Conversion Of Chemical Energy Research Articles

Rapid detection of donor-dependent photocatalytic hydrogen evolution by NMR spectroscopy.

Understanding molecular processes at nanoparticle surfaces is essential for designing active photocatalytic materials. Here, we utilize nuclear magnetic resonance (NMR) spectroscopy to track photocatalytic hydrogen evolution using donor molecules and water isotopologues. Pt–TiO2 catalysts were prepared and used for isotopic hydrogen evolution reactions using alcohols as electron donors. 1H NMR monitoring revealed that evolution of the H2 and HD species is accompanied by the oxidation of donor molecules. The isotopic selectivity in the hydrogen evolution reaction gives rise to formal overpotential. Based on a comparison of the rates of hydrogen evolution and donor oxidation, we propose the use of ethanol as an efficient electron donor for the hydrogen evolution reaction without re-oxidation of radical intermediates.

Multi Compression-Expansion Process for Chemical Energy Conversion: Transformation of Methane to Unsaturated Hydrocarbons and Hydrogen

Multi Compression-Expansion Process for Chemical Energy Conversion: Transformation of Methane to Unsaturated Hydrocarbons and Hydrogen

Energetic Study on Jordanian Olive Cake and Woody Biomass Materials

In this work, the potential for energy production in Jordan was explored using four distinct types of biomass samples (olive cakes, woods). The proximate analysis, oil content, and higher heating value were all determined experimentally and compared to other biomass previously published in the literature. The findings appear to be similar to other biomass materials utilized as solid biofuel feed-stock materials. Olive cake and wood samples have lower calorific values than anthracite coal, ranging from 25% to 40% lower. According to the results of this study, olive cake samples had the highest oil extractive content (14.5 wt%), followed by pine and beech woody samples with 8.9 wt% and 3.1 wt%, respectively. The calorific values of the biomass samples tested ranged from 18 to 22 MJ/kg, making them suitable for use as fuel. Moreover, the high volatile matter content (78% to 93%) was appropriate for chemical energy conversion by gasification or combustion process. Jordan can create roughly 8000 tons of pomace oil per year from the waste solid olive cake, based on existing results. Furthermore, the olive cake’s energy potential in Jordan is estimated to be 38 MW based on the higher heating value of the tested samples and the annual quantity of this resource. In the meantime, due to limited annual production, Jordanian firewood has the modest energy potential (2.4 MW).

Nanocatalytic Materials for Energy-Related Small-Molecules Conversions: Active Site Design, Identification and Structure-Performance Relationship Discovery.

The catalytic conversion of energy-related small-molecules is a critical process in the fields of chemical production, environmental restoration, and energy conversion and storage. Over the years, numerous nanocatalytic materials have been explored in efforts to substantially boost the inherently sluggish catalytic processes. Despite achievements, the lack of fundamental insights into the design and identification of active sites and the structure-performance relationship has been one of the main obstacles to further improvement in catalytic performance. With the development of first-principles density functional theory (DFT) calculations and state-of-art spectroscopic techniques, the pace of research has started to move forward again.In this Account, we illustrate our recent representative attempts to gain fundamental insights into the rational development of efficient nanocatalytic materials and thus boost the typical electrochemical and mechanochemical conversions of energy-related small-molecules, including for the hydrogen evolution reaction (HER), oxygen reduction reaction (ORR), and ammonia synthesis. DFT calculations and advanced spectroscopic techniques, such as synchrotron radiation-based X-ray absorption spectroscopy (XAS, hard and soft X-ray), were properly adopted for this purpose.Specifically, to achieve a fast-electrochemical hydrogen evolution process, Ir active sites with balanced hydrogen adsorption/desorption behaviors were first computationally designed via orbital modulation and experimentally identified, and they showed significantly enhanced catalytic activity toward HER in acidic media. For the electrochemical reduction of oxygen, well-designed Zn-N2 active sites and quinone functional groups were introduced into the different carbon matrixes and structurally identified by the XAS technique, utilizing hard and soft X-rays, respectively. Both experimental and DFT studies revealed that Zn-N2 active sites with their unique structure can greatly activate the adsorbed oxygen species, leading to a highly efficient and selective four-electron oxygen reduction pathway, while the quinone functional groups are able to modify the activation mode and alter it into a selective two-electron oxygen reduction pathway for H2O2 production.In another study, inspired by the dissociation of stable nitrogen molecules on the surface of Fe, dynamic strained Fe active sites were designed for mechanochemical ammonia synthesis. Combined XAS and Mössbauer spectroscopy revealed the formation of a short-range Fe4N structure by the Fe active sites and dissociated nitrogen during the ball milling process, facilitating robust hydrogenation and ammonia production under mild conditions.Thanks to the theoretical methods and advanced spectroscopic techniques, fundamental insights into the design and identification of active sites and understanding of the structure-performance relationship can be easily obtained using such tools, which will guide the development of nanocatalytic materials and boost the conversions of energy-related small-molecules for various applications.

