Bimetallic Co-Based (CoM, M = Mo, Fe, Mn) Coatings for High-Efficiency Water Splitting

Abstract

Bimetallic cobalt (Co)-based coatings were prepared by a facile, fast, and low-cost electroless deposition on a copper substrate (CoFe, CoMn, CoMo) and characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffraction analysis. Prepared coatings were thoroughly examined for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution (1 M potassium hydroxide, KOH) and their activity compared to that of Co and Ni coatings. All five coatings showed activity for both reactions, where CoMo and Co showed the highest activity for HER and OER, respectively. Namely, the highest HER current density was recorded at CoMo coating with low overpotential (61 mV) to reach a current density of 10 mA·cm−2. The highest OER current density was recorded at Co coating with a low Tafel slope of 60 mV·dec−1. Furthermore, these coatings proved to be stable under HER and OER polarization conditions.

Synergistically Coupled CoMo/CoMoP Electrocatalyst for Highly Efficient and Stable Overall Water Splitting

“…For comparison, the overpotential of CoMo/CoMoP/NF (104 mV) with greater advantage at 100 mA cm –2 is also shown in Figure b. What is more, the as-prepared CoMo/CoMoP/NF still shows superior activity compared with other recently reported advanced metal/metal phosphide electrocatalysts (Figure h), such as Mo-CoP (40 mV), Co-Mo-B-P/CF (48 mV), CoP/MoP@NC/CC (94 mV), and so on, ,,,,,,− which indicates that this alloy/phosphide heterostructure electrocatalyst has a unique advantage in high HER activity. As expected, Figure c shows that the corresponding Tafel slopes of Pt/C (30.8 mV dec –1 ) are almost equal to the results of previous studies. , The Tafel slope of CoMo/CoMoP/NF is 46.4 mV dec –1 and is lower than those of CoMo/CoMo-LDH/NF, CoMo/NF, CoMoP/NF, CoMo-LDH/NF, and Co-MOF/NF, which reveals that the CoMo/CoMoP/NF undergoes the Volmer–Heyrovsky reaction.…”

Nitrogen Functionalization of CVD Grown Three-Dimensional Graphene Foam for Hydrogen Evolution Reactions in Alkaline Media

“…The band from 1719 cm −1 ascribed to the amide C=O stretching vibration is seen in all the nitrogen-doped samples, and this is related with the COOH groups located at the graphene oxide margins [ 19 , 20 ]. The GrFoam-doped samples present several C-N and N-H vibration modes, i.e., C-N stretching, N-H bending, N-H wagging, and O=C-N bending, corresponding to 1240 cm −1 , 929 cm −1 , 663 cm −1 , and 537 cm −1 , respectively [ 14 , 41 ]. The N-H wagging and O=C-N bending bands were shifted to 666 cm −1 and 584 cm −1 , respectively, for the GrFoam1NPt sample due to the Pt interaction with the GrFoam1N structure.…”

“…According to the Equation (2), during an electrochemical water reduction two electrons are necessary to produce hydrogen gas at the cathode. Depending on the material catalytic activity of the electrode, the HER takes place through two mechanisms, Volmer–Heyrovsky and Volmer–Tafel, as follows [ 41 ]: …”

Dual-Metal Zeolitic Imidazolate Framework Derived Highly Ordered Hierarchical Nanoarrays on Self-Supported Carbon Fiber for Oxygen Evolution

“…In addition, the catalytic effect of a single type of metal is limited, and the introduction of different types of metals to achieve bimetal synergy is an effective means [14]. Nevertheless, achieving a high degree of fusion between the doped metal and the precursor matrix is still a challenging task.…”