From Grey to Green and from West to East: The Geography and Innovation Trajectories of Hydrogen Fuel Technologies

Despite the potential of hydrogen as a sustainable energy carrier, existing studies analysing the recent evolution of this technology are scattered, typically focusing on a specific type of hydrogen technology within a single country or region. In this paper, we adopt a broader perspective, providing an overview of the evolution of knowledge generation across different types of hydrogen fuel, and the leading countries in developing new technologies in this field. Using data from the European Patent Office, we map knowledge generation on hydrogen fuel technologies, exploring its geographic distribution and its link with environmental sustainability. While the United States leads the generation of new knowledge, other Asian and European countries show greater dynamism in growth and specialisation. Our study shows that although hydrogen fuel is considered environmentally friendly, most recent technological developments are still related to fossil energy sources. However, a faster growth rate is observed in the knowledge of hydrogen fuel from renewable sources, pointing to a promising path towards sustainability. Moreover, our analysis of the knowledge interconnection between different hydrogen types suggests that those technologies developed for hydrogen based on fossil energy sources have enabled novel applications based on renewable energies.