Metallic Copper-Containing Composite Photocatalysts: Fundamental, Materials Design, and Photoredox Applications.

Semiconductor photocatalysis has long been regarded as a potential solution to tackle the energy and environmental challenges since the first discovery of water splitting by TiO2 almost 50 years ago. The past few years have seen a tremendous flurry of research interest in the modification of semiconductors because of their shortcomings in the aspects of solar harvesting, electron-hole pairs separation, and utilization of photogenerated carriers. Among the various strategies, the introduction of metallic copper into the photocatalysis system can not only enhance the absorption of sunlight and the separation efficiency of photogenerated electrons and holes, but also increase the adsorption ability of substrate and the number of active sites, so as to realize the high solar to chemical energy conversion efficiency. This review focuses on the rational design of copper-based composites and their applications in photoredox catalysis. First, the preparation methods of metallic copper-containing composites are discussed. Then, the applications of different types of copper-based composites in the photocatalytic removal of pollutants, splitting of water to hydrogen production, reduction of carbon dioxide, and conversion of organic matter are introduced. Finally, the opportunities and challenges in the design and synthesis of copper-based composites and their applications in the photocatalysis are prospected.

Sustainable strategy on microbial fuel cell to treat the wastewater for the production of green energy

Microbial fuel cell (MFC) is one of the promising alternative energy systems where the catalytic conversion of chemical energy into electrical energy takes places with the help of microorganisms. The basic configuration of MFC consists of three major components such as electrodes (anode and cathode), catalyst (microorganism) and proton transport/exchange membrane (PEM). MFC classified into four types based on the substrate utilized for the catalytic energy conversion process such as Liquid-phase MFC, Solid-phase MFC, Plant-MFC and Algae-MFC. The core performance of MFC is organic substrate oxidation and electron transfer. Microorganisms and electrodes are the key factors that decide the efficiency of MFC system for electricity generation. Microorganism catalysis degradation of organic matters and assist the electron transfer to anode surface, the conductivity of anode material decides the rate of electron transport to cathode through external circuit where electrons are reduced with hydrogen and form water with oxygen. Not limited to electricity generation, MFC also has diverse applications in different sectors including wastewater treatment, biofuel (biohydrogen) production and used as biosensor for detection of biological oxygen demand (BOD) of wastewater and different contaminants concentration in water. This review explains different types of MFC systems and their core performance towards energy conversion and waste management. Also provides an insight on different factors that significantly affect the MFC performance and different aspects of application of MFC systems in various sectors. The challenges of MFC system design, operations and implementation in pilot scale level and the direction for future research are also described in the present review.

Nanostructure Engineering via Intramolecular Construction of Carbon Nitride as Efficient Photocatalyst for CO2 Reduction.

