Research Information System
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, vol.178, 2025 (SCI-Expanded, Scopus)
This study investigates the environmental implications of hydrogen energy and transportation-related energy efficiency R&D expenditures within the framework of the environmental Kuznets curve (EKC) and the load capacity curve (LCC) hypotheses. The analysis focuses annual data from 2009 to 2023 for ten European countries by using the Augmented Mean Group (AMG) and the Half Panel Jackknife (HPJ) estimators. The outcomes reveal that while energy efficiency R&D in transport significantly reduces CO2 emissions, hydrogen-related R&D has no statistically significant effect on emissions, but has a positive and significant effect on the load capacity factor (LCF). These divergent environmental effects of hydrogen-versus transport-focused R&D underscore the limitations of emission-only metrics and highlight the LCF's value as a holistic sustainability indicator. Furthermore, the findings indicate a rejection of the EKC hypothesis, as no statistically significant inverted U-shaped relationship was observed between GDP growth and CO2 emissions. Conversely, the results confirm the LCC, which indicates an improvement in environmental quality, as measured by the LCF, at higher income levels. The study offers an important policy implication: investments in hydrogen R&D may not lead to immediate emission reductions, but can strengthen ecological resilience in the long run. Hence, policymakers should adopt multidimensional environmental indicators and prioritize sector-specific R&D funding to support comprehensive, crosssector sustainability transitions (i.e., coordinated shifts in policy, technology, and investment changes across energy and transport systems).