Fe-Ni alloy for electrogenic bacteria (mainly Geoalkalibacter) and the promoting effect on the expression of flavin-related proteins in biofilm. The maximum power density of Fe/Ni-Zr-C MFC (5.09 W/m2) was higher than that of Ni-Zr-C (4.19 W/m2), Fe-Zr-C (3.58 W/m2) and Zr-C (3.09 W/m2) MFCs. Fe/Ni-Zr-C material can act as an economical and high-performance bioelectrocatalyst to improve the power generation capability of MFC by improving EET rate and energy conversion efficiency of biofilm.

Simultaneous electrochemical determination of benzenediol compounds in environmental samples using nano architectures of hydrogen ammonium zinc molybdate layered double hydroxides integrated with carbon black modified electrode

Phenolic compounds, such as benzenediol (BD), are toxic and exhibit poor biodegradability, posing a threat to human health and the environment, even at low concentrations. Therefore, the simultaneous detection of BD at low detection limits and a wide detection range is of significant interest for monitoring water quality and environmental remediation efforts. In this study, we developed a novel electrochemical sensor for BD based on a nanocomposite (NC) of hydrogen ammonium zinc molybdate layered double hydroxide (AZnMo-LDHs) and carbon black (CB) as a modification for the electrode. Various characterization methods were employed to verify the morphological, structural, and physical-chemical properties of AZnMo-LDHs/CB NC. The NC-modified electrode exhibited low electrical resistance, high electrocatalytic activity, and fast electron transport, thanks to the synergistic effects between AZnMo-LDHs and CB. Additionally, the NC-modified electrode demonstrated excellent electrochemical performance in selectively and simultaneously detecting hydroquinone (HQ), catechol (CC), and resorcinol (RC). Differential pulse voltammetric studies confirmed that AZnMo-LDHs/CB NC enabled the detection of HQ, CC, and RC within linear response ranges of 0.05–971 μM, 0.1–1036 μM, and 0.5–1408.5 μM, respectively, with detection limits of 0.0054 μM, 0.0018 μM, and 0.075 μM. To validate the sensor's practical application, we tested it with multiple environmental samples, including water and soil, and obtained excellent recovery rates for HQ, CC, and RC.

Novel air-electrode materials for low-cost inert-supported solid oxide cells: investigation of materials compatibility during co-sintering

AbstractFor the investigation of the reactivity of alternative solid oxide cell air electrode materials with forsterite (Mg2SiO4), a magnesium silicate doped with Zn and Ca, five different phase materials were chosen: two Ruddlesden–Popper phase materials: La4Ni3O10 (L4N3) and La3Ni2O7 (L3N2) and three titanium-based perovskite materials: SrTiO3 (STO), SrTi0.75Fe0.25O3 (STF25) and CaTi0.9Fe0.1O3 (CTF). Forsterite was chosen as a support material for the fuel cell, as it is abundant and therefore relatively inexpensive. For the investigation of their reactivity, different types of samples were prepared: mixed pellets, double-layered pellets and screen-printed electrode inks on forsterite green substrates, which were subsequently co-sintered at T = 1300 °C. These samples and their cross sections were then studied using XRD, SEM, EDS and TEM lamella point analysis. Consequently, the impedance spectra were acquired to determine their electro-catalytic performance. The two Ruddlesden–Popper phase materials L4N3 and L3N2 are of high interest due to their thermodynamic stability and high electro-catalytic activity, resulting in a very low polarization resistance. However, this polarization resistance is increased when mixing with forsterite material. In case of the three titanium-based perovskites, the electro-catalytic activity is of less interest due to high polarization resistances.

Synthesis of a Ni(OH)2@Cu2Se hetero-nanocage by ion exchange for advanced glucose sensing in serum and beverages.

Cu2Se nanosheets were coated on the surface of Ni(OH)2 nanocages (NCs) by ion exchange driven by selenium incorporation. The resulting Ni(OH)2@Cu2Se hollow heterostructures (Ni(OH)2@Cu2Se HHSs) showed high electrical conductivity and electrocatalytic activities derived from the synergistic effects of Ni/Cu phases. These structures enhanced glucose adsorption abilities, confirmed by density function theory (DFT) calculations, and the robustness of the integrated nano-electrocatalyst. Remarkably, Ni(OH)2@Cu2Se HHSs modified electrodes excited excellent glucose sensing behavior with a wide linear range (0.001-7.5mM), a sensitivity up to 2420.4ΜamM-1 cm2, a low limit of detection (LOD, 0.15μM), and fast response (less 2s). Furthermore, Ni(OH)2@Cu2Se HHSs competently analyzed glucose in serum and beverages with good recoveries ranging from 94.4 to 103.6%. Integrating copper selenide and Ni-based materials as 3D hollow heterostructures expands the selection of electrocatalysts for sensitive glucose detection in food and biological samples.

