Toward Large-Scale Hydrogen Production from Water: What Have We Learned and What Are the Main Research Hurdles to Cross for Commercialization?

The focus of this study is evaluating the status of the most promising methods for water splitting to H₂ and O₂ with their implementation in mind. These are thermochemical water splitting, photocatalytic (PC) and photo-electrocatalytic (PEC) water splitting, and water electrolysis. In addition to evaluating their coherence, potential, and cost, some misconceptions in the PC H₂ production from water over suspended powder catalysts are highlighted. A few needed research directions at the fundamental level together with the main hurdles to cross for large-scale production are presented and in some cases discussed. Although an increasing level of activity has taken place in the last few years for large-scale hydrogen production from water, this is still marginal (at the megawatt scale). A considerable investment in different technologies is needed for a noticeable impact on the environment to occur with an objective to decrease the world dependence on fossil fuels (the terrawatt scale).