Eumelanin is the most common form of the pigment melanin in the human body, with diverse functions including photoprotection, antioxidant behavior, metal chelation, and free radical scavenging. Melanin also plays a role in melanoma skin cancer and Parkinson's disease. Sepia Melanin is a natural eumelanin extracted from the ink sac of cuttlefish.Eumelanin is an ideal candidate to eco-design technologies based on abundant, biosourced and biodegradable organic electronic materials, to alleviate the environmental footprint of the electronics sector.Herein, the focus is on the reversible electrical resistive switching in dry and wet Sepia eumelanin pellets, pointing to the possibility of predominant electronic transport a conditio sine qua non to develop melanin-based electronic devices. These findings shed light on

The development of technologies integrating solar energy conversion and energy storage functions is critical for limiting the anthropogenic effects on climate change and preventing possible energy shortages related to the increase of the world population. In our work, we explored the possibility to integrate the conversion and storage functions within the same multifunctional biosourced material. We identified the redox-active, quinone-based, melanin pigment, featuring a broadband absorption in the UV–vis region, as the ideal candidate for such an exploration. Electrodes of melanin on carbon paper were investigated for their morphological, optical, and voltammetric characteristics prior to being assembled into symmetric supercapacitors operating in aqueous electrolytes. We observed that, under solar light, the capacity and capacitance of melanin electrodes significantly increase with respect to the dark conditions (by 22 and 39%, respectively). Once in a supercapacitor configuration, besides featuring a Coulombic efficiency close to 100% after 5000 cycles, the capacitance and capacity of the electrodes, rated by the initial values, improve after prolonged illumination, as it is the case for the energy and power density.

In this paper, we report an easy and relatively cost effective fabrication technique of a wide band omnidirectional antireflective black silicon surface based on silicon nanowires (SiNWs).

Formic acid is considered as one of the most promising liquid organic hydrogen carriers. Its catalytic dehydrogenation process generally suffers from low activity, low reaction selectivity, low stability of the catalysts, and/or the use of noblemetal-based catalysts. Herein we report a highly selective, efficient, and noble-metal-free photocatalyst for the dehydrogenation of formic acid. This catalyst, UiO-66(COOH) 2 -Cu, is built by postmetalation of a carboxylic-functionalized Zr-MOF with copper. The visible-lightdriven photocatalytic dehydrogenation process through the release of hydrogen and carbon dioxide has been monitored in real-time via operando Fourier transform infrared spectroscopy, which revealed almost 100% selectivity with high stability (over 3 days) and a conversion yield exceeding 60% (around 5 mmol•g cat −1•h −1 ) under ambient conditions. These performance indicators make UiO-66(COOH) 2 -Cu among the top photocatalysts for formic acid dehydrogenation. Interestingly, the as-prepared UiO-66(COOH) 2 -Cu hetero-nanostructure was found to be moderately active under solar irradiation during an induction phase, whereupon it undergoes an in-situ restructuring process through intraframework cross-linking with the formation of the anhydride analogue structure UiO-66(COO) 2 -Cu and nanoclustering of highly active and stable copper sites, as evidenced by the operando studies coupled with steady-state isotopic transient kinetic experiments, transmission electron microscopy and X-ray photoelectron spectroscopy analyses, and Density Functional Theory calculations. Beyond revealing outstanding catalytic performance for UiO-66(COO) 2 -Cu, this work delivers an in-depth understanding of the photocatalytic reaction mechanism, which involves evolutive behavior of the postmetalated copper as well as the MOF framework over the reaction. These key findings pave the way toward the engineering of new and efficient catalysts for photocatalytic dehydrogenation of formic acid.

Biosourced and biodegradable organic electrode materials respond to the need for sustainable storage of renewable energy. Here, we report on electrochemical capacitors based on electrodes made up of quinones, such as Sepia melanin and catechin/tannic acid (Ctn/TA), solution-deposited on carbon paper engineered to create high-performance interfaces. Sepia melanin and Ctn/TA on TCP electrodes exhibit a capacitance as high as 1355 mF cm−2 (452 F g−1) and 898 mF cm−2 (300 F g−1), respectively. Sepia melanin and Ctn/TA symmetric electrochemical capacitors operating in aqueous electrolytes exhibit up to 100% capacitance retention and 100% coulombic efficiency over 50,000 and 10,000 cycles at 150 mA cm−2 (10 A g−1), respectively. Maximum power densities as high as 1274 mW cm−2 (46 kW kg−1) and 727 mW cm−2 (26 kW kg−1) with maximum energy densities of 0.56 mWh cm−2 (20 Wh kg−1) and 0.65 mWh cm−2 (23 Wh kg−1) are obtained for Sepia melanin and Ctn/TA.

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The integration of the solar energy conversion and electrochemical energy storage functions is critical for limiting the anthropogenic effects on climate change and preventing possible energy shortages related to the increase of the world population. Electrochemical technologies (batteries and supercapacitors) have been investigated to store the energy generated from the Sun, an intermittent source. Abundant, low-cost, non-toxic, potentially biodegradable organic molecular materials, extracted from natural sources, are ideal candidates for applications in sustainable electrochemical energy storage technologies as opposed to those currently used, often based on costly, toxic and scarce elements, thus potentially triggering geopolitical issues. Among natural materials, eumelanin, a ubiquitous biopigment in flora and fauna, stands out for its redox-activity, UV–vis absorption, chemical and thermal stability. This topical review suggests eumelanin as promising sustainable multifunctional material to enhance the electrochemical energy storage properties of organic materials by solar light. The vision behind this research is to pave a way towards the discovery of organic materials and devices that can seamlessly integrate solar energy conversion and storage within the same multifunctional material.

Operating the dry reforming reaction photocatalytically presents an opportunity to produce commodity chemicals from two greenhouse gases, carbon dioxide and methane, however, the top-performing photocatalysts presented in the academic literature invariably rely on the use of precious metals. In this work, we demonstrate enhanced photocatalytic dry reforming performance through surface basicity modulation of a Ni-CeO2 photocatalyst by selectively phosphating the surface of the CeO2 nanorod support. An optimum phosphate content is observed, which leads to little photoactivity loss and carbon deposition over a 50-hour reaction period. The enhanced activity is attributed to the Lewis basic properties of the PO43− groups which improve CO2 adsorption and facilitate the formation of small nickel metal clusters on the support surface, as well as the mechanical stability of CePO4. A hybrid photochemical-photothermal reaction mechanism is demonstrated by analyzing the wavelength-dependent photocatalytic activities. The activities, turnover numbers, quantum efficiencies, and energy efficiencies are shown to be on par with other dry-reforming photocatalysts that use noble metals, representing a step forward in understanding how to stabilize ignoble nickel-based dry reforming photocatalysts. The challenges associated with comparing the performance of photocatalysts reported in the academic literature are also commented on.