Enhanced Hydrogen Evolution Performance of Ni−Mo-Based Electrocatalysts in Seawater by Controlling Surface Wettability

Environmental pollution and global warming have become enormous problems all over the world. At the United Nations Climate Change Conference, carbon neutrality was proposed as a way to solve this problem through the Paris Agreement in 2015. To achieve zero net carbon dioxide emissions, research on how to obtain energy from renewable energy resources has been intensively conducted. Among various candidates of renewable chemical fuels, green H2, produced by water electrolysis is considered as one of the promising, next generation chemical fuels.Almost 97% of earth’s water resources exist as seawater. Moreover, seawater has an advantage that it can be used as an electrolyte owing to the various ions, existing naturally. Therefore, one of the ultimate goals in green H2 generation is to directly utilize seawater as the electrolyte source.Although Pt-group materials (PGMs) are well known catalysts in hydrogen evolution reaction (HER) but one of the main challenges for wide commercialization with PGMs is its high cost and scarcity. In order to overcome this issue, research on HER catalysts using non-PGM (NPGM) has been intensively performed. Among various NPGM elements, Ni−Mo has great potential for electrocatalysts in HER owing to its cost effectiveness as well as their high electrocatalytic activities in wide pH range of electrolytes. It is well known that not only the electrocatalytic activity in HER, mainly originating from chemical compositions at the surface, but also the physical surface properties, especially the surface wettability, play an important role to regulate the electrocatalytic performance. The evolved bubbles by the HER form the solid−gas−liquid interfaces, which results in the turn-off of the active sites toward electrochemical reactions until the gas bubbles remove from the electrocatalytic surface. Previous studies reveal that this dynamic, evolutionary behavior of surface active sites by the bubble growth/departure significantly influence the electrocatalytic performance.Herein, we demonstrate the Ni−Mo-based material as the electrocatalyst toward HER in simulated seawater, which is 0.5 M phosphate buffer with 0.6 M NaCl. The electrocatalytic layers are deposited by simple electrodeposition with the aminated graphene oxide (aGO) to form composites (aGO/NiMo). The addition of aGO in Ni−Mo does not influence the electrocatalytic activity in HER, exhibiting nearly the same cyclic voltammograms with pure NiMo. Interestingly, the long-term performance of aGO/NiMo, however, is observed when compared to the pure NiMo. The enhanced durability by chronopotentiometric measurements in the aGO/NiMo is ascribed to the improved surface wettability, originating from added aGO. The images taken by high-speed camera clearly show that the H2 bubbles with smaller sizes at the surface of aGO/NiMo but much larger density than the ones at pure NiMo are observed. These phenomena denotes that the regeneration rate of active sites by bubbles departure from the surface is much higher in the aGO/NiMo than NiMo without aGO, indicating that the aGO is beneficial for improving the surface wettability. The longer residence of H2 bubbles at the pure NiMo increases the actual overpotential applied in the single active site under constant current density, leading to the faster degradation of electrocatalytic activity in HER. The physical properties of surface between aGO/NiMo and NiMo for surface wettability is also supported by surface roughness measurements in atomic force microscope and contact angles. Our study contributes to the fundamental design of the physical properties of electrocatalytic surfaces physical properties, thereby simply improving the electrochemical performance in HER.