Light-driven heterogeneous photocatalysis has gained great significance for generating solar fuel; the challenging charge separation process and sluggish surface catalytic reactions significantly restrict the progress of solar energy conversion using a semiconductor photocatalyst. Herein, we propose a novel and feasible strategy to incorporate dihydroxy benzene (DHB) as a conjugated monomer within the framework of urea containing CN (CNU-DHBx) to tune the electronic conductivity and charge separation due to the aromaticity of the benzene ring, which acts as an electron-donating species. Systematic characterizations such as SPV, PL, XPS, DRS, and TRPL demonstrated that the incorporation of the DHB monomer greatly enhanced the photocatalytic CO2 reduction of CN due to the enhanced charge separation and modulation of the ionic mobility. The significantly enhanced photocatalytic activity of CNU–DHB15.0 in comparison with parental CN was 85 µmol/h for CO and 19.92 µmol/h of the H2 source. It can be attributed to the electron–hole pair separation and enhance the optical adsorption due to the presence of DHB. Furthermore, this remarkable modification affected the chemical composition, bandgap, and surface area, encouraging the controlled detachment of light-produced photons and making it the ideal choice for CO2 photoreduction. Our research findings potentially offer a solution for tuning complex charge separation and catalytic reactions in photocatalysis that could practically lead to the generation of artificial photocatalysts for efficient solar energy into chemical energy conversion.

Sustainable synthesis of a new semiamorphous Ti-BDC MOF material and the photocatalytic performance of its ternary composites with Ag3PO4 and g-C3N4

Ti-MOFs have significant research and industrial demand due to their extraordinary photocatalytic potential. However, the number of known Ti-MOFs is quite limited compared to other high-valent based MOFs. In this work, we present a new Ti-MOF, prepared under environmental, energetic and economical (3E) sustainable conditions and which is potentially scalable, as it is quickly prepared at room temperature, which makes it competitive with the widely used conventional MIL-125(Ti). Moreover, novel Ti-BDC based ternary photocatalysts were successfully prepared by mixing Ti-BDC with g-C3N4 and Ag3PO4. These composites reduce the shortcoming associated with visible light absorption, recombination, and the transfer of photogenerated charges of Ti-BDC. They possess high surface interaction between the three components, high solar to chemical energy conversion and excellent photocatalytic performance in the degradation of methyl orange (94% in 90 min and 99% in 60 min when exposed to indoor or outdoor systems, respectively) due to multi-structural and synergistic effects. Importantly, the catalytic efficiency did not decrease significantly even after the fourth reaction cycles, showing its good stability and recyclability. Moreover, the presence of Ag0 will knock a new insight in the photo-excited charge carrier transfer from conventional to Z-scheme mechanisms.

The Selective Transport of Ions in Charged Nanopore with Combined Multi-Physics Fields.

The selective transport of ions in nanopores attracts broad interest due to their potential applications in chemical separation, ion filtration, seawater desalination, and energy conversion. The ion selectivity based on the ion dehydration and steric hindrance is still limited by the very similar diameter between different hydrated ions. The selectivity can only separate specific ion species, lacking a general separation effect. Herein, we report the highly ionic selective transport in charged nanopore through the combination of hydraulic pressure and electric field. Based on the coupled Poisson–Nernst–Planck (PNP) and Navier–Stokes (NS) equations, the calculation results suggest that the coupling of hydraulic pressure and electric field can significantly enhance the ion selectivity compared to the results under the single driven force of hydraulic pressure or electric field. Different from the material-property-based ion selective transport, this method endows the general separation effect between different kinds of ions. Through the appropriate combination of hydraulic pressure and electric field, an extremely high selectivity ratio can be achieved. Further in-depth analysis reveals the influence of nanopore diameter, surface charge density and ionic strength on the selectivity ratio. These findings provide a potential route for high-performance ionic selective transport and separation in nanofluidic systems.

