Search

To design and construct bifunctional electrocatalyst with high activity is important to the commercial development of electrochemical water splitting (EWS) technology. The carbon clothe (CC) supported on Ni(OH) 2 nanosheet is used as template to tune the morphology of Ni 0.85 Se. To improve the activity of Ni 0.85 Se, amorphous Ni 4 Mo alloy is anchored on the Ni 0.85 Se to obtain the Ni 0.85 Se/Ni 4 Mo catalyst (NS/NM) by electrodeposition method. The electron state and conductivity of NS/NM are modulated compared to that of the NS sample. It is found that the electron transfers from Ni 4 Mo to Ni 0.85 Se. Benefiting from the tuned electron state of Ni 0.85 Se and Ni 4 Mo, the enhanced number of exposed active sites and lower R ct value, the NS/NM heterostructure electrode requires low overpotentials of 51 and 206 mV to obtain 10 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The optimized electrode shows fast kinetics and exhibits near to 100% Faraday efficiency for HER and OER in 1 M KOH. Importantly, it is noted that the electrocatalytic activity of NS/NM catalyst for both HER and OER is enhanced obviously in comparison with NS sample. With heterostructure catalyst, the EWS only proceeds at 1.48 V to yield 10 mA cm−2, which is reduced about 110 mV compared to NS electrode. Here, a novel kind of bifunctional heterostructure electrocatalyst is constructed. [Display omitted] • The heterostructure of crystalline Ni 0.85 Se anchored on amorphous Ni 4 Mo alloys was prepared. • The formation of heterostructure causes the redistribution of electrons. • The introduction of Ni 4 Mo enhances the activity for HER and OER obviously. • With heterostructure catalyst, the EWS only proceeds at 1.48 V to yield 10 mA cm−2. [ABSTRACT FROM AUTHOR]

In the study, the electrodeposition mechanism of Ni–Mo alloy was investigated. Potentiostatic deposition showed that the presence of MoO 4 2− could reduce the deposition overpotential of Ni, and the deposition current efficiency of Ni–Mo alloy was lower than pure Ni deposition as the potential moved negatively. Cyclic Voltammetry (CV) indicated that both the first reduction peak for Ni deposition and the deposition peak of Ni–Mo alloy moved to more positive potentials as the content of Ni 2+ increased, but the deposition peak of Ni–Mo alloy moved to more negative potentials as the content of MoO 4 2− increased. The cathodic polarization curve on Rotating Disc Electrode (RDE) presented that Ni–Mo codeposition was controlled by charge transfer. The morphology, composition and structure of Ni–Mo alloy were characterized by SEM, EDS and XRD. The results showed the Ni–Mo alloy coatings exhibited a spherical and cauliflower-like pattern, having a considerably rougher surface, with nano-crystal structure when the elements composition was Ni 80.14 Mo 19.59 . The electrochemical activity for hydrogen evolution of Ni–Mo alloy was studied in 30 wt.% KOH at 25 °C using steady-state polarization and electrochemical impedance spectroscopy (EIS) methods. The results clearly demonstrated that an increase in the electrochemical activity for hydrogen evolution of the Ni–Mo alloy coating can be attributed both higher exchange current density and larger real electrode area. [ABSTRACT FROM AUTHOR]

Abstract: Enhancement of catalytic activity of Ni–Mo alloy for hydrogen evolution reaction (HER) has been observed when the alloy is electrodeposited under magnetic field, B control. Using cyclic voltammetry at low scan rate and electrochemical impedance spectroscopy (EIS) measurements, the significant modification of the activity of the alloy has been characterized in acidic and in basic water at 25 °C and in 33% NaOH solution at 85 °C. For the deposit obtained with B, the polarization curves show high current densities values (about 50% higher then without B), low ohmic drop and overpotential shift to noble way more then 100 mV. EIS measurements show a low polarization resistance and a high double layer capacitance for the alloy deposited under magnetic field control. In basic media, with or without B, the EIS measurements exhibit a supplementary inductive type relaxation. [Copyright &y& Elsevier]

Abstract: The amorphous Ni–Mo film with high HER (hydrogen evolution reaction) activity was obtained by pulse plating. The optimum electrodeposition conditions with respect to HER overpotential were determined, e.g. Na2MoO4·2H2O concentration, current density and duty cycle. Correspondingly, the compositions and components of the Ni–Mo coatings with various molybdenum contents were investigated systematically. The results showed that when the ratio of nickel and molybdenum concentrations in the electrodeposition bath is lower than 1 (mol%), the molybdenum content in the coating decreases with the increasing Na2MoO4·2H2O concentration, while the corresponding HER overpotential of the Ni–Mo film increases. The amorphous Ni–Mo coating was obtained when the molybdenum content was c.a. 30 mass%, which shows high HER activity (η 200 =62mV at 200mAcm−2 and 80°C) and excellent corrosion resistance. After galvano-static electrolysis for 100h in 33 mass% NaOH solution, the amorphous structure was destroyed due to the dissolution of molybdenum. [Copyright &y& Elsevier]

Abstract: The hydrogen evolution reaction on the electrodeposited Ni–Mo alloy coatings, as well as their electrochemical properties in the NaOH solutions, have been investigated by the polarization measurements, cyclic voltammetry and EIS technique. It was shown that the Ni–Mo alloy coatings electrodeposited from the pyrophosphate-sodium bicarbonate bath possess high catalytic activity for hydrogen evolution in the NaOH solutions. Their stability in the 1M NaOH at 25°C under the condition of the reverse polarization was shown to be very good, while in the 33% NaOH at 85°C (conditions of the industrial electrolysis) the electrodeposited Ni–Mo alloy coatings exhibited also high catalytic activity, but low stability, as a consequence of a deterioration of the alloy coatings. [Copyright &y& Elsevier]