Sustainable Energy Conversion Research Articles

Construction of NiFe/MnNiCo-LDH heterostructure for enhanced oxygen evolution reaction for efficient water splitting

Developing highly efficient and cost-effective oxygen evolution reaction (OER) catalysts is pivotal for advancing sustainable energy storage and conversion technologies. Herein, NiFe/MnNiCo-LDH was successfully prepared by in-situ growth method. The OER performance of this composite material had been significantly enhanced through bimetallic atom modification and cation doping strategies. These modifications not only enhanced the electronic conductivity but also regulated the electron distribution within the catalyst structure. As a result, NiFe/MnNiCo-LDH can reach a current density of 10 mA cm−2 at an overpotential of only 227 mV in the OER reaction. Moreover, the catalyst exhibited remarkable durability and maintained its high performance over an extended period of 48 h during the water splitting reaction. In this work, the potential of dual modification methods for optimizing catalytic properties of OER materials was investigated.

Dynamic Active Sites in Electrocatalysis

In‐depth understanding of the real‐time behaviors of active sites during electrocatalysis is essential for the advancement of sustainable energy conversion. Recently, the concept of dynamic active sites has been recognized as a potent approach for creating self‐adaptive electrocatalysts that can address a variety of electrocatalytic reactions, outperforming traditional electrocatalysts with static active sites. Nonetheless, the comprehension of the underlying principles that guide the engineering of dynamic active sites is presently insufficient. In this review, we systematically analyze the fundamentals of dynamic active sites for electrocatalysis and consider important future directions for this emerging field. We reveal that dynamic behaviors and reversibility are two crucial factors that influence electrocatalytic performance. By reviewing recent advances in dynamic active sites, we conclude that implementing dynamic electrocatalysis through variable reaction environments, correlating the model of dynamic evolution with catalytic properties, and developing localized and ultrafast in‐situ/operando techniques are keys to designing high‐performance dynamic electrocatalysts. This review paves the way to the development of the next‐generation electrocatalyst and the universal theory for both dynamic and static active sites.

Dynamic Active Sites in Electrocatalysis.

In-depth understanding of the real-time behaviors of active sites during electrocatalysis is essential for the advancement of sustainable energy conversion. Recently, the concept of dynamic active sites has been recognized as a potent approach for creating self-adaptive electrocatalysts that can address a variety of electrocatalytic reactions, outperforming traditional electrocatalysts with static active sites. Nonetheless, the comprehension of the underlying principles that guide the engineering of dynamic active sites is presently insufficient. In this review, we systematically analyze the fundamentals of dynamic active sites for electrocatalysis and consider important future directions for this emerging field. We reveal that dynamic behaviors and reversibility are two crucial factors that influence electrocatalytic performance. By reviewing recent advances in dynamic active sites, we conclude that implementing dynamic electrocatalysis through variable reaction environments, correlating the model of dynamic evolution with catalytic properties, and developing localized and ultrafast in-situ/operando techniques are keys to designing high-performance dynamic electrocatalysts. This review paves the way to the development of the next-generation electrocatalyst and the universal theory for both dynamic and static active sites.

Recent Advances in the Large‐Scale Production of Photo/Electrocatalysts for Energy Conversion and beyond

AbstractPhotocatalysis and electrocatalysis have emerged as promising technologies for addressing the energy crisis and environmental issues. However, the widespread application of these technologies is hampered by the challenge of scaling up the production of photo/electrocatalysts that are not only highly active and stable but also cost‐effective and environmentally benign. This review delves into the latest advancements in the large‐scale synthesis of photo/electrocatalysts. The factors to be considered in the large‐scale production of catalysts are discussed first. The synthesis methods for batch preparation of photo/electrocatalysts are then comprehensively introduced, with a thorough discussion of their respective advantages and limitations. Moreover, the data analysis via machine learning techniques, which not only accelerates the identification and refinement of potential new catalysts but also offers insights for enhancing the high‐throughput synthesis of catalysts, is introduced in detail. Then the representative examples are presented to illustrate the applications of large‐scale catalysts in the field of industrial‐level photo/electrocatalysis. Finally, the challenges and prospects in the development of large‐scale production of photo/electrocatalysts are discussed. By bridging the gap between laboratory research and industrial application, this review aims to provide a reference for the future of large‐scale preparation of photo/electrocatalysts in sustainable energy conversion and beyond.