Detonation of a nitromethane-based energetic mixture driven by electrical wire explosion

The combination of energetic material (EM) and an electrical wire explosion (EWE) is an important way to achieve effective release and conversion of electrical and chemical energy, e.g. by generating strong underwater shock waves (SWs) that can be used for dynamic reservoir fracturing in unconventional gas exploitation. This letter proposes a mud-like EM composed of nitromethane, aluminium and copper oxide powder, which can be detonated directly by a tungsten wire explosion. The detonation and successive deflagration result in notably enhanced SWs: with 2.8 g EM, the SW amplitude, impulse and energy are respectively increased by 1.7, 2.1, and 7.9 times compared to an optimal underwater EWE. A direct thermal initiation mechanism for the detonation process is proposed, with the exploding wire, the Joule heating along the current path in the EM and the Al/CuO thermite reaction all serving as heat sources. It is found that the Joule heating and chemical reactions reinforce each other, which is likely the key to the ‘easy’ detonation of nitromethane.

Solar-Driven Gas-Phase Moisture to Hydrogen with Zero Bias.

Band structure engineering offers a perfect route to tune the transport properties of electrons and holes independently, especially in semiconductors for water splitting. Here, we explore the possibility of achieving a bias-free single-step solar to chemical energy conversion using gas-phase moisture as the reactant while generating hydrogen as the reaction product. A metal-based superhygroscopic hydrogel scavenges moisture from the ambient environment and serves as the water source. The FeOOH/BiVO4 heterojunction works as the photoanode wherein the interface allows the transport of electrons to the outer layer, resulting in an upward band bending. Concomitantly, the negative charges will accumulate on the Cu2O surface in the FeOOH/Cu2O photocathode, inducing a downward band bending. With the use of the hydrogel, photoanode, and photocathode, a device for directly splitting the moisture absorbed from the ambient air is realized, generating a photocurrent of 0.75 mA cm-2 under the one-sun intensity of cool daylight without any additional bias. The solar-cell-assisted device can split 6 mg of moisture in 10 h, and the hydrogel can absorb more than 30 mg of moisture in the same period.

Optimal parameters estimation of the PEMFC using a balanced version of Water Strider Algorithm

Recently, much attention was paid to the application of renewable energy in environmental issues. Meanwhile, the fuel cell industry, which is considered an environmentally friendly industry, is one of the important components of this project. They are in fact devices for the direct conversion of chemical energy into electrical energy by an electrochemical reaction without the need for any mechanical parts. In this study, it is attempted to model one of their important types, called proton exchange membrane fuel cells, so that it can be used in predicting the behavior of the fuel cell and examining various parameters affecting the performance of the cell. The main idea is to optimal parameters estimation for the proton exchange membrane fuel cells by minimizing the total Squared Error value between the empirical output voltage and the approximated output voltage. For giving better results in terms of accuracy and reliability, a new design of a metaheuristic called the balanced Water Strider Algorithm is utilized. The results of the suggested method are finally validated by comparison with several latest optimizers applied on a practical test case. After running all of the optimizers 30 times independently, the proposed method with minimum absolute error equals 3.4831e−4 shows the best results toward the others.

(Invited) Commercialization of Catalytic Materials for Chemical and Electrochemical Energy Conversion Technologies

The incredible growth in Electrochemical Energy Conversion Technologies is leading to highly accelerated innovation in the materials at the heart of these technologies. Electrocatalysts for hydrogen generation and conversion, in particular, are experiencing an accelerated adoption cycle when compared to previous deployment, influenced both by volatility and dramatic growth (>60% annually) in precious metal prices. Pajarito Powder has developed and commercialized novel electrocatalysts for fuel cells and electrolyzers. Different applications, the path to commercialization, and both opportunities and challenges to commercialization will be presented, described, and discussed.

