Hydrogen Production Towards a Carbon-free Economy: A Comprehensive Thermodynamic Analysis

Sustainable hydrogen production is key to achieving zero-emission targets and a hydrogen-based economy. Hydrogen production methods vary in terms of resource, technology, and system efficiency. This work analyzes the thermodynamics of fourteen hydrogen production pathways using Gibbs free energy minimization to examine the effects of pressure (1–60 bar), temperature (100–1000 ◦C), and feed composition, using reactant conversion and product selectivity as key indicators of reaction performance. The impact of simultaneous reactions on hydrogen production is also discussed. From the results, full conversion (100 %), independent of parameter variations at 1 bar pressure, was observed for biomass gasification and steam reforming of glycerol, methanol, ethanol, and bio-oil reactions. However, H2 selectivity in all tested reactions, except for NH3 dissociation and the splitting of water and H2S, is greatly affected by side reactions. Finally, the thermodynamic results of all reactions are compared and validated with published experiments, followed by an evaluation of the challenges and opportunities in hydrogen production. The study provides optimal reaction parameters and a comprehensive comparison of H2 production processes, aiding in designing and developing processes based on regional resource availability. Additionally, it highlights the potential for both local and remote hydrogen production pathways from various renewable energy sources.