Recommended practice for measurement and evaluation of oxygen evolution reaction electrocatalysis

AbstractThe Oxygen evolution reaction (OER) is a pivotal technology driving next‐generation sustainable energy conversion and storage devices. Establishing a robust analytical methodology is paramount to fostering innovation in this field. This review offers a comprehensive discussion on measurement and interpretation, advocating for standardized protocols and best practices to mitigate the myriad factors that complicate analysis. The initial focus is directed toward substrate electrodes and gas bubbles, both significant contributors to reduced reliability and reproducibility. Subsequently, the review focuses on intrinsic activity assessment, identification of electrochemical active sites, and the disentanglement of competing process contributions. These careful methodologies ensure the systematic delivery of insights crucial for assessing OER performance. In conclusion, the review highlights the critical role played by precise measurement techniques and unbiased activity comparison methodologies in propelling advancements in OER catalyst development.image

Advancing flexible thermoelectrics for integrated electronics.

With the increasing demand for energy and the climate challenges caused by the consumption of traditional fuels, there is an urgent need to accelerate the adoption of green and sustainable energy conversion and storage technologies. The integration of flexible thermoelectrics with other various energy conversion technologies plays a crucial role, enabling the conversion of multiple forms of energy such as temperature differentials, solar energy, mechanical force, and humidity into electricity. The development of these technologies lays the foundation for sustainable power solutions and promotes research progress in energy conversion. Given the complexity and rapid development of this field, this review provides a detailed overview of the progress of multifunctional integrated energy conversion and storage technologies based on thermoelectric conversion. The focus is on improving material performance, optimizing the design of integrated device structures, and achieving device flexibility to expand their application scenarios, particularly the integration and multi-functionalization of wearable energy conversion technologies. Additionally, we discuss the current development bottlenecks and future directions to facilitate the continuous advancement of this field.

Zero-Dimensional Carbon Nanomaterials: Building Blocks for Efficient Energy Conversion

Low-dimensional carbon-based materials, including 0D fullerene, 1D carbon nanotube, and 2D graphene, have been widely used as electroactive building blocks for sustainable energy conversion heterostructure nanosystems. These materials have unique physical and chemical properties at the nanoscale, such as high conductivity, high specific surface area, and tunable electronics, making them the focus of new renewable energy technologies. In this context, 0D carbon-based nanomaterials, like fullerenes and fullertubes, have garnered substantial attention as rising star energy materials. This editorial spotlight article outlines the current advancements in the utilization of 0D-fullerene and fullertube-based nanoelectrocatalysts for energy conversion. Keywords: 0D-nanocarbons, low-dimensional heterostructures, energy conversion

Vacancy-rich heterogeneous MnCo2O4.5@NiS electrocatalyst for highly efficient overall water splitting

Alkaline water electrolysis is regarded as a promising technology for sustainable energy conversion. Spinel oxides have attracted considerable attention as potential catalysts because of their diverse metal valence states. However, achieving the required current densities at low voltages is a challenge due to its limited active sites and suboptimal electron transport. In this study, we present a novel bifunctional catalyst composed of MnCo2O4.5 nanoneedles grown on NiS nanosheets for water electrolysis. Remarkably, MnCo2O4.5@NiS demonstrates exceptional catalytic activity, requiring 187 and 288 mV to achieve a current density of 100 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. The impressive performance of MnCo2O4.5@NiS is demonstrated by the lower value of voltage 1.44 V needed to deliver the current density of 10 mA cm−2, which outperformed the 1.66 V required for a commercial Pt/C||RuO2 system. Detailed structure analysis and density functional theory (DFT) calculations reveal that the MnCo2O4.5@NiS heterostructure enhances electron transfer at the interface, promotes the formation of oxygen vacancies and tunes the electronic structures of Mn and Co. These findings underscore the potential of MnCo2O4.5@NiS as an efficient and cost-effective electrocatalyst for hydrogen production.

Molecular interactions of photosystem I and ZIF-8 in bio-nanohybrid materials.

Bio-nanohybrid devices featuring natural photocatalysts bound to a nanostructure hold great promise in the search for sustainable energy conversion. One of the major challenges of integrating biological systems is protecting them against harsh environmental conditions while retaining, or ideally enhancing their photophysical properties. In this mainly computational work we investigate an assembly of cyanobacterial photosystem I (PS I) embedded in a metal-organic framework (MOF), namely the zeolitic imidazolate framework ZIF-8. This complex has been reported experimentally [Bennett et al., Nanoscale Adv., 2019, 1, 94] but so far the molecular interactions between PS I and the MOF remained elusive. We show via absorption spectroscopy that PS I remains intact throughout the encapsulation-release cycle. Molecular dynamics (MD) simulations further confirm that the encapsulation has no noticeable structural impact on the photosystem. However, the MOF building blocks frequently coordinate to the Mg2+ ions of chlorophylls in the periphery of the antenna complex. High-level quantum mechanical calculations reveal charge-transfer interactions, which affect the excitonic network and thereby may reversibly change the fluorescence properties of PS I. Nevertheless, our results highlight the stability of PS I in the MOF, as the reaction center remains unimpeded by the heterogeneous environment, paving the way for applications in the foreseeable future.

