Hydrogen production is frequently driven by renewable and non-renewable energy resources, such as fossil fuels, especially steam reforming of methane, the nafta reform, from biomass and from biological sources [1]. Unfortunately, these hydrogen production methods can be expensive, partially efficient, and environmentally polluting, as well as these also produce hydrogen with low-purity. Meanwhile, the unique way to produce the cleanest hydrogen is from the well-known process of water electrolysis or commonly named, water splitting. However, the high energy expenditure is its main disadvantage. Electrolytic water splitting devices are an attractive technology for producing clean hydrogen gas which consist of stacks of electrochemical cells in which the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) take place at cathode and anode compartments, respectively [1]. Water electrolyzers are an established commercial technology, however, the use of other water matrices as resources for producing clean hydrogen remains limited.

Another way to offset the cost and safety problems for producing hydrogen from electrolysis would be a hybrid approach. On the contrary to use clean water sources for anodic process, OER is replaced by an electrochemical organic oxidation reaction with aqueous effluents or by producing oxidants. The most popular electrolytic process for removing organic pollutants from different water matrices is electrochemical oxidation (EO) [2,3] as well as to produce oxidizing species, which is highly efficient and versatile, safe and is considered an environmentally-friendly technology when coupled to renewable energies [4].

Nowadays, hybrid electrolysis strategies are particularly attractive in the context of a circular economy as these can be coupled with the use of more complex water matrices to transform organics depollution into an energy resource for the production of hydrogen as a chemical energy carrier. It is important to remark that, the use of organic compounds as sacrificial analytes could be a good alternative for splitting water to produce H₂ because it reduces the amount of energy spent in the electrolysis process.

The benefits of hybrid electrolysis are multifaceted to valorize low-value organics or waste, reaching significant technical impacts in the form of versatile, safety of operation, efficient, and cost-effective technology; as well as integrating electrochemical-based solutions to fulfill Sustainable Development Goals (SDG 6 and 7) (i.e., depollution of water, sanitation, disinfection, water sustainability and energy security by green and modern energy sources) [5]. Afterwards, replacing the OER with the EO, the use of specific electric power conditions could constitute an increase in the effectiveness of both process and a decrease on the component costs associated with membranes and electrocatalysts/electrode materials as well as electrolyzers. On the one hand, the key emerging technology in energy-water innovation solutions, due to the intensification of energy demands as well as water sustainability in world; is combining renewable energy sources with energy-efficient water treatment methods. Therefore, the objective of this work is to demonstrate that hydrogen is efficiently produced simultaneously with the EO of organic compounds or oxidants such as persulfate, using as a sacrificial analyte with a split electrochemical flow cell, featuring a BDD electrode as anode and a 316-type stainless-steel as cathode. The technology proposed here uses a photovoltaic array as an energy source to drive the operation of the designed PEM-type cell, establishing a promising, efficient, and sustainable alternative to produce green hydrogen.

[1] J.E.L. Santos, D.R. Da Silva, C.A. Martínez-Huitle, E.V. Dos Santos, M.A. Quiroz, Cathodic hydrogen production by simultaneous oxidation of methyl red and 2,4-dichlorophenoxyacetate in aqueous solutions using PbO2, Sb-doped SnO2and Si/BDD anodes. Part 2: Hydrogen production, RSC Adv. 10 (2020) 37947–37955. https://doi.org/10.1039/d0ra03954c.

[2] I. Sirés, E. Brillas, Remediation of water pollution caused by pharmaceutical residues based on electrochemical separation and degradation technologies: A review, Environ. Int. 40 (2012) 212–229. https://doi.org/10.1016/j.envint.2011.07.012.

[3] E. Brillas, C.A. Martínez-Huitle, Decontamination of wastewaters containing synthetic organic dyes by electrochemical methods. An updated review, Appl. Catal. B Environ. 166–167 (2015) 603–643. https://doi.org/10.1016/j.apcatb.2014.11.016.

[4] S.O. Ganiyu, E. Vieira dos Santos, E.C. Tossi de Araújo Costa, C.A. Martínez-Huitle, Electrochemical advanced oxidation processes (EAOPs) as alternative treatment techniques for carwash wastewater reclamation, Chemosphere. 211 (2018) 998–1006. https://doi.org/10.1016/j.chemosphere.2018.08.044.

[5] B.K. Mishra, S. Chakraborty, P. Kumar, C. Saraswat, Sustainable Solutions for Urban Water Security, 93 (2020). https://doi.org/10.1007/978-3-030-53110-2.