An experimental investigation on a novel direct-fired porous boiler for the low-pressure steam applications

Heat is the most essential form of energy for mankind lives. Steam is the most widely used as heat-carrying medium in the world. The boiler is the best system for the conversion of chemical energy contained in fuels into steam or hot fluid. According to the efficiency of all existing boilers, one of the most important factors that substantially affect this boiler performance index is the stack losses. This research proposed a novel direct-fired porous boiler (DPB). Because of it has no stack losses, this proposed boiler could outperforms all of the existing boilers. The purpose of this article is to discuss the potential of enhancing the suggested DPB performance by using different physical characteristics of packed-bed porous medium (PPM). The experimental results show that among the four most bed shapes available in the market and have a high heat transfer aspect, the hex-nut shape has been selected to use in the proposed DPB. At the heat input rate of about 14 kW, the steam generation rate of about 20 kg/h, (at 1.5 barg and 300 °C), is obtained. Because it has only surface heat loss, thermal efficiency of more than 98% can be achieved. It can be concluded that the possibility of using a hex-nut bed as a packed bed porous medium in a low-pressure porous boiler is confirmed with the proposed boiler.

Plasmonic metal/semiconductor hybrid nanomaterials for solar to chemical energy conversion

Plasmonic nanomaterials are sources of light, heat and electrons at nanometer scale. Given the outstanding performance in harvesting and converting solar energy under visible light irradiation, hybrid nanomaterials with plasmonic activity have recently emerged as a new class of advanced photocatalysts. Because of the enhanced charge-separation at hybrid interfaces, the hybrids usually exhibit higher catalytic activity compared with their monometallic counterparts. Here, we review the recent progress on synthesis of plasmonic hybrid nanomaterials and their applications in photocatalysis, including H2 production, CO2 reduction and N2 fixation. We hope this review will give systematic and valuable reference on plasmonic solar to chemical energy conversion.

Biofuel Cell-Driven Robust Electrochemiluminescence Biosensing Platform.

Electrochemiluminescence (ECL) is one powerful tool in the sensing field, in which the electrochemical workstation is necessary to achieve the electrical/optical signal conversion in the presence of luminescent agents. By contrast, biofuel cells (BFCs) can also provide electricity from renewable biofuels under moderate conditions. More importantly, BFCs with the features of adjustable voltage output and excellent compatibility would well meet the requirement of working voltages for different ECL devices. However, to the best of our knowledge, the BFC-driven luminous system has not been reported. In this work, we constructed, for the first time, a BFC-driven ECL system with fast and stable signal outputs. To demonstrate the proof-of-concept of the BFC-ECL system, the sensitive and selective detection of histidine was achieved, exhibiting great potential among point-of-care diagnoses in remote regions. Overall, this work not only paves a new way for the conversion of chemical energy, electrical energy, and luminous system but also explores the new application of BFC.

Photoelectron Photoion Coincidence Spectroscopy Provides Mechanistic Insights in Fuel Synthesis and Conversion

Clean combustion, i.e., the reduction of NOx and soot emissions, and carbon neutrality, achieved in part by biofuel synthesis, are major milestones in the transition to a sustainable future. To overcome empiric and time-consuming process optimization steps, we need detailed reaction mechanistic and chemical insights on these processes. Be it in combustion or in catalysis, highly reactive intermediates, such as radicals, carbenes, and ketenes drive chemical reactions. Knowing the fate of these species helps develop strategies to optimize chemical energy conversion processes. This calls for advanced mass spectrometric tools, which enable the detection of transient species. In this review, we report on the application of state-of-the-art photoelectron photoion coincidence (PEPICO) spectroscopy with vacuum ultraviolet (VUV) synchrotron radiation as advanced diagnostic tools in catalysis and combustion research. We discuss reaction mechanisms in biomass conversion to sustainable fuels, where we report on the pyrolysis of wood samples probed using VUV photoionization mass spectrometry (PIMS) and obtain deep mechanistic insights in the (non)catalytic pyrolysis of lignin model compounds with PEPICO detection. PEPICO is also shown to contribute to the mechanistic understanding of catalysis by unveiling catalytic alkane valorization mechanisms. We discuss how PEPICO detection advances combustion diagnostics, thanks to the application of photoelectron spectroscopy and velocity map imaging. We report on mechanistic aspects of ignition, such as fuel radical formation and oxidation to peroxy species, and discuss reaction pathways of pollutant formation. In addition, we zoom into the elementary reactions of combustion and discuss isomer-selective kinetics experiments on radical oxidation. Newly revealed reaction pathways to polycyclic aromatic hydrocarbon (PAH) formation are also detailed. Finally, we describe current instrumental developments to improve PEPICO detection and report on innovative sources, reactors, and reaction sampling approaches to be combined with this technique.

