Scalable Molten Salt Synthesis of Platinum Alloys Planted in Metal–Nitrogen–Graphene for Efficient Oxygen Reduction

Understanding Synergistic Catalysis on Cu-Se Dual Atom Sites via Operando X-ray Absorption Spectroscopy in Oxygen Reduction Reaction

The construction and understanding of synergy in well-defined dual-atom active sites is an available avenue to promote multistep tandem catalytic reactions. Herein, we construct a dual-hetero-atom catalyst that comprises adjacent Cu-N₄ and Se-C₃ active sites for efficient oxygen reduction reaction (ORR) activity. Operando X-ray absorption spectroscopy coupled with theoretical calculations provide in-depth insights into this dual-atom synergy mechanism for ORR under realistic device operation conditions. The heteroatom Se modulator can efficiently polarize the charge distribution around symmetrical Cu-N₄ moieties, and serve as synergistic site to facilitate the second oxygen reduction step simultaneously, in which the key OOH*-(Cu₁ -N₄ ) transforms to O*-(Se₁ -C₂ ) intermediate on the dual-atom sites. Therefore, this designed catalyst achieves satisfied alkaline ORR activity with a half-wave potential of 0.905 V vs. RHE and a maximum power density of 206.5 mW cm^-2 in Zn-air battery.

Alumina supported copper oxide nanoparticles (CuO/Al2O3) as high-performance electrocatalysts for hydrazine oxidation reaction

Direct hydrazine liquid fuel cell (DHFC) is perceived as effectual energy generating mean owing to high conversion efficiency and energy density. However, the development of well-designed, cost effective and high performance electrocatalysts is the paramount to establish DHFCs as efficient energy generating technology. Herein, gamma alumina supported copper oxide nanocatalysts (CuO/Al₂O₃) are synthesized via impregnation method and investigated for their electrocatalytic potential towards hydrazine oxidation reaction. CuO with different weight percentages i.e., 4%, 8%, 12%, 16% and 20% are impregnated on gamma alumina support. X-ray diffraction analysis revealed the cubic crystal structure and nanosized particles of the prepared metal oxides. Transmission electron microscopy also referred to the cubic morphology and nanoparticle formation. Electrochemical oxidation potential of the CuO/Al₂O₃ nanoparticles is explored via cyclic voltammetry as the analytical tool. Optimization of conditions and electrocatalytic studies shown that 16% CuO/Al₂O₃ presented the best electronic properties towards N₂H₂ oxidation reaction. BET analysis ascertained the high surface area (131.2546 m² g¹) and large pore diameter (0.279605 cm³ g^-1) for 16% CuO/Al₂O₃. Nanoparticle formation, high porosity and enlarged surface area of the proposed catalysts resulted in significant oxidation current output (600 μA), high current density (8.2 mA cm^-2) and low charge transfer resistance (3.7 kΩ). Electrooxidation of hydrazine on such an affordable and novel electrocatalyst opens a gateway to further explore the metal oxide impregnated alumina materials for different electrochemical applications.

MnCo2O4/NiCo2O4/rGO as a Catalyst Based on Binary Transition Metal Oxide for the Methanol Oxidation Reaction

The demands for alternative energy have led researchers to find effective electrocatalysts in fuel cells and increase the efficiency of existing materials. This study presents new nanocatalysts based on two binary transition metal oxides (BTMOs) and their hybrid with reduced graphene oxide for methanol oxidation. Characterization of the introduced three-component composite, including cobalt manganese oxide (MnCo₂O₄), nickel cobalt oxide (NiCo₂O₄), and reduced graphene oxide (rGO) in the form of MnCo₂O₄/NiCo₂O₄/rGO (MNR), was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray (EDX) analyses. The alcohol oxidation capability of MnCo₂O₄/NiCo₂O₄ (MN) and MNR was evaluated in the methanol oxidation reaction (MOR) process. The crucial role of rGO in improving the electrocatalytic properties of catalysts stems from its large active surface area and high electrical conductivity. The alcohol oxidation tests of MN and MNR showed an adequate ability to oxidize methanol. The better performance of MNR was due to the synergistic effect of MnCo₂O₄/NiCo₂O₄ and rGO. MN and MNR nanocatalysts, with a maximum current density of 14.58 and 24.76 mA/cm² and overvoltage of 0.6 and 0.58 V, as well as cyclic stability of 98.3% and 99.7% (at optimal methanol concentration/scan rate of 20 mV/S), respectively, can be promising and inexpensive options in the field of efficient nanocatalysts for use in methanol fuel cell anodes.

In Situ Nitrogen Functionalization of 2D-Ti3C2Tx-MXenes for High-Performance Zn-Ion Supercapacitor

Zinc (Zn) ion supercapacitors (ZISCs) have attracted considerable attention as a viable energy storage technology because they are cost-effective, safe, and environmentally friendly. However, cathode materials with suitable properties are rare and need to be explored. In this regard, metal carbides (MXenes) are a good choice for capacitive energy storage, but they exhibit low capacitance. The energy storage performance of MXenes can be bossed using functionalization with heteroatom doping, e.g., nitrogen (N), to simultaneously modify ZISCs’ fundamental characteristics and electrochemical properties. Herein, we present an in-situ N-functionalization of Ti₃C₂T_x-MXene via a hydrothermal reaction with urea (denoted as N-Ti₃C₂T_x-MXene). N-functionalization into Ti₃C₂T_x-MXene raised Ti₃C₂T_x-MXene’s interlayer spacing and boosted the Zn-ion storage in 1 M ZnSO₄ electrolyte. The N-Ti₃C₂T_x-MXene electrode delivered an excellent specific capacitance of 582.96 F/g at 1 A/g and retained an outstanding cycle stability of 94.62% after 5000 cycles at 10 A/g, which is 1.8 times higher than pristine Ti₃C₂T_x-MXene at identical conditions. Moreover, the N-Ti₃C₂T_x-MXene//Zn device demonstrated a maximum capacitance of 153.55 F/g at 1 A/g, retained 92% of its initial value after 5000 cycles, and its Coulombic efficiency was ~100%. This strategy considerably reduced Ti₃C₂T_x-MXene nanosheet restacking and aggregation and enhanced electrochemical performance. Further, this research elucidated N-Ti₃C₂T_x-MXene’s charge–storage process and offered a fresh approach to the rational design of novel electrode materials for ZISCs.

Poisoning Effects of Cerium Oxide (CeO2) on the Performance of Proton Exchange Membrane Fuel Cells (PEMFCs)

In this study, the poisoning effects of cerium oxide (CeO2) as the contaminant on the performance of proton exchange membrane fuel cells (PEMFCs) are evaluated. An experimental setup was developed to analyze the performance characteristic (I-V) curves in contaminated and non-contaminated conditions. Focused ion-beam scanning electron microscopy (FIB-SEM) cross-section images were obtained as an input for the energy dispersive X-ray (EDX) analysis. The results of the EDX analysis verified the presence of CeO2 in the contaminated membrane electrode assembly (MEA), in addition to fluorine and sulfur. EDX analysis also revealed that as a result of CeO2 contamination, sulfur and fluorine would be distributed all around the MEA, instead of being only in the membrane. The results illustrate that hydrofluoric acid (HF), sulfuric acid (H2SO4), and fluorinated polymer fragments are released, which enhance the crossover of the reactant gases through the membrane, hence reducing the cell’s performance. The I-V characteristic curves proved that the non-contaminated PEMFC setup had double the performance of the contaminated PEMFC.