Hydrogen production: current state and future trajectories of development

Hydrogen can act as a low-carbon energy carrier, but its climate benefit depends on the production pathway, energy source, and system boundary. This review synthesizes recent progress (2020–2025) in hydrogen production technologies, covering thermochemical routes (steam methane reforming (SMR) with/without carbon capture and storage (CCS)), water electrolysis (alkaline, proton exchange membrane (PEM), and solid oxide electrolysis (SOEC)), and emerging photo-, bio-, and ultrasound-assisted pathways. To move beyond a descriptive catalog, the technologies are benchmarked using consistent criteria including technology readiness level (TRL), scalability constraints, key technical bottlenecks, and levelized cost of hydrogen (LCOH). Energy efficiencies are reported on a lower heating value (LHV) basis where available and explicitly labeled otherwise. For SOEC in particular, the highest reported LHV efficiencies typically assume high-temperature steam operation and system-level heat integration; accordingly, whenever SOEC efficiency values are discussed, the accounting boundary (electricity-only vs. electricity + heat) is stated to avoid misinterpretation.3. The analysis highlights near-term supply realities and the conditions required for deep decarbonization, while identifying prioritized research trajectories in catalyst durability, system-level heat and mass integration, standardized reporting of energy and cost metrics, and robust life-cycle assessment.