Cu-Content La1−XSrxNi1−YCuyO3−Δ Perovskites As Cobalt-Free Cathode Materials for High-Performance It-SOFCs

Solid Oxide Fuel Cells (SOFCs) are one of the most attractive energy conversion and storage devices, which can be applied for decentralized energy applications. However, the high operating temperature making SOFCs still unmarketable, which indicates that lowering the working temperature of SOFCs while still maintaining a high-power output is very crucial. For Intermediate-Temperature Solid Oxide Fuel Cells (IT-SOFCs), new cathode materials with high electrocatalytic activity and stability are necessary to provide a stable and high performance of cells. Perovskite-structured oxide (ABO3−δ) is one group of the most interesting material candidates for IT-SOFCs, presenting great potential in chemical composition modifications, yielding the design and gain of desired physicochemical and electrochemical properties [1]. The simple perovskite LaCuO3 is one of the well-studied Cu-content oxides with a high conductivity (106 S·cm−1), but it can be hardly obtained and suffers with stability issues in air [1, 2]. To stabilize the perovskite structure and to improve electrochemical properties of Cu-content oxides A-site and B-site modification strategy can be applied. It has been noted that Cu- and Ni-containing LaNi0.5Cu0.5O3−δ simple perovskite possesses low cathodic polarization of 0.056 Ω·cm2 at 800 °C, and a high power output of 870 mW·cm−2 at 900 °C [1, 3]. The generation of oxygen vacancies by strontium doping contributes to the increase of ionic conductivity component, and the Sr dopant can reduce the oxygen vacancy formation energy and increase the ionic conductivity of La1−xSrxMO3−δ (M = Fe, Mn) perovskites [1,4]. Therefore, in this work, Cu-content La1−xSrxNi1−yCuyO3−δ oxides with strontium doping at the A-site were evaluated as very promising Co-free cathode material candidates for IT-SOFCs.In this work, all La1−xSrxNi1−yCuyO3−δ compounds have been successfully obtained using soft chemistry. The room-temperature crystal structure of all oxides was assigned to the R-3c trigonal system. The substitution of La with Sr lowers the phase transition temperature from the R-3c space group to Pm-3m simple perovskite while increases the oxygen non-stoichiometry and the thermal expansion coefficient of studied materials. All investigated materials are chemically compatible with GDC-10, while unstable in contact with LSGM and 8YSZ. The manufactured anode-supported IT-SOFC with the La0.95Sr0.05Ni0.5Cu0.5O3−δ cathode presents an excellent power density of 445 mW·cm−2 at 650 °C in humidified H2. The results confirmed that La1−xSrxNi1−yCuyO3−δ perovskites can be potentially qualified as promising cathode candidates for IT-SOFCs, yielding promising electrochemical performance in the intermediate-temperature range [1].

Electrochemical Activity and Stability of Pure Gadolinium Doped Ceria as Fuel Electrode in Solid Oxide Electrolysis Cells

The state-of-the-art fuel electrode materials for solid oxide electrolysis cells (SOECs) are Ni-cermets due to their high electro-catalytic activity, high electrical conductivity and the low price. However, one major concern that must be solved for a widespread commercialisation is their poor degradation behaviour during electrolysis operation caused by for example Ni migration, depletion and agglomeration in the fuel electrode. One strategy to improve the durability of SOECs is the usage of alternative fuel electrode materials. For instance, completely Ni-free fuel electrodes may solve the problems of morphological degradation during operation and further could enhance redox cycling stability. Within possible candidates, gadolinium doped ceria (GDC) is an interesting material due to good stability towards carbon deposition and the possibility to host electro catalysis in electrolysis reactions [1, 2]. Furthermore, GDC (Ce0.8Gd0.2O2-δ) shows electronic conducting (700 °C, 0.028 S·cm-1) and ionic conducting (700 °C, 0.47 S·cm-1) properties at low partial pressures of oxygen and high temperatures [3]. Hence, in this work we have prepared electrolyte supported single cells with GDC (Ce0.8Gd0.2O2- δ) as single phase fuel electrode for their use as SOEC. The single cells (GDC//8YSZ//GDC//LSCF) were characterized by electrochemical impedance spectroscopy (EIS) and current-voltage characteristics in steam electrolysis, co-electrolysis and CO2 electrolysis conditions exhibiting 70 % of the performance compared to similar produced Ni-GDC fuel electrode single cells at 900 °C [4]. Furthermore, the results include process analysis by EIS, long term stability experiments for steam electrolysis and CO2 electrolysis conditions of at least 1000 hours and post characterization of the degraded cells by EIS, SEM and EDX analysis.[1] Nakmura et al. Journal of the Electrochemical Society 155 (2008) B563.[2] Chueh et al. Nature Materials 11 (2012) 155-161.[3] Maricle et al. Solid State Ionics 52 (1992) 173-182.[4] Unachukwu et al. Journal of Power Sources 556 (2023) 232436. Figure 1

Modification of Misfit-Layered Cathode Materials for Improving Electrocatalyic Activity in Reversible Protonic Ceramic Cells

