The joint meeting X International Congress of the Mexican Hydrogen Society (MHS) and IV International Congress of Rational and Efficient Use of Energy, was held in Toluca, Mexico, September 27 to October 1, 2010. This was an opportunity for the MHS to host scientific partners that promote the advancement to the hydrogen economy in North and South America. The meeting brought together over 250 delegates from Mexico, Colombia, Brazil, Argentina, USA, Canada, France, Spain and Venezuela. Besides hydrogen technologies, which were the main subject at the event, the meeting included other important topics such as renewables, biomass and biofuels. The joint meeting included 130 oral presentation and short communications. The technical poster session included 25 works presented by MSc and PhD students. The plenary lectures were delivered by Prof. Jeffrey A. Serfass (USA), General Manager of the Partnership for Advancing the Transition to Hydrogen – PATH; Prof. Juan Carlos Bolcich (Argentina), President of Argentinean Hydrogen Association, Member of the International Association for Hydrogen Energy; Prof. Suilma Marisela Fernández Valverde (Mexico), Founder of the Mexican Hydrogen Society, Member of the International Association for Hydrogen Energy; Prof. Odón de Buen Rodríguez (Mexico), expert in areas of energy efficiency, renewable energy and environmental issues; Prof. Electo Eduardo Silva Lora (Brazil), Coordinator of the Universidade Federal de Itajubá (UNIFEI); Prof. Ernestina Torres Reyes (Mexico), President of the Mexican National Association of Solar Energy, Prof. Edgar René Rangel Germán (Colombia), Member of the Colombian National Hydrocarbons Commission. . This issue of the Journal of New Materials for Electrochemical Systems is a compilation of selected papers presented at the meeting. The MHS deeply thanks all authors and reviewers for making this work possible. We also extend special thanks to Prof. O. Savadogo for his important support to MHS throughout these years. The XI Congress of the MHS will take place in Cuernavaca, Mexico, September 21 to 23, 2011. Also, we wish to announce that the joint meeting 9th International Symposium on New Materials and Nano-Materials for Electrochemical Systems and XII International Congress of the Mexican Hydrogen Society will be held in Merida, Yucatan, Mexico, on July 2012. We look forward to seeing you at MHS events (www.smh2.mx).