Abstract Climate change mitigation on a global scale will only be possible through the achievement of ambitious decarbonisation goals, requiring an energy transition that involves switching from fossil fuels to clean fuels such as hydrogen. The photocatalytic approach is one of the most studied methods for directly converting sunlight into hydrogen. In this work, we present the synthesis, characterization, and application of the PTZ1 ‐ HA dye, which was obtained by replacing the terminal conventional carboxylic anchoring moieties of a previously studied phenothiazine‐based dye ( PTZ1 ) with hydroxamic acid functionalities. The photoinduced performance of the two dyes as photosensitizers was compared in both dye‐sensitized solar cells and dye‐sensitized photocatalytic systems. PTZ1 ‐ HA ‐sensitized photocatalysts showed improved stability in hydrogen generation due to the introduction of the hydroxamic acid as an alternative anchor group, which was shown to slow down hydrolysis in aqueous media. Even though the light harvesting ability of PTZ1 ‐ HA was lower than that of PTZ1 , the higher stability of PTZ1 ‐ HA ‐sensitized devices allowed for improved photocatalytic generation of H 2 over prolonged periods. The superior long‐term efficiency of the hydroxamic acid based dye is important in view of potential practical applications.
Abstract Invited for the cover of this issue are the groups of S. Seki (Kyoto), G. Reginato (Sesto Fiorentino), J.‐F. Nierengarten (Strasbourg), A. Abate (Berlin) and J. L. Delgado (San Sebastian). The image depicts an artistic view of a dendrimer‐like hole transporting material at work in a perovskite solar cell. Read the full text of the article at 10.1002/chem.202101110 .
In this work, an innovative fabrication method for the realization of PEDOT:PSS-based conductive micropillars and 3D cage-like structures is presented, combining 2-photon lithography and electrodeposition techniques.
Abstract Electrochemical nitrogen reduction (E‐NRR) is one of the most promising approaches to generate green NH 3 . However, scarce ammonia yields and Faradaic efficiencies ( FE ) still limit their use on a large scale. Thus, efforts are focusing on different E‐NRR catalyst structures and formulations. Among present strategies, molecular electrocatalysts such as metal‐porphyrins emerge as an encouraging option due to their planar structures which favor the interaction involving the metal center, responsible for adsorption and activation of nitrogen. Nevertheless, the high hydrophobicity of porphyrins limits the aqueous electrolyte–catalyst interaction lowering yields. This work introduces a new class of metal‐porphyrin based catalysts, bearing hydrophilic tris(ethyleneglycol) monomethyl ether chains (metal = Cu(II) and CoII)). Experimental results show that the presence of hydrophilic chains significantly increases ammonia yields and FE , supporting the relevance of fruitful catalyst‐electrolyte interactions. This study also investigates the use of hydrophobic branched alkyl chains for comparison, resulting in similar performances with respect to the unsubstituted metal‐porphyrin, taken as a reference, further confirming that the appropriate design of electrocatalysts carrying peripheral hydrophilic substituents is able to improve device performances in the generation of green ammonia.
Dendritic-like hole transporting materials for perovskite solar cells have been prepared by functionalization of a clickable pillar[5]arene core with triarylamine dendrons. Importantly, the apparent structural complexity of the resulting compounds is not associated to a difficult synthesis which is a major advantage for applications in the field of organic electronic materials. More information can be found in the Full Paper by S. Collavini, S. Seki, J.-F. Nierengarten, A. Abate, J. L. Delgado, et al. (DOI: 10.1002/chem.202101110).
For a long time the conservation of archaeological artefacts has been based on the principles of compatibility and minimal intervention. This involves a series of partially unsolved problems, concerning the products used for deteriorated structures consolidation. The choice of materials depends on several factors such as: microclimatic conditions, application methods, and reaction time of products. Recently the employment of nanolime in the consolidation treatments of decorative carbonate matrix surfaces had a great development, thanks to multifunctional use in calcium standard‐sized particles treatments. However, while the use of the nanostructured materials is described in several specialized papers, the information about the best conditions of applicability of the nanolime and its related potentiality for the consolidation in hypogeum environment is rarely considered. The present work is devoted to represent a case study with the aim to give useful elements in order to evaluate the application of nanolime. The funerary inscriptions coming from St. Callixtus Catacombs have been the object of the research carried out in situ and in laboratory, checking indirectly in the short run and in the long run the porosity variation in the materials. The present study intends to indicate the best suspension concentration on consolidation in relationship with hypogeum environment.
Ammonia (NH3) stands as a cornerstone compound across industries, pivotal in agriculture, chemicals, and energy sectors. However, the conventional Haber-Bosch process demands high pressures, temperatures, and fossil fuels, calling for sustainable alternatives. Electrocatalytic Nitrogen Reduction Reactions (E-NRRs) and Photocatalytic Nitrogen Reduction Reactions (Photo-NRRs) present innovative routes, leveraging electricity and direct sunlight to convert nitrogen (N2) to NH3 under mild conditions, reducing emissions and softening energy requirements. Catalysts play a strategic role in these approaches, overcoming activation barriers and enhancing efficiency. However, some challenges still need to be addressed. Indeed, noble metals exhibit limits and their scarcity, geopolitical involvement, and often fluctuating costs inhibit large-scale use. Non-noble metals offer promise but require optimization and face durability concerns. Finally, carbon-based catalysts present challenges in optimization and doping. In this scenario, a molecular-based approach, comprising both specific single coordination-based molecules with transition metal centres and either metal centre coordination-based or fully organic multi-dimensional networks originating from direct molecular organic precursors, overcomes these issues while keeping the benefits of the previously mentioned classes of compounds. This mini-review explores the molecular approach to E-NRRs and Photo-NRRs from coordination compounds carrying porphyrins and phthalocyanines as organic ligands to polymeric networks based on coordination compounds between metallic centres and organic ligands (Metal-Organic Frameworks), and to networks of molecular organic units into multi-dimensional structures (Covalent Organic Frameworks). Mechanistic insights into E-NRRs and Photo-NRRs pathways elucidate N2 conversion to NH3. A critical comparative evaluation of reported catalysts has been carried out to highlight the limits and the possibilities of each class of compounds. Although challenges persist in terms of stability, cost and complexity of the synthesis, the use of a molecular approach in NRRs represents one of the most promising routes towards the sustainable preparation of ammonia.
Abstract Multi‐branched molecules have recently demonstrated interesting behaviour as charge‐transporting materials within the fields of perovskite solar cells (PSCs). For this reason, extended triarylamine dendrons have been grafted onto a pillar[5]arene core to generate dendrimer‐like compounds, which have been used as hole‐transporting materials (HTMs) for PSCs. The performances of the solar cells containing these novel compounds have been extensively investigated. Interestingly, a positive dendritic effect has been evidenced as the hole transporting properties are improved when going from the first to the second‐generation compound. The stability of the devices based on the best performing pillar[5]arene material has been also evaluated in a high‐throughput ageing setup for 500 h at high temperature. When compared to reference devices prepared from spiro‐OMeTAD, the behaviour is similar. An analysis of the economic advantages arising from the use of the pillar[5]arene‐based material revealed however that our pillar[5]arene‐based material is cheaper than the reference.