The demand for sustainable regeneration energies such as solar and wind has been continuously increasing by the rise of environmental issues. However, several major technical issues such as intermittent electricity production and high system construction cost are major obstacles to large-scale commercialization for regeneration energies [1]. Reversible protonic ceramic cells (RPCCs) can be an alternative choice because of their high efficiency, long-term durability at intermediate temperatures, and bifunctionality for producing both hydrogen and electricity in an electrochemical device [2]. Until now, perovskite-structured cathode (air/steam electrode) materials have been in spotlight due to their fast oxygen reaction kinetics in RPCCs [3]. However, in spite of their high electrocatalytic activity for oxygen electrode reactions (oxygen evolution and reduction), low phase stability in humid atmospheres, thermal expansion mismatch to common proton electrolytes, and relatively low proton conductivity of RPCCs are still major obstacles to enter the era of hydrogen economy [4, 5]. Hence, we demonstrate novel misfit-layered structure Ca3Co4O9+δ (CCO)-based materials to overcome these technical issues with superior catalytic activity for high performance RPCCs. The thermal expansion coefficient value of CCO is 10-12×10−6 K−1, which is relatively similar to that of the BaCeO3-based proton electrolytes, implying that the CCO-based materials are thermo-mechanically stable during cell operations [6]. In addition, the needle-like morphology of the CCO-based materials is quite valuable in the supply of steam (or air) to the catalytic active sites and elimination the water produced by the electrochemical reaction. Furthermore, with the doping of alkali metal ion (Li, Na, and K) into Ca-site, CCO generates extra charge carrier species with the modified Co oxidation state. This triggers the proton uptake and diffusion properties of CCO-based materials with the improved electrical conductivity. As a result, 5 mol% Na-doped CCO-cell shows exceptionally high performance in both protonic ceramic fuel cell and electrolysis cell modes for RPCCs.

2D/2D heterostructure Ni-Fe LDH/black phosphorus nanosheets with AuNP for noxious substance diphenylamine detection in food samples

In this study, gold nanoparticles decorated on nickel–iron layered double hydroxide with black phosphorus nanosheets (AuNP/Ni-Fe LDH/BPNSs) composite were prepared using a stirring method. Analyte tracing is required for developing viable sensors. The AuNP/Ni-Fe LDH/BPNSs composite exhibited a large specific surface area, high conductivity, high electrocatalytic activity, and rapid electron transfer. These properties play a vital role in monitoring diphenylamine (DPA) in food samples. The formation of the AuNP/Ni-Fe LDH/BPNSs composite was confirmed using various structural and morphological characterization techniques. The electroanalytical character of the AuNP/Ni-Fe LDH/BPNSs composite was evaluated using voltammetry. Interestingly, the AuNP/Ni-Fe LDH/BPNSs showed a wide linear range of 0.0125–1003.82 μM and a detection limit of 4.63 nM with a sensitivity of 0.399 µA µM−1 cm−2. The constructed sensor shows considerable selectivity, stability, repeatability, and reproducibility, and the practicability of DPA was monitored in the apples, sweet tomatoes, pears, and grapes with satisfactory recoveries.

Bimetallic CoCu nanoparticles anchored on COF/SWCNT for electrochemical detection of carbendazim

Carbendazim (CBZ) is a widespread fungicide used in crop protection, but the CBZ residues in drinking water, fruits, and vegetables can also cause adverse impacts on public health due to direct exposure. In this paper, a ternary synergistic composite of bimetallic CoCu nanoparticles anchored on covalent organic framework/single-walled carbon nanotube (CoCu/COF/SWCNT) was prepared and further applied as an electrochemical sensing platform for detecting CBZ. The sensor showed a sensitive response performance toward CBZ oxidation, as a result of the enhanced charge transfer ability, large electrochemically active surface area, and high electro-catalytic activity from the rational integration of the ternary components in CoCu/COF/SWCNT. Under the optimal conditions, the proposed sensor exhibited a detection range of 0.001 to 10 μM and a limit detection of 0.65 nM for CBZ detection. In addition, the sensor displayed practical feasibility for the determination of CBZ in water and pear samples with a recovery of 96.1 % to 102.1 %.

Heterostructured Cobalt Silicide Nanocrystals: Synthesis in Molten Salts, Ferromagnetism, and Electrocatalysis.