Boosting oxygen reduction performance by copper-iron co-doped on ZIF-derived N-doped carbon nanotubes

Developing high-efficiency non-noble metal catalysts for the oxygen reduction reaction (ORR) is paramount for sustainable energy conversion. In this study, we proposed a Cu, Fe co-doped zeolite imidazole framework (ZIF)-derived nitrogen-doped carbon nanotubes catalyst (Cu–Fe@CNTs/NC) obtained by hydrothermal method and pyrolysis. The electrochemical results showed that Cu–Fe@CNTs/NC exhibited favorable oxygen reduction performance and good stability under alkaline electrolyte. The incorporation of Cu and Fe bimetallic dopants promoted the carbon nanotubes growth on ZIF nanosheets, and the collaborative action of Cu and Fe enhanced its ORR catalytic activity. These findings provide an innovative way to prepare high active non-platinum ORR catalysts.

Atomically dispersed ruthenium in transition metal double layered hydroxide as a bifunctional catalyst for overall water splitting

Efficient and sustainable energy conversion depends on the rational design of single-atom catalysts. The control of the active sites at the atomic level is vital for electrocatalytic materials in alkaline and acidic electrolytes. Moreover, fabrication of effective catalysts with a well-defined surface structure results in an in-depth understanding of the catalytic mechanism. Herein, a single atom ruthenium dispersed in nickel-cobalt layered hydroxide (Ru-NiCo LDH) is reported. Through the precise controlling of the atomic dispersion and local coordination environment, Ru-NiCo LDH//Ru-NiCo LDH provides an ultra-low overpotential of 1.45 mV at 10 mA cm−2 for the overall water splitting, which surpasses that of the state-of-the-art Pt/C/RuO2 redox couple. Density functional theory calculations show that Ru-NiCo LDH optimizes hydrogen evolution intermediate adsorption energies and promotes O-O coupling at a Ru-O active site for oxygen evolution, while Ni serves as the water dissociation site for effective water splitting. As a potential model, Ru-NiCo LDH shows enhanced water splitting performance with potential for the development of promising water-alkaline catalysts.

Spherical Design‐Driven Scalable Solar‐Powered Water Treatment with Salt Self‐Cleaning and Light Self‐Adaptivity

AbstractInterfacial solar evaporation, harnessing sunlight to induce water molecule evaporation, holds great promise for sustainable solar energy conversion. However, challenges such as reduced efficiency and instability due to salt accumulation, inadequate water transport, and the high cost of advanced nanostructured solar evaporators collectively hinder the sustainable and large‐scale practical use of this technology. Herein, an eco‐friendly, floatable 3D solar seawater evaporator is developed by innovatively incorporating a lightweight foam ball enclosed in a porous cellulose hydrogel. The 3D evaporator achieves a high water evaporation rate of ≈2.01 kg m−2 h−1 under 1 Sun, owing to its super high photothermal efficiency of 117.9% and efficient internal water transport channels. Even at a 0° simulated solar angle, the 3D evaporator maintains 85.8% of the evaporation rate at a 90° simulated solar angle. Moreover, the salt self‐cleaning capability is realized by the autonomous rotation caused by salt deposition. Particularly, the 3D evaporator can be fabricated over a large area and maintain seawater evaporation performance and structural integrity for 28 days. This study provides novel economically feasible and sustainable large‐scale solutions for interfacial solar‐powered seawater treatment.

Construction of a 2D/2D Vs-ZnIn2S4/Zn-TCPP heterojunction for effective charge transfer to enhance photocatalytic hydrogen evolution

The integration of inorganic and organic semiconductor components in composites has tremendous potential in photocatalysis, owing to the ultrafast photogenerated exciton dissociation and slow carrier recombination kinetics at their interfaces, which can result in enhanced photocatalytic performances. By exploiting the synergy among morphology modulation, sulfur vacancy (Vs) engineering, and close interface control, a novel inorganic–organic Vs-ZnIn2S4/ tetrakis (4-carboxyphenyl) zinc porphyrin (Zn-TCPP) composite for photocatalytic hydrogen evolution (PHE) was successfully synthesized via microwave-assisted solvothermal and self-assembly methods. The cocatalyst-free PHE rate of Vs-ZnIn2S4/Zn-TCPP (ZZT-20 %) reaches 8.997 mmol h−1 g−1 under visible light irradiation, which is 10.9, 2.2, and 67.1 times that of ZnIn2S4, Vs-ZnIn2S4, and Zn-TCPP, respectively. Moreover, the apparent quantum yield of ZZT-20 % under 420 nm monochromatic light (1.11 %) clearly exceeds that of Vs-ZnIn2S4. Testing experiments and DFT calculations revealed that the significantly enhanced PHE activity can be mainly attributed to the Z-scheme charge transfer mechanism, which greatly improves the visible light response range and redox potentials. Remarkably, Vs sites act as electron traps, inducing the vertical transport of electrons within the bulk phase and their accumulation at the surface Zn–S bonds. Simultaneously, van der Waals forces and weak hydrogen bonds between Vs-ZnIn2S4 and the Zn-TCPP interface cause the rapid migration of photogenerated electrons to Zn-TCPP. This work not only reveals new insights into the structure–property relationships of inorganic–organic Vs-ZnIn2S4 and Zn-TCPP composites, but also provides an appropriate strategy for cleaner water resourcelization and sustainable solar energy conversion.

