Hydrogen energy has emerged as a strategic option for decarbonizing transport segments that are difficult to electrify directly. Yet the integrated intellectual structure, collaboration networks, thematic evolution, and emerging digital frontiers of this rapidly expanding research field remain insufficiently characterized. This study addresses that gap through a comprehensive sciento- metric analysis of 1,699 Scopus-indexed journal articles on hydrogen energy in transportation published between 2000 and 2025. An integrated multi-tool workflow comprising Bibliometrix, VOSviewer, and Python with cross-tool validation is employed. Results reveal a compound annual growth rate of 18.82%, with China, Germany, and the United Kingdom as the principal research contributors. Three dominant knowledge clusters are identified: hydrogen production and storage infrastructure (Technology Readiness Level 4 to 8), fuel cell vehicle technologies and energy management (TRL 6 to 9), and electric and hydrogen-electric hybrid system integration (TRL 4 to 9). Keyword burst analysis identifies an emerging digital convergence frontier. Green hydrogen, machine learning, and digital twin are the fastest-growing terms in the 2021 to 2025 period. Blockchain, IoT, and quantum computing also show notable keyword growth, though their absolute frequencies remain low and are treated as prospective research directions. The findings are contextualized against documented techno-economic progress, including boundary- dependent electrolyzer cost-reduction pathways and uneven hydrogen-refueling infrastructure deployment. The study advances a systems-integration perspective. This field has matured from isolated component studies into an interconnected knowledge system spanning production, infrastructure, vehicle technology, and digital intelligence. The findings offer actionable implications for researchers, engineers, and policymakers advancing the global hydrogen transition
Hassan et al. (Fri,) studied this question.