Morphological variation of electrodeposited nanostructured Ni-Co alloy electrodes and their property for hydrogen evolution reaction

NiMo–NiCu Inexpensive Composite with High Activity for Hydrogen Evolution Reaction

“…Nickel is the most used cathode material for water electrolysis in alkaline medium, mainly due to its low price and good corrosion resistance. − It has been observed that the catalytic activity of the transition metals increases with the number of d electrons and reaches maximum potential near full electronic filling. , However, the hydrogen evolution rate also depends on the hydrogen adsorption step, which increases as the d orbital electronic filling decreases. It is possible to improve the electroactivity of metals with high d orbital electronic filling to increase the number of vacancies, which can be responsible for strong interaction with electron-donating atoms and adsorb hydrogen by electron pairs formation. , Another way is to combine transition metals that present semifilled d orbitals (Mo, W, and others) with transition metals having pairs of paired electrons (Fe, Co, Ni, and Cu), which show high synergism and excellent catalytic activity for HER applications. ,,− The addition of copper has become an alternative to improve the efficiency of Ni-based catalysts, due to the surface area modification and/or electrocatalytic synergism effect of metal alloying. − For example, Xia et al investigated the catalytic activity of the Ni–Mo–Cu alloy for the hydrogen evolution reaction. The Ni–Mo–Cu alloy showed a 10-fold increase in the film roughness concerning the Ni–Mo alloy.…”

Co-deposition of Co–Ni alloy catalysts from an ethylene glycol system for the hydrogen evolution reaction

“…20 Normally, the excellent HER electrocatalytic activity can be attributed to the signicant synergism in the electrocatalysis because metals of the le half of the transition series with empty or less lled dorbitals (such as Co, Ni or Mo), are alloyed with metals of the right half of the transition series with internally paired dorbitals (such as Co or Ni) that are not available for bonding in the pure metal and that can proceed with denite charge transfer. 46 Importantly, for alkaline H 2 evolution, Co atoms in Moreover, the value of the overpotential (133 mV) for the Co-Ni alloy coating obtained from the EG system is smaller than that of other mainly fabricated nanostructured Co-Ni alloys 11,20,47 and partial Co-Ni alloy composite coatings 48 (Table 1). Meanwhile, in order to obtain valuable information about their HER kinetics, their Tafel curves were extracted from the steady-state polarization curves curves [49][50][51][52] (Fig.…”

“…[7][8][9] That is to say, the reduction of Ni 2+ with a relatively positive initial reduction potential may be inhibited, while the reduction of Co 2+ with a relatively negative initial reduction potential may be promoted during electrodeposition in aqueous systems, and then the molar ratio of Co/Ni in the prepared Co-Ni coatings is greater than that of Co 1), these electrodeposition processes were usually accompanied by an intensive hydrogen evolution reaction (HER), resulting in a profound effect on the current efficiency and quality of the Co-Ni alloy coatings. 3,5,6,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Importantly, a few holes 6,9,11,19,21 and/or microcracks 3,5,16 (as seen in Table 1) could be found on the Co-Ni alloys electrodeposited from aqueous systems, resulting in a profound effect on the catalytic stability for the HER.…”

Electrocatalytic Properties of Co Nanoconical Structured Electrodes Produced by a One-Step or Two-Step Method

“…This effect is connected with the screw dislocation-driven crystal growth [13]. There are several examples of used crystal modifiers such as ethylenediamine dihydrochloride (EDA•2HCl) [15][16][17], CaCl 2 •2H 2 O [13] or NH 4 Cl [18]. This method allows covering a large area quickly.…”