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The Sun generates enough energy to power the Earth. However, solar energy should be stored into chemical energy to be conveniently used due to its low energy density and discontinuous radiation. In the last several years, photocatalysis and photoelectrochemistry for solar fuels have reattracted more and more governments' and people's interest from all over the world and become a very hot topic. If we utilize the abundant solar energy to convert CO2 into hydrocarbon fuels especially, it would address the problems of global climate change and solar energy storage at the same time. Recently, different new materials and ideas have been proposed and steady scientific progress has been done. However, it is still a key challenge to explore visible-light responsive materials with high photocatalytic activities. The special issue contains eight papers, where 6 papers are related to visible-light activity and 2 papers are related to UV activity.

To achieve climate protection goals set out by national governments and the United Nations, it is paramount to reduce society's dependence on fossil fuels and to introduce more sustainable energy solutions. Furthermore, to not only protect our climate but the natural environment in general, it is necessary to reduce humanity's waste production and to turn waste into a resource wherever possible. The solutions to both of these ambitions will heavily rely on new chemical processes being discovered and upscaled. Thus, with catalysis and photochemistry at its heart, the challenge to build a greener and more sustainable future is largely a materials discovery and design problem. In this work, I introduce a new way of aligning the electronic energy levels of semiconductors with respect to redox potentials which might facilitate in silico screening studies of materials suitable for photoelectrochemistry. In particular, I demonstrate how continuum solvation models can be used to replace computationally expensive atomistic descriptions of water when describing an electrode-electrolyte interface. I tested this approach on rutile (TiO2) showing that, when combined with a description of rutile's electronic structure within many-body perturbation theory, the proposed alignment procedure yields the correct positioning of rutile's band edges on the standard hydrogen electrode scale. My investigation surfaced and explained important differences between atomistic and continuum solvation models when describing the electric potential across interfaces. Furthermore, I present a detailed study of the electronic structure of osmium dioxide (OsO2) near its Fermi level. OsO2 is closely related to important catalysts such as IrO2 and RuO2, which also crystallise in the rutile structure. Specifically, by collaborating with colleagues specialised in experimental photoelectron spectroscopy (PES), we highlight the importance of computational insights for the correct interpretation of PES spectra. By going beyond a simple comparison between the experimentally measured PES spectrum and the computed single-particle electronic density of states, we reveal that the spectrum of OsO2 features a rare low-energy bulk plasmon satellite. ; Open Access

Work presented at the NanoteC19 conference, International Conference on Carbon Nanosciene and Nanotechnology, 27th-30th august 2019, Zaragoza (Spain). ; Photoelectrochemistry of nanomaterials is commonly employed in fields related to energy and environmental applications, such as water splitting, solar cells or water remediation. It is a valuable technique for the direct evaluation of the performance for the desired application. In addition, it can be used for the study of intrinsic electronic properties of nanostructured of a great variety of semiconductor materials, such as conductive polymers or metal oxide nanoparticles. It is also a highly valuable implement to assess charge and/or energy transfer phenomena between the mentioned semiconductors and carbon nanomaterials (GO, CNTs), unveiling their role as charge acceptors/donors, blockers/transporters, sensitizers/conditioners, or even as electroactive materials for themselves, thus allowing the tuning of optoelectronic properties of composite materials. This versatility makes photoelectrochemistry a key tool in the field of carbon nanoscience and nanotechnology [1- 4]. ; MINECO (project ENE2016-79282-C5-1-R), European Union (H2020-MSCA-ITN-2014-ETN 642742), Gobierno de Aragón (Grupo Reconocido DGA T03_17R), and associated EU Regional Development Funds.

