113 Hydrogen, as a high-quality clean and renewable energy re- source, is increasingly considered as one of the most promising candidates for the fuel of the future [1,2]. Hydrogen evolution reaction (HER) in aqueous solution is one of the most often studied electrode reactions [3,4]. During the last decades, it has been well established that (HER) occurs via two successive elementary events. The initial discharge of hydrogen ions to adsorbed monoatomic hydrogen (equation 1) [5]. Followed by the chemical (equation 2) or electrochemical (equation 3) recombination of monoatomic hydrogen to molecular hydrogen. (1) (2) (3) It is well known that water electrolysis is an important technique for hydrogen generation [6]. Although, water electrolysis is not the cheapest method of hydrogen production, it supplies hydrogen of a very high purity in large quantity. Unfortunately, the high energy consumption mainly caused by HER overpotential restrains its application at the present days [7]. One proposed alternative to solve this problem is to use noble metals (such as Pt, Au) as cath- ode materials for the HER [8]. However, these metals are not only expensive, actually the platinum and gold worldwide reserves are limited [9]. On the other hand, other metallic electrodes such as steels are commonly employed for water electrolysis but these are very sus- ceptible to corrosion effects and consequently their life time is decreased [1]. In this sense, other authors have proposed the use of new and cheap cathode materials resistant to corrosion, for exam- ple: the aluminum, Inconel alloys and glassy carbon, however the latter has a very low electrical conductivity, therefore the energy consumption is high [5]. Furthermore, the temperature is one of the variables that strongly affects the corrosion behavior of metal- lic materials and is widely studied in corrosion investigations and for that reason this variable is also studied in this research [10-15]. Another alternative to reduce the corrosion effects relies on the protection of steel cathodes against corrosion employing the iron *To whom correspondence should be addressed: Email: juan.fuentes@cinvestav.edu.mx Phone: 8444389600, Ext 8512 A Kinetic Study of The Hydrogen Evolution Reaction in Phosphoric Acid Solutions with Iron and Manganese Phosphatized Steel Cathodes G. Alvarado-Macías, J.C. Fuentes-Aceituno * and A. Salinas-Rodríguez Centro de Investigación y de Estudios Avanzados del IPN, Unidad Saltillo, Av. Industria Metalúrgica # 1062, Parque Industrial Ramos Arizpe, Ramos Arizpe, Coahuila, 25900, México. Received: October 31, 2013, Accepted: February 12, 2014, Available online: April 15, 2014 Abstract: In this investigation a kinetic study of the HER was carried out employing a steel rotating disk with different aqueous solutions containing Phosphoric Acid (H 3 PO 4 ) with or without metallic manganese (Mn) and Nitric Acid (HNO 3 ). Furthermore, the HER was evalu- ated on iron and manganese phosphate coatings. Analyses of Tafel plots and the charge transfer coefficients, revealed one electrical poten- tial zone where the monoatomic hydrogen can be recombined electrochemically to H 2 as the rate determining step, with charge transfer coefficients similar to an activationless process (α→0). On the other hand, an increase in the concentration of H 3 PO 4 promotes a higher exchange current for the HER. The Mn in the aqueous solutions has a catalytic effect on the hydrogen generation rate at room tempera- ture. However, the precipitation of Mn 3 (PO 4 ) 2 on steel decreases the HER kinetics at high temperatures. These observations are also sup- ported with SEM (Scanning Electron Microscopy) characterizations. Keywords: Polarization, Tafel, monoatomic hydrogen, HER. Journal of New Materials for Electrochemical Systems 17, 113-122 (2014) © J. New Mat. Electrochem. Systems