Nanoscale heterostructures of covalent intermetallics should give birth to a wide range of interface-driven physical and chemical properties. Such a level of design however remains unattainable for most of these compounds, due to the difficulty to reach a crystalline order of covalent bonds at the moderate temperatures required for colloidal chemistry. Herein, we design heterostructured cobalt silicide nanoparticles to trigger magnetic and catalytic properties in silicon-based materials. Our strategy consists in controlling the diffusion of cobalt atoms into silicon nanoparticles, by reacting these particles in molten salts. By adjusting the temperature, we tune the conversion of the initial silicon particles toward homogeneous CoSi nanoparticles and core-shell nanoparticles made of a CoSi shell and a silicon-rich core. The increased interface-to-volume ratio of the CoSi component in the core-shell particles yields distinct properties compared to the bulk and homogeneous nanoparticles. First, the core-shell particles exhibit increased ferromagnetism, despite the bulk diamagnetic properties of cobalt monosilicide. Second, the core-shell nanoparticles act as efficient precatalysts for alkaline water oxidation, where the nanostructure is converted in situ into a layered cobalt silicon oxide/(oxy)hydroxide with high and stable oxygen evolution reaction (OER) electrocatalytic activity. This work demonstrates a route to design heterostructured nanocrystals of covalent intermetallic compounds and shows that these new structures exhibit very rich, yet poorly explored, interface-based physical properties and reactivity.

Nanocomposite of Electrochemically Reduced Graphene Oxide and Poly (p‐aminobenzenesulfonic acid) Incorporated with Ni (II) Ions as an Electrocatalyst for the Oxidation of Methanol

AbstractA new nanocomposite containing Ni(II) ions, electrochemically reduced graphene oxide (ERGO) and poly (p‐aminobenzenesulfonic acid) (Pp‐ABSA) on pencil graphite electrode (PGE) was prepared using electrochemical deposition coupled with self‐assembly accumulation method and characterized with different techniques. The electrochemical behavior and electrocatalytic activity of modified PGEs were investigated. The Ni/Pp‐ABSA/ERGO/PGE showed a unique electrocatalytic oxidation through an Electrochemical‐Chemical (EC’) pathway for methanol in alkaline media (Jpf=7.04 mA cm−2 and Eonest=0.38 V) compared to Ni/PGE, Ni/Pp‐ABSA/PGE and Ni/ERGO/PGE. The obtained results showed that the self‐assembled incorporation of Ni(II) ions in Pp‐ABSA/ERGO film prepared on PGE surface produced a stable modifier with high electrocatalytic activity towards methanol oxidation. In conclusion, the introduced method for the preparation of Pp‐ABSA/ERGO‐based nanocomposites can open a new, cheap and simple way to design a high‐performance electrocatalyst for direct methanol fuel cell systems.

Research on square wave pulsed electrochemical phosphate recovery technology by Pt graphene foam metal electrode

Currently, using electrochemical precipitation techniques for phosphate removal and recovery in hydroxyapatite (HAP) or calcium phosphate (CaP) form is widely used, while the high energy consumption of electrochemical precipitation is a major obstacle to its application. In this study, a square wave pulsed electrochemical phosphate precipitation method was developed, which achieved phosphate pollution control and phosphate resource recovery and reuse at the same time. The square wave pulsed electrochemical phosphate recovery system was constructed and a Pt-rGO/CuF electrode was synthesized and evaluated. This result indicated that the Pt-rGO/CuF electrode had the highest electrocatalytic activity, the better electrical conductivity, and the smallest electron transport barrier. Under optimal operation conditions, the phosphate removal efficiency and specific energy consumption of Pt-rGO/CuF were 64.2% and 21.49 kWh kg−1, respectively. The Pt-rGO/CuF electrode demonstrated the best electrochemical precipitation reaction performance. The Pt-rGO/CuF electrode was applied to multiple types of actual wastewater, and the results showed that it has better application prospects in both low (7.75 mg L−1) and high (66 mg L−1) phosphate concentration wastewater, the phosphate removal efficiency was 75.5% and 59.1%, respectively. Compared with traditional chemical precipitation, the electrochemical precipitation method saved $2.88 per kg P and $57.57 per kg P, respectively.