1 figure.-- Talk delivered at the HeteroNanoCarb-2019 Conference, Advances and applications in carbon related nanomaterials: From pure to doped structures including heteroatom layers, 2019, December 09th -- 13th, Centro de Ciencias de Benasque Pedro Pascual in Benasque (Aragon, Spain). ; Photoelectrochemistry is a valuable technique for the study of intrinsic electronic properties of a great variety of nanostructured semiconductor materials, such as conductive polymers or metal oxide nanoparticles. It is also a highly valuable implement to assess charge and/or energy transfer phenomena between the mentioned semiconductors and carbon nanomaterials (GO, CNTs), unveiling their role as charge acceptors/donors, blockers/transporters, sensitizers/conditioners, or even as photoelectroactive materials for themselves, thus allowing the tuning of optoelectronic properties of composite materials, for their future application in fields related to energy and environment, such as water splitting, solar cells or water remediation. This versatility makes photoelectrochemistry a key tool in the field of carbon nanoscience and nanotechnology. ; MINEICO (project ENE2016-79282-C5-1-R, AEI/FEDER, UE), European Union (H2020-MSCA-ITN-2014-ETN 642742 ), Gobierno de Aragón (Grupo Reconocido DGA T03_17R, FEDER, UE).

1 Figure.-- Abstract of the work presented at "Current Trends in Electrochemistry", 41st Meeting of the Electrochemisty Group of the Spanish Royal Society of Chemistry, 1st French‐Spanish Atelier/Workshop on Electrochemistry, 6 - 9 July 2021, Paris (France). ; Photoelectrochemical techniques are accurate for the study of intrinsic electronic properties of a great variety of nanostructured semiconductor materials, such as conductive polymers, carbon nanomaterials (GO, CNTs, CDs) or metal oxide nanoparticles. It is also a highly valuable implement to assess charge and/or energy transfer phenomena between the mentioned semiconductors unveiling their role as charge acceptors/donors, blockers/transporters, sensitizers/conditioners, or even as photoelectroactive materials for themselves, thus allowing the tuning of optoelectronic properties of composite materials, for their future application in fields related to energy and environment, such as water splitting, electronics, solar cells or water remediation. This versatility makes photoelectrochemistry a key tool in the field of nanoscience and nanotechnology. ; MINECO and AEI/FEDER/UE (project ENE2016-79282-C5-1-R), European Union (H2020-MSCAITN- 2014-ETN 642742), Gobierno de Aragón (Grupo Reconocido DGA T03_17R, FEDER/UE). ; Peer reviewed

[EN] NADH is a key biomolecule involved in many biocatalytic processes as cofactor and its quantification can be correlated to specific enzymatic activity. Many effort s have been t aken to obt ain clean electrochemical signals related to NADH presence and lower its redox overpotential to avoid interferences. Suppression of background and secondary signals can be achieved by including a switchable electroactive surface, for instance, by using semiconductors able to harvest light energy and drive the excited electrons only when irradiated. Here we present the combination of a n-type Si semiconductor with fibers made of carbon nanotubes as electroactive surface for NADH quantification at low potentials only upon irradiation. The resulting photoelectrode responded linearly to NADH concentrations from 50 μM to 1.6 mM with high sensitivity (54 μA cm −2 mM −1 ). This system may serve as a biosensing platform for detection and quantification of dehydrogenases' activity. ; European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 713366 . A.D.L., M.R and J.J.V. thank the "Comunidad de Madrid "for its support to the FotoArt-CM project ( S2018/NMT-4367 ) through the Program of R&D activities between research groups in Technologies 2018, co- financed by European Structural Funds. J.J.V. is grateful for generous financial support provided by the European Union Horizon 2020 Program under grant agreement 678565 (ERC-STEM) and by the MINECO ( RyC-2014-15115 HYNANOSC RTI2018-099504-A-C22 ; Peer reviewed

Introducing molecular dopants in carbon nitride has been shown to dramatically modify its electronic structure, resulting in efficient charge separation and improved photocatalytic efficiency. Herein, we have studied the effect of doping carbon nitride with 2-aminothiophene-3-carbonitrile. A fundamental photoelectrochemical characterization has been performed comparing the behavior of the resulting material (ATCN) with undoped carbon nitride (CN). On the one hand, it is shown that the photocurrent onset shifts with the pH up to a value of 8 for both materials, as expected theoretically. On the other, ATCN, which benefits from additional light absorption, shows an improved photoactivity toward hydrogen evolution. In addition, it displays intriguing photoluminescence properties that can be additionally engineered by modulating the potential. In a more general vein, this study illustrates how to shed light on the effects of introducing molecular dopants in the CN matrix. ; We are grateful to the Spanish Ministry of Education and Competitiveness for financial support through projects MAT2012-37676 and MAT2015-71727-R (co-financed with FEDER funds by the European Union). A.-K.D.G. thanks the Mexican government (CONACYT) for the award of a doctoral grant.

