Scientific and technological trajectories in electrolyzed hydrogen: The emergence of a green–green hybridization process

Sustainable energy trajectories evolve through processes of knowledge accumulation and recombination within the same trajectory and hybridization between several of them. This paper investigates the emergence of a green hydrogen trajectory by applying a structural main path analysis to both scientific publications and patents related to electrolyzed hydrogen production. Beyond identifying trajectories, we analyze distinct time phases to capture the evolving architecture of the knowledge network. Our findings reveal a clear structural evolution: from an initial phase of competing, parallel paths, through a consolidation phase marked by the dominance of proton exchange membrane (PEM) technologies, to a current phase of hybridization where this core trajectory branches out to integrate with other green technologies (solar, wind, CO 2 -to-methanol). This structural shift reveals empirical signals of an emerging constellation of interrelated sustainable technologies, challenging conventional views on green innovation pathways.