Characterization of Ni, NiMo, NiW and NiFe electroactive coatings as electrocatalysts for hydrogen evolution in an acidic medium

• Published in: Journal of molecular catalysis. A, Chemical Chemical, 2005-02, Vol.226 (2), p.179-197
• Main Authors: Navarro-Flores, Elisa, Chong, Zhiwen, Omanovic, Sasha
• Format: Article
• Language: English
• Subjects: Acidic medium; Catalysis; Chemistry; Electrocatalytic coatings; Electrochemistry; Exact sciences and technology; General and physical chemistry; Hydrogen; Kinetics and mechanism of reactions; Nickel-based alloys; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Water electrolysis
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/j.molcata.2004.10.029

The paper reports a study on the influence of alloying nickel by left-hand side transition metals (Fe, Mo, W) on the electrocatalytic activity in hydrogen evolution in an acidic environment. A number of experimental techniques were used in research (dc and ac electrochemical techniques, XRD, SEM, EDS, and ICP). The results clearly demonstrate that alloying nickel with Fe, Mo or W results in an increased electrocatalytic activity in hydrogen evolution when compared to pure nickel. Two effects were found to be responsible for the observed behavior; an increase in surface roughness and intrinsic activity of the material. Ni 7.3Mo was found to yield the highest overall electrocatalytic activity among the investigated materials mainly due the highest surface roughness, while Ni 3.4W was found to yield the highest intrinsic electrocatalytic activity, which is explained on the basis of the modification of electron density in d-orbitals upon alloying nickel with tungsten. It was also noticed that an increase in crystallinity can contribute to an increased electrocatalytic activity in hydrogen evolution. The kinetics of electrochemical hydrogen evolution in an acidic medium is enhanced by alloying Ni with a left-hand side transition metal. Two effects were found to be responsible for the observed behavior: (i) an increase in surface roughness and (ii) an increase in intrinsic activity of the material due to the modification of electron density in d-orbitals upon alloying. ▪ Electrocatalytic activity of Ni-based catalysts for hydrogen evolution at overpotential −150 mV expressed in terms of the overall activity (normalized to the apparent surface area of the catalyst) and intrinsic activity (normalized to the true surface area of the catalyst).