A high-efficiency oxygen evolution electrode material of a carbon material containing a NiCo bimetal

Electrocatalytic activity of electrodeposited CoOx thin film on low-carbon unalloyed steel substrate toward electrochemical oxygen evolution reaction (OER)

In this study, we report elaboration of a thin film of CoOx on a low carbon unalloyed steel substrate by electrochemical route and the study of its electrocatalytic performances with respect to the evolution reaction of oxygen (OER) in NaOH medium. The elaborated deposits were well-characterized using X-ray diffraction. Kinetic and thermodynamic parameters such as exchange current density, Tafel slope, reaction order with respect to OH- ions and apparent activation energy were studied. The CoOx displays satisfactory OER performance in an alkaline medium, with a low overvoltage of 362 mV at 10 mA/cm2 and a Tafel slope of 81 mV/dec at 293 K. The apparent kinetic activation energy (= 29.79 kJ/mol) was similar to those obtained for the reported catalytic electrode materials. The O2 gas obtained on the cobalt oxide electrode was 2.865 mmol/s.cm2, which is 28 times higher than that obtained for the platinum electrode (0.102 mmol/s.cm2). Chronoamperometry demonstrates a better electrochemical stability under a polarization potential of 2 V in 1 M NaOH for nearly 25 h. The low cost, the high OER performance, as well as the good stability of the CoOx electrode make it a promising candidate for the industrial-scale water electrolysis.

Molten Salts Approach of Poly(vinyl alcohol)-Derived Bimetallic Nickel-Iron Sheets Supported on Porous Carbon Nanosheet as an Effective and Durable Electrocatalyst for Methanol Oxidation

The preparation of metallic nanostructures supported on porous carbon materials that are facile, green, efficient, and low-cost is desirable to reduce the cost of electrocatalysts, as well as reduce environmental pollutants. In this study, a series of bimetallic nickel-iron sheets supported on porous carbon nanosheet (NiFe@PCNs) electrocatalysts were synthesized by molten salt synthesis without using any organic solvent or surfactant through controlled metal precursors. The as-prepared NiFe@PCNs were characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction, and photoelectron spectroscopy (XRD and XPS). The TEM results indicated the growth of NiFe sheets on porous carbon nanosheets. The XRD analysis confirmed that the Ni_1-xFe_x alloy had a face-centered polycrystalline (fcc) structure with particle sizes ranging from 15.5 to 30.6 nm. The electrochemical tests showed that the catalytic activity and stability were highly dependent on the iron content. The electrocatalytic activity of catalysts for methanol oxidation demonstrated a nonlinear relationship with the iron ratio. The catalyst doped with 10% iron showed a higher activity compared to the pure nickel catalyst. The maximum current density of Ni_0.9Fe_0.1@PCNs (Ni/Fe ratio 9:1) was 190 mA/cm² at 1.0 M of methanol. In addition to the high electroactivity, the Ni_0.9Fe_0.1@PCNs showed great improvement in stability over 1000 s at 0.5 V with a retained activity of 97%. This method can be used to prepare various bimetallic sheets supported on porous carbon nanosheet electrocatalysts.

Bimetallic MOFs-Derived Hollow Carbon Spheres Assembled by Sheets for Sodium-Ion Batteries

Metal-organic frameworks (MOFs) have attracted extensive attention as precursors for the preparation of carbon-based materials due to their highly controllable composition, structure, and pore size distribution. However, there are few reports of MOFs using p-phenylenediamine (pPD) as the organic ligand. In this work, we report the preparation of a bimetallic MOF (CoCu-pPD) with pPD as the organic ligand, and its derived hollow carbon spheres (BMHCS). CoCu-pPD exhibits a hollow spherical structure assembled by nanosheets. BMHCS inherits the unique hollow spherical structure of CoCu-pPD, which also shows a large specific surface area and heteroatom doping. When using as the anode of sodium-ion batteries (SIBs), BMHCS exhibits excellent cycling stability (the capacity of 306 mA h g^-1 after 300 cycles at a current density of 1 A g^-1 and the capacity retention rate of 90%) and rate capability (the sodium storage capacity of 240 mA h g^-1 at 5 A g^-1). This work not only provides a strategy for the preparation of pPD-based bimetallic-MOFs, but also enhances the thermal stability of the pPD-based MOFs. In addition, this work also offers a new case for the morphology control of assembled carbon materials and has achieved excellent performance in the field of SIBs.

Ultrathin Two-Dimensional Bimetal-Organic Framework Nanosheets as High-Performance Electrocatalysts for Benzyl Alcohol Oxidation

Ultrathin two-dimensional metal-organic frameworks (2D MOFs) have the potential to improve the oxidation of benzyl alcohol (BA) with a large surface area and open catalytic active sites. To achieve high-efficiency electrocatalysts for the oxidation of benzyl alcohol, a moderate solvothermal method was evolved to synthesize a series of 2D MOFs on nickel foam (Ni-MOF/NF, NiCo-61-MOF/NF, NiCo-21-MOF/NF). As the electrocatalyst used for the oxidation of benzyl alcohol, NiCo-61-MOF/NF presented a lower overpotential and superior chemical durability than other electrocatalysts; it only required a potential of ∼1.52 V (vs RHE) to reach 338.16 mA cm^-2, with an oxidation efficiency of more than 86%. Besides, after continuous electrocatalysis for 20 000 s at 1.42 V (vs RHE), the current density of NiCo-61-MOF/NF nanosheets was still 38.67 mA cm^-2 with 77.34% retention. This demonstrated that NiCo-61-MOF/NF nanosheet electrocatalysts had great potential for benzyl alcohol oxidation. From both the experimental and theoretical studies, it was discovered that NiCo-61-MOF/NF nanosheets have the highest electrocatalytic activity due to their distinctive ultrathin 2D structure, optimized electron structure, and more accessible active sites. This finding would pave a brand-new thought for the design of electrocatalysts with electrocatalytic activity for benzyl alcohol oxidation (EBO).

A Fe-doped Co-oxide Electrocatalyst Synthesized Through Post-Modification Method Toward Advanced Water Oxidation

In the context of the ever-increasing energy crisis, electrocatalytic water splitting has attracted widespread attention as an effective means to provide clean energy. However, the oxygen evolution reaction (OER), which...

Formation of NiFe-MOF nanosheets on Fe foam to achieve advanced electrocatalytic oxygen evolution

2D bimetal metal organic frameworks (MOFs) are recognized as one of the most promising electrocatalysts for oxygen evolution reaction (OER). Herein, a facile approach was proposed to construct NiFe-MOF nanosheets...