This compendium reports fundamental science and engineering advances of the US Army Research Labratory (ARL) within the area of Energy and Power technologies. Keywords: Biomaterials, Structural Materials, High Strain Materials, Ballistic Materials, Manufacturing Science, Electrochemical Energy Storage, Batteries, Capacitors, Electrochemical Energy Conversion, Fuel Cells, Photoelectrochemistry, Photochemistry, High Voltage Electrolytes, Li-ion Batteries, Li-ion Chemistry, Lithium-Sulphur Batteries, Nuclear Metastables, Pyroelectric Energy Conversion, Charged Quantum Dots, High-Efficiency Photov.

1 figure.-- Comunicación oral presentada en el congreso ChemOnTubes 2022, celebrado en San Sebastián, del 24 al 28 abril. ; Carbon Dots (CDs) have attracted considerable attention due to their excellent photoluminescence (PL), high photochemical stability, easy functionalization, water solubility, low toxicity and good biocompatibility, among others. All these properties elevate CDs as a potential alternative to conventional quantum dots, thus overcoming issues of toxicity due to the presence of heavy metals [1]. The outstanding properties of CDs have enabled their application in many research fields, such as biomedicine [2], photocatalysis, photovoltaics, photoelectrochemistry [3], and sensing. Actually, most of the reported CDs show intrinsic blue emission, whose PL mechanism has been studied in depth [4]. However, there is increased research activity to obtain CDs with longer emission wavelengths. Herein, we present the bottom-up microwave synthesis, optimization and characterization of water-soluble CDs with high PL quantum yield and green emission. Moreover, the intense PL is maintained even in the solid state, when embedded in a biopolymer matrix. Finally, we demonstrate that the CDs show great promise as sensitizers in TiO2 photoanodes, integrated into a photoelectrochemical cell for the production of green hydrogen. ; Spanish MICINN/AEI: PID2019-104272RB-C51/AEI/10.13039/501100011033; Government of Aragón: Grupos Reconocidos DGA T03_20R and PhD grant of MAA IIU/796/2019. ; Peer reviewed

Low-cost large-diameter cubic silicon carbide (3C-SiC) film grown on silicon (Si) has been demonstrated to have a wide range of applications in photonics, electronics, photoelectrochemistry and micro-electro-mechanical system technologies. In this paper, the epitaxial growth of SiC on Si by low-pressure chemical vapour deposition is investigated. Two modes were employed to supply the precursors: the alternating supply and the simultaneous supply. Compared with SiC films grown at the same temperature by simultaneous supply epitaxy method, the SiC grown by alternating supply epitaxy (ASE) method has better crystallinity, smoother surface, and better thickness uniformity as confirmed by X-ray diffraction and atomic force microscopy characterisation. We propose the growth mechanism for ASE growth of 3C-SiC and validate it in detail experimentally. It is found that, Si deposition on SiC follows either Stranski–Krastanov mode or island growth mode, while SiC formation proceeds in two possible reaction paths: redistributing of the formed Si islands or smoothing of the formed SiC islands by decomposition migration process. Both reaction paths are driven by minimizing the surface free energy and reducing dangling bonds density. In summary, the key features of ASE are: (1) Si has a longer diffusion length and thus higher probability to adhere to a crystallographically favourable position; (2) undesirable gas phase reactions can be avoided. The obtained results indicate that ASE is a unique and economically viable method to prepare uniform 3C-SiC on multiple large-diameter Si wafers. ; Queensland Government, Australia ; Australian Research Council