Economical sustainability of green hydrogen production depends not only on electrodes composition and durability, reactor materials, stability or balance of system, but very importantly on the cost of the renewable energy needed for its fabrication. Thus, for an ideal electrocatalytic water splitting system working at 1.5V with a electricity cost of 23 €/MWh, a level achievable in sunny countries below parallel 40º through solar energy, the electrical cost of hydrogen is 0.92 €/Kg, assuming 100% faradaic efficiency. If low cost and long-lasting reactors and associated processing units are able of reducing the cost of the balance of system to ~ 0.38 €/kg, the total cost of the hydrogen production rises to 1.3 €/kg. This optimal configuration, that improves the 2.4-5.7 €/kg costs reported until now,[1] is still a 30% above the 1.0 €/kg obtained from the conventional steam gas reforming processes in the past years. The large increase of natural gas price, due to recent geopolitical turbulences and the rising tendency of the cost of CO₂ emission rights, compromises the achievement of this last price in the next future, what gives green hydrogen a chance to be competitive in a near future.

Still, the need of huge amounts of low cost hydrogen to decarbonise our society requires that the 1.0 €/Kg floor price is broken to even lower values even if the ideal conditions stated above are not achieved. One way to reach this objective is substituting the low value oxygen anodic reaction by an oxidation that produces chemicals of interest for the industry. In such a way, the theoretical total price reduces by half for the same energy consumption to 0.65€/kg, far below the objective price. Hydrogen prices can be further reduced if the materials produced in the oxidation reaction have a high added value enough to balance its cost. Here a sample reaction, simultaneous electrochemical production of hydrogen and 2,5 furandicarboxilic acid (FDCA) is shown. FDCA is a precursor of polyethylene furanoate (PEF) which is called to substitute polyethylene terephthalate (PET), obtained from the oxidation of 5-hydroxymethylfurfural (HMF) which is obtained from biomass. The electro oxidation of HMF is produced in using easily made and inexpensive NiO-OH electrodes, obtained by Ni electrodeposition on pencil graphite rods (Ni/PGR). [2,3]

References:

[1] https://home.kpmg/xx/en/home/insights/2020/11/the-hydrogen-trajectory.html#:~:text=Cost%20of%20green%20hydrogen%20from,is%20cost%2Dcompetitive%20with%20blue

[2] DOI: 10.1039/D1GC02031E L. Gouda, L. Sévery, T. Moehl, E. Mas-Marzá, P. Adams, F. Fabregat-Santiago and S. D. Tilley. Tuning the selectivity of biomass oxidation over oxygen evolution on NiO–OH electrodes. Green Chemistry, 2021, 23, 8061-8068.

[3 ] DOI: 10.1039/D1SE00351H  R. Arcas, Y. Koshino, E. Mas-Marzá, R. Tsuji, H. Masutani, E. Miura-Fujiwara, Y. Haruyama, S. Nakashima, S. Ito and F. Fabregat-Santiago. Pencil graphite rods decorated with nickel and nickel–iron as low-cost oxygen evolution reaction electrodes. Sustainable Energy & Fuels, 2021, 5, 3929-3938