Eur. J. Inorg. Chem. 2019, © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Guest Editorial 2017 2017–2019 DOI: 10.1002/ejic.201900289 Redox Catalysis for Artificial Photosynthesis Xavier Sala* [a] and Antoni Llobet* [a,b] Nature has always inspired mankind. The way green plants, algae, and cyanobacteria have been using sunlight to produce energetically rich biomolecules (solar fuels) through photosyn- thetic processes [1] since over a billion years is no exception. Dur- ing the last decades, the progressive depletion of fossil fuels and the obvious impact of their continuous and massive combustion on our health and environment, particularly on global warm- ing, [2] have triggered eforts directed to their replacement. Thus, artifcial photosynthetic strategies based on the production of clean and renewable energy alternatives driven by sunlight have arisen as a core feld of research. [3,4] Artifcial photosynthesis tries to emulate Nature, generating devices for the storage of sunlight energy into chemical bonds, thus producing a solar fuel. Following Nature’s steps, water oxidation is a central process in artifcial photosynthesis, [5] constitut- ing the source of electrons, which are then used to reduce CO 2 to liquid fuels, [6] protons to dihydrogen, [7] or even N 2 to ammonia. [8] Given the complexity of the whole process, a division-of-labor ap- proach is usually implemented, and the overall process is divided into two half-reactions: water oxidation (WO) and the corresponding reductive counterpart (hydrogen evolution, HE, or CO 2 reduction, CO 2 red). Together with efcient light absorption systems, the kinetic viability of the whole process depends on the availability of fast and robust redox catalysts that can work at low overpo- tentials and speed up the corresponding oxidative/reductive processes. Redox catalysis is thus at the core of artifcial photosynthesis, with either metal/metal-oxide or molecular catalysts (both with their own pros and cons) as potential candidates for catalyzing the set of redox reactions involved. Beyond the obvious, required eforts in catalyst preparation and mechanistic analysis aiming at the rational design of im- proved catalysts, the engineering of (photo)anodes and (photo) cathodes combining light-harvesting molecules/materials and catalytic species is also a major challenge, as is the fnal integra- tion of the two half-reactions in photoelectrochemical cells (PEC) for the overall production of solar fuels. The harmonic function of the diferent integrating components and their long-term stabil- [a] Departament de Química, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, 08193 Barcelona, Spain E-mail: xavier.sala@uab.cat https://seloxcat.wordpress.com/ [b] Institute of Chemical Research of Catalonia (ICIQ), Barcelona Institute of Science and Technology (BIST), Avinguda Països Catalans 16, 43007 Tarragona, Spain E-mail: allobet@iciq.cat http://www.iciq.org/research/research_group/prof-antoni-llobet/ ORCID(s) from the author(s) for this article is/are available on the WWW under https://doi.org/10.1002/ejic.201900289. Xavier Sala started his research in redox catalysis with a PhD thesis from the University of Girona on the application of Ru-based molecular complexes in selec- tive oxidation processes. In 2006 he moved to the Institute of Chemical Research of Catalonia (ICIQ, Tarragona) for post-doc- toral research in organometallic chemis- try under the supervision of Prof. P. W. N. M. van Leeuwen and was appointed scientifc group coordinator in Prof. Antoni Llobet’s group at ICIQ in 2008, focusing on the feld of artifcial photo- synthesis. After a third post-doctoral stay at the Institute of Agrifood Research and Technology (IRTA), he was appointed as Lecturer in Chemistry at the Autonomous University of Barcelona in 2010, where he became Associate Professor in 2018. Since 2011, he leads the Selective Oxidation Catalysis (SelOxCat) research group focused on the key reactions involved in the production of renewable fuels through redox catalysis, with particular emphasis on tailored metal and metal-oxide nano- materials. He has co-authored over 70 research papers (includ- ing 5 book chapters) and has been visiting professor at the University of California Berkeley (Berkeley, USA) and Invited Professor at the LCC-CNRS (Toulouse, France). Anoni Llobet was born in Sabadell (Bar- celona) in 1960. After his PhD at the Uni- versitat Autònoma de Barcelona (UAB) with Prof. Francesc Teixidor in July 1985, he moved to the University of North Carolina at Chapel Hill for a postdoctoral stay with Prof. Thomas J. Meyer, until the end of 1987. After a short period again at UAB and at the University of Sussex-Dow Corning (UK), he became Scientifc Ofcer for the Commission of the European Commu- nities, based in Brussels, Belgium (1990–1991). From 1992 to 1993, he was Senior Research Associate at Texas A&M University in College Station (USA), working with the groups of Prof. Arthur E. Martell and Donald T. Sawyer. From 1993 to 2004, he was part of the faculty of the Universitat de Girona, where he was promoted to Full Professor in 2000. At the end of 2004 he moved to UAB. In September 2006, he was appointed as Group Leader at the Institute of Chemical Research of Catalonia (ICIQ) in Tarragona. His research interests include the development of tailored transition metal complexes as catalysts for selective organic and inorganic transformations including the oxidation of water to molecular dioxygen, supramolecular catalysis, the activation of C–H and C–F bonds, and the preparation low-molecular-weight complexes as structural and/or functional models of the active sites of oxidative metalloproteins.