Abdelaziz Gouda

Scaling gas-phase photocatalysis requires maximizing photon use. This study presents a PFBR with ray-tracing and simulations, validated via solar Boudouard reaction, showing higher photon efficiency than fixed beds.

The valorization of municipal solid waste permits to obtain sustainable functional materials. As the urban population burgeons, so does the volume of discarded waste, presenting both a challenge and an opportunity. Harnessing the materials and the latent energy within this solid waste not only addresses the issue of disposal but also contributes to the innovation of functional materials with applications in the energy, electronics, and environment sectors. In this perspective, technologies for converting, after sorting, municipal solid waste into valuable metals, chemicals, and fuels are critically analyzed. Innovative approaches to convert organic waste into functional carbon materials and to create, from plastic and electronic wastes, metal–organic frameworks for energy conversion, storage, and CO₂ adsorption and conversion are proposed. Green hydrometallurgy routes that permit the recovery of precious metals avoiding noble metals’ oxidative leaching, thus avoiding their downcycling, are also highlighted. The reclaimed precious metals hold promise for use in optoelectronic devices.

As the global quest for sustainable energy keeps rising, exploring novel efficient and practical photocatalysts remains a research and industrial urge. Particularly, metal organic frameworks were proven to contribute to various stages of the carbon cycle, from CO₂ capture to its conversion. Herein, we report the photo-methanation activity of three isostructural, nickel-based metal organic frameworks incorporating additional niobium, iron, and aluminum sites, having demonstrated exceptional CO₂ capture abilities from thin air in previous reports. The niobium version exhibits the highest performance, with a CO₂ to CH₄ conversion rate in the order of 750–7500 µmol*g_catalyst⁻¹*h⁻¹ between 180 °C and 240 °C, achieving 97% selectivity under light irradiation and atmospheric pressure. The in-depth characterization of this framework before and after catalysis reveals the occurrence of an in-situ restructuring process, whereas active surface species are formed under photocatalytic conditions, thus providing comprehensive structure-performance correlations for the development of efficient CO₂ conversion photocatalysts.

The rising global demand for energy requires, among others, sustainable energy storage devices. Biosourced redox‐active molecules are interesting for eco‐designed electrochemical energy storage as they increase the energy density of the electrodes adding the Faradaic (redox) storage mechanism to the electrostatic one. The engineering of the electrode surface and electrode surface/molecule interface is key to optimizing storage. Here, (i) electrodes prepared by ultrasound‐assisted modification of carbon cloth in the presence of Sepia melanin, a quinone macromolecule, and multiwalled carbon nanotubes (MWCNTs) and (ii) their use in flexible symmetric electrochemical capacitors assembled with polyvinyl alcohol (PVA)‐based hydrogel electrolyte is reported. Electrodes exhibit an areal capacitance as high as 274 mF cm⁻². Corresponding semi‐solid‐state symmetric supercapacitors feature high energy density of 18 Wh kg⁻¹, power density up to 221 W kg⁻¹ (evaluated at 0.5 A g⁻¹), outstanding cycling stability (100% capacitance retention, and 100% Coulombic efficiency after 10 000 cycles) along with excellent flexibility. This work contributes to the development of sustainable surface engineering approaches for environmentally benign electrochemical energy storage devices.

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.

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.

Organic electrode materials operating in aqueous electrolytes offer the opportunity to avoid toxic, critical, and expensive materials for electrochemical energy storage. When deposited on carbon current collectors, redox active organic materials add faradaic to electrostatic capacitance contribution to the electrodes. Here, a 3D network electrode material is reported upon, based on sepia melanin, a quinone macromolecule, and nitrogen‐ and sulfur‐doped graphitic carbon quantum dots (N,S GCQDs) designed to achieve good electronic conductivity and electrolyte wettability. The effect of various undoped and doped carbon quantum dots is also investigated, synthesized from acetic acid and sucrose instead of graphite, on the electrochemical performance of sepia melanin. Sepia/N,S GCQD shows optimum areal capacitance (≈180 mF cm⁻²) that is about twice as high as sepia (≈77 mF cm⁻²) with lower charge transfer resistance (1 ohm for sepia/N,S GCQDs compared to 10 ohms for sepia). The sepia/N,S GCQD symmetric supercapacitor in 0.5 m Na₂SO_4(aq) exhibits promising capacitance retention ≈92% after 10 000 cycles at 5 A g⁻¹, 100% coulombic efficiency, 11 µW h cm⁻² and 102 mW cm⁻² maximum energy and power densities. The work paves the way for stable and potentially biodegradable supercapacitor electrode materials for environmentally benign electrochemical energy storage.

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.

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). An effective and economical one step silver electroless catalytic etching method in an aqueous solution of AgNO₃ and HF is used for the synthesis of the black silicon surface. The formation mechanism for SiNW arrays is explained in terms of a localized nanoelectrochemical cell. The length and diameter of the nanowires were controllable as we found a commensurate relationship between dimensions and the etching time. Different sample sizes were used to prove the technique's large scale production potential. Wide range near zero reflection is reported in the visible region due to the strong trapping and antireflective properties in addition to a wide angle up to ±60°. Raman scattering measurements confirmed the quantum size effect and phonon scattering in the fabricated structure with different diameters. A black silicon surface based on solid and porous SiNWs shows promising potential for photovoltaic, optoelectronic and energy storage applications.