A highly sensitive self-powered sensing method designed on DNA circuit strategy and MoS2 hollow nanorods for detection of thalassemia

Thalassemia is one of the most common monogenic diseases, which seriously affects human growth and development, cardiovascular system, liver, etc. There is currently no effective cure for this disease, making screening for thalassemia particularly important. Herein, a self-powered portable device with high sensitivity and specificity for efficiently screening of low-level thalassemia is developed which is enabled with AuNPs/MoS2@C hollow nanorods and triple nucleic acid amplification technologies. It is noteworthy that AuNPs/MoS2@C electrode shows the advantages of high electrocatalytic activity, fast carrier migration rate and large specific surface area, which can significantly improve the stability and output signal of the platform. Using high-efficiency tetrahedral DNA as the probe, the target CD122 gene associated with thalassemia triggers a catalytic hairpin assembly reaction to achieve CD122 recycling while providing binding sites for subsequent hybridization chain reaction, greatly improving the detection accuracy and sensitivity of the device. A reliable electrochemical/colorimetric dual-mode assay for CD122 is then established, with a linear response range of 0.0001–100 pM for target concentration and open circuit voltage, and the detection limit is 78.7 aM (S/N = 3); a linear range of 0.0001–10000 pM for CD122 level and RGB Blue value, with a detection limit as low as 58.5 aM (S/N = 3). This method achieves ultra-sensitive and accurate detection of CD122, providing a new method for the rapid and accurate screening of thalassemia.

New insights on the effects of surface facets and calcination temperature on electrochemical properties of MnCo2O4 as bifunctional oxygen electrocatalyst in zinc-air batteries

Metal-air rechargeable batteries are being studied as an alternative to lithium-ion batteries. MnCo2O4 as a ternary mixed metal oxide appeared as a promising oxygen electrocatalyst in metal-air batteries due to relatively high electrocatalytic activity and electronic conductivity. The effects of surface facets and calcination temperature on the electrochemical properties of MnCo2O4 in zinc-air batteries are investigated experimentally and theoretically. The results show that by increasing calcination temperature, the surface facet is changing from the high index {112} to the low index {110}. Concurrently, the oxygen vacancy concentration rises with calcination temperature. Electrochemical results and first principle calculations indicate that the oxygen-deficient {110} facet has superior electrochemical activity over the {112} facet in terms of oxygen evolution reaction and oxygen reduction reaction. These results are essential for designing high performance spinel structured electrocatalyst materials.

Symbiotic study of N-bridged metal complexes as electrocatalysts for hydrogen evolution reaction

Design and fabrication of non-noble metal catalysts for the extensive generation of H2 (hydrogen) gas by water splitting is the upsurging field aiming towards the sustainable environment and need the future clean and green energy. However, scheming and understanding the basic principle regulating the activity of the catalyst is still inexplicable. Although Pt is currently the material of choice owing to its high electrocatalytic activities but need for its high loading and high cost is an intriguing issue needing amicable solution. The hybrid structures of heteroatom-based transition metal complexes are more effective and are cost effective electrocatalysts for hydrogen production. In this proposed work, the electrocatalytic behaviour of alkali (Li+, Na+, K+) and alkaline metal (Ca2+, Sr2+, Ba2+) was figured out along with their synthetic procedure and characterization. Owing to their high complexing ability, ring formation, and bidentate nature, substituted naphthoic acid and aminoguanidine were chosen as bridging ligands. The thermodynamic stability and best catalytic behaviour of synthesized alkali and alkaline earth metals were compared and presented based on electrochemical studies. Linear sweep voltammetry (LSV) curves display excellent activity and Tafel slope was found in the range of 6.38–40 mVdec−1 in 0.5 M H2SO4. The electrochemical impedance spectroscopy (EIS) test was accomplished to recognize the mechanism of HER, and charge transfer resistance was less which indicates that composites are favourable for the hydrogen evolution. The electrochemical surface area (ECSA) was figured by studying the electric double layer capacitance (C dl) and it was found to be 0.377 μFcm2 - 0.143 μFcm2. More prominent ECSA values implies, the target complexes have enhanced electrochemically active/dynamic sites and better hydrogen evolution performance. According to the results, high-performing catalytically active sites are found to be Li [1NA-AMG] metal ions, thus showing a potential method for electrocatalyst engineering. Furthermore, in a volcano plot, the position of the Li [1NA-AMG] metal ions is found to be close to the apex with near thermoneutral catalytic activity. Based on the results, we successfully designed an electrocatalyst as a prospective candidate for hydrogen evolution reaction.