Cataluminescence in Er-Substituted Perovskites.

Thermophotovoltaic devices have promising applications for energy conversion. However, current conversion efficiency of chemical energy to light is very low, limited by the competing process of heat dissipation released as black body radiation. From a fundamental point of view, the direct conversion of chemical energy into light without this detour is possible. This so called cataluminescence from methanol combustion over Er‐substituted SrTiO3 with high efficiency is demonstrated. The catalytically active quaternary perovskites Er0.15La0.15Sr0.55Ti0.95Cu0.05O3 − δ exsolute and reabsorb metallic Cu particles onto the surface in reducing and oxidizing conditions, respectively. Thus, it is able to manipulate the surface structure and investigate its influence on the catalytic as well as luminescent properties. The fuel to air ratio around the stoichiometry point changes the conditions from reducing to oxidizing and thereby alters the surface properties. This is evidenced by post mortem X‐ray diffraction and X‐ray photoemission as well as operando optical spectroscopy. Cataluminescence takes place under oxidizing conditions (lean fuel to air mixture) on the Er‐perovskite oxide with a strong selective near infrared emission, while reducing conditions stimulate formation of plasmonic Cu‐nanoparticles, which emit black body radiation.

Mechanochemistry for Energy Materials: Impact of High-Energy Milling on Chemical, Electric and Thermal Transport Properties of Chalcopyrite CuFeS2 Nanoparticles.

Chalcopyrite CuFeS2, a semiconductor with applications in chemical sector and energy conversion engineering, was synthetized in a planetary mill from elemental precursors. The synthesis is environmentally friendly, waste‐free and inexpensive. The synthesized nano‐powders were characterized by XRD, SEM, EDX, BET and UV/Vis techniques, tests of chemical reactivity and, namely, thermoelectric performance of sintered ceramics followed. The crystallite size of ∼13 nm and the strain of ∼17 were calculated for CuFeS2 powders milled for 60, 120, 180 and 240 min, respectively. The evolution of characteristic band gaps, Eg, and the rate constant of leaching, k, of nano‐powders are corroborated by the universal evolution of the parameter SBET/X (SBET ‐specific surface area, X‐crystallinity) introduced for complex characterization of mechanochemically activated solids in various fields such as chemical engineering and/or energy conversion. The focus on non‐doped semiconducting CuFeS2 enabled to assess the role of impurities, which critically and often negatively influence the thermoelectric properties.

Expanding the scope of antenna–reactor photocatalysts for strong visible light absorption in small transition metal nanoparticles

The design of antenna–reactor photocatalysts has become a powerful strategy to covert transition metal reactors from traditional thermocatalysts to novel photocatalysts. Plasmonic metals are often used as the optical antenna. Here, we demonstrate that conventional dielectric supports with high refractive index are able to achieve comparable performance as the plasmonic antennas, giving rise to a huge enhancement of the visible light absorption in the small Pt nanoparticles (NPs) of the core–satellite antenna–reactor photocatalysts through resonance energy transfer. The absorption enhancement can be mediated not only by the electric resonances of the plasmonic antenna but also by the magnetic resonances of the dielectric antenna. A large enough dielectric antenna or a small plasmonic antenna is desired for the generation of strong optical resonances. Judged by those Pt NPs with strong visible light absorption enhancement, the potential catalytically active sites are mainly distributed at the back side of the dielectric antenna, while they may be widely distributed over the surface of the plasmonic antenna with probably lower activities. The expanding scope of antenna–reactor photocatalysts offers new opportunities for solar to chemical energy conversion using nonplasmonic catalytic transition metals.