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Renewable fuel generation is essential for a low carbon footprint economy. Thus, over the last five decades, a significant effort has been dedicated towards increasing the performance of solar fuels generating devices. Specifically, the solar to hydrogen efficiency of photoelectrochemical cells has progressed steadily towards its fundamental limit, and the faradaic efficiency towards valuable products in CO2 reduction systems has increased dramatically. However, there are still numerous scientific and engineering challenges that must be overcame in order to turn solar fuels into a viable technology. At the electrode and device level, the conversion efficiency, stability and products selectivity must be increased significantly. Meanwhile, these performance metrics must be maintained when scaling up devices and systems while maintaining an acceptable cost and carbon footprint. This roadmap surveys different aspects of this endeavor: system benchmarking, device scaling, various approaches for photoelectrodes design, materials discovery, and catalysis. Each of the sections in the roadmap focuses on a single topic, discussing the state of the art, the key challenges and advancements required to meet them. The roadmap can be used as a guide for researchers and funding agencies highlighting the most pressing needs of the field.

153, 174303 (2020).10.1063/5.0023754 13 M. Peralta, S. Feijoo, S. Varela, V. Mujica, and E. Medina, "Coherence preservation and electron-phonon interaction in electron transfer in DNA", J. Chem. Phys. A. The reorganization energy - Electron phonon coupling In addition to the free energy change, the Marcus rate expression requires two additional parameters, the electronic coupling and the reorganization energy, often denoted as I i . Electron transfer (ET), as a simplest chemical reaction, is the fundamental step in the oxidation-reduction reaction, involved in a large class of electrochemistry, biochemistry, and organic and inorganic chemistry. 63, 4358-4368 (1975).10.1063/1.431152 12 M. K. Nuraliev, O. D. Parashchuk, N. V. Tukachev, Y. A. Repeev, D. R. Maslennikov, O. V. Borshchev, Y. G. Vainer, D. Y. Paraschuk, and A. Y. Sosorev, "Toward probing of the local electron-phonon interaction in small-molecule organic semiconductors with Raman spectroscopy", J. Chem. Phys. [Extracted from the article]

Direct excitation of aromatic compounds grants access to high‐energy intermediates that can be utilised in organic synthesis. Understanding and predicting the substituent effects at the excited state for aromatic molecules remains challenging for the synthetic photochemist. In this work, we present an experimental and computational investigation of the excited state of the isomeric chloroanilines, which promptly react by losing the chloride when the amino group is in para position, but are non‐reactive and non‐emissive in the meta and ortho isomers. XMS‐CASPT2//CASSCF computations explain this apparent contradiction of the meta‐ortho selectivity rule of Zimmerman, which originates from the substituent effects lowering to a different extent the barrier to populate the prefulvenic conical intersection that deactivates non‐radiatively the singlet excited state of the chloroanilines. [ABSTRACT FROM AUTHOR]

To gain a deeper understanding of the underlying charge processes in dye sensitized photocathodes, lateral electron hopping across dye-sensitized NiO photocathodes was investigated. For dye-sensitized systems, hole hopping across photoanodes has been studied extensively in the literature but no expansive studies on electron hopping in sensitized photocathodes exist today. Therefore, an organic p-type dye (TIP) with donor–linker–acceptor design, showing high stability and electrochemical reversibility, was used to study the electron transfer dynamics (electron-hopping) between dyes with temperature dependent spectroelectrochemistry and computational simulations. Besides intermolecular electron-hopping across the surface with a rate constant in the order of 105 s−1, our results show a second electron hopping pathway between NiO surface states with a rate constant in the order of 107 s−1, which precedes the electron hopping between the dyes. Upon application of a potential step negative enough to reduce both the dye and NiO surface states, the majority of NiO surface states need to be reduced before intermolecular electron transfer can take place. The results indicate that, in contrast to sensitized photoanodes where intermolecular charge transfer is known to influence recombination kinetics, intermolecular charge transport processes in TIP dye sensitized NiO photocathodes is less relevant because the fast electron transport between NiO surface states likely dominates recombination kinetics. [ABSTRACT FROM AUTHOR]