Synthesis and characterization of Au-modified macroporous Ni electrocatalysts for alkaline water electrolysis

Abstract

Au nanoparticles (Au-NPs) were successfully synthesized and incorporated into the surface of a macroporous Ni electrode fabricated via galvanostatic electrodeposition at high current densities in order to produce hydrogen by means of alkaline water electrolysis. The developed electrodes were morphologically characterized by means of confocal laser scanning and field emission scanning electron microscopes. The electrocatalytic behaviour towards the hydrogen evolution reaction was studied by Tafel polarization curves and electrochemical impedance spectroscopy. It was clear that enlarging the real surface area of an electrode its catalytic activity was greatly enhanced. This improvement was further increased when Au-NPs were added to the macroporous Ni surface. In this case, the improvement was not only caused by enlarging the surface area but also by an improvement in the intrinsic catalytic activity of the alloy, as it was shown by the exchange current densities values, calculated from the real surface area.

Gold-supported activated NiZn coatings: hydrogen evolution and corrosion studies

“…The modification of NiZn surface by Au leads to a facile discharge process and highest current densities. The reduction in the -η 100 at this electrode is 69% (with respect to the Cu/Ni/NiZn), which demonstrates that the presence of Au on the catalyst surface favours the hydrogen evolution kinetics and reduces the energy input for activating the HER [23,24]. The Au-modified electrode exhibits the highest i -1.250 , i o and α, which are directly proportional to the rate of the HER (Table II) [22].…”

“…The Au-modified electrode exhibits the highest i -1.250 , i o and α, which are directly proportional to the rate of the HER (Table II) [22]. The reduction in the -η 100 at this electrode is 69% (with respect to the Cu/Ni/NiZn), which demonstrates that the presence of Au on the catalyst surface favours the hydrogen evolution kinetics and reduces the energy input for activating the HER [23,24]. The lower overpotential, the lower energy required to produce a given amount of hydrogen gas, that is, the higher the catalytic activity of the electrode [24].…”

“…All the semi-logarithmic polarization curves (Figure 2b) show a typical Tafel behaviour indicates that the HER is kinetically controlled [5,21]. The lower overpotential, the lower energy required to produce a given amount of hydrogen gas, that is, the higher the catalytic activity of the electrode [24]. The reduction in the -η 100 at this electrode is 69% (with respect to the Cu/Ni/NiZn), which demonstrates that the presence of Au on the catalyst surface favours the hydrogen evolution kinetics and reduces the energy input for activating the HER [23,24].…”

“…The CPE 1 À R 1 and CPE 2 À R 2 correspond to the high-frequency and lowfrequency loops, respectively. On contrary, the diameter of the second low-frequency loop decreases with the increasing potential, which indicates that the adsorption process facilitates and the charge-transfer process dominates the impedance response [24]. The CPE values related to the HER kinetics greatly increased after the modification of the surface by the Au deposition points to its greater electrochemical accessible surface area, being a result of electrodeposition of gold.…”

“…The Au-modified electrode exhibits the highest i -1.250 , i o and α, which are directly proportional to the rate of the HER (Table II) [22]. Gold was Gold-supported activated NiZn coatings: HER and corrosion studies R. Solmaz reported to be a poor electrocatalyst for the HER because of the weak bond with H; namely, this metal is a poor substrate for hydrogen adsorption [12,24]. The lower overpotential, the lower energy required to produce a given amount of hydrogen gas, that is, the higher the catalytic activity of the electrode [24].…”