Constructing CoP/Ni2P Heterostructure Confined Ru Sub-Nanoclusters for Enhanced Water Splitting in Wide pH Conditions.

Developing efficient electrocatalysts for water splitting is of great significance for realizing sustainable energy conversion. In this work, Ru sub-nanoclusters anchored on cobalt-nickel bimetallic phosphides (Ru-CoP/Ni2P) are constructed by an interfacial confinement strategy. Remarkably, Ru-CoP/Ni2P with low noble metal loading (33.1µgcm-2) shows superior activity for hydrogen evolution reaction (HER) in all pH values, whose turnover frequency (TOF) is 8.7, 15.3, and 124.7 times higher than that of Pt/C in acidic, alkaline, and neutral conditions, respectively. Meanwhile, it only requires the overpotential of 171 mV@10mAcm-2 for oxygen evolution reaction (OER) and corresponding TOF is 20.3 times higher than that of RuO2. More importantly, the Ru-CoP/Ni2P||Ru-CoP/Ni2P displays superior mass activity of 4017mAmgnoble metal -1 at 2.0V in flowing alkaline water electrolyzer, which is 105.1 times higher than that of Pt/C||IrO2. In situ Raman spectroscopy demonstrates that the Ru sites in Ru-CoP/Ni2P play a key role for water splitting and follow the adsorption evolution mechanism toward OER. Further mechanism studies disclose the confined Ru atom contributes to the desorption of H2 during HER and the formation of O-O bond during OER, leading to fast reaction kinetics. This study emphasizes the importance of interface confinement for enhancing electrocatalytic activity.

Investigate the utilization of novel natural photosensitizers for the performance of dye-sensitized solar cells (DSSCs)

Dye-sensitized solar cells (DSSCs) offer a promising route for sustainable energy conversion, with natural photosensitizers emerging as attractive alternatives to conventional synthetic dyes due to their abundant resources, cost-effectiveness, and eco-friendly materials. However, the efficiency of DSSC utilizing natural photosensitizer remains low. In this study, we investigate the utilization of novel natural photosensitizers extracted from gambier leaves, gambier branches, cinnamon, and petiole of tectona leaves, which contain flavonoids/tannins, chlorophyll, and anthocyanins, aiming to achieve high-performance DSSCs. Five different solvents—ethanol, isopropanol, distilled water, methanol, and Zamzam water—are explored to optimize the extraction process of the natural dyes. The doctor blade technique is employed to coat TiO2 nanomaterials onto ITO glass substrates. UV–Vis spectrophotometry and FTIR spectroscopy are used to characterize the optical properties and structural composition of the dyes, revealing that flavonoid/tannin groups are the primary compounds responsible for light harvesting. The DSSC performance is evaluated under a 30 W lamp, adjusted to light intensity of 10 mW/cm2. As a result, the DSSCs using gambier leaf extract as photosensitizer demonstrate the highest recorded efficiency of 4.71 %, with a Jsc of 2.95 mAcm−2 and a Voc of 0.64 V. These findings contribute to advancing DSSC technology by leveraging the potential of natural photosensitizers for sustainable energy conversion applications.

Waste management optimization with NLP modeling and waste-to-energy in a circular economy

This work presents a methodology integrating Non-Linear Programming (NLP) for multi-objective and multi-period optimization, addressing sustainable waste management and energy conversion challenges. It integrates waste-to-energy (WtE) technologies such as Anaerobic Digestion (AD), Incineration (Inc), Gasification (Gsf), and Pyrolysis (Py), and considers thermochemical, technical, economic, and environmental considerations through rigorous non-linear functions. Using Mexico City as a case study, the model develops waste management strategies that balance environmental and economic aims, considering social impacts. A trade-off solution is proposed to address the conflict between objectives. The economical optimal solution generates 1.79M$ with 954 tons of CO2 emissions while the environmental one generates 0.91M$ and reduces emissions by 54%, where 40% is due to gasification technology. Moreover, the environmentally optimal solution, with incineration and gasification generates 9500 MWh/day and 5960 MWh/day, respectively, demonstrates the capacity of the model to support sustainable energy strategies. Finally, this work presents an adaptable framework for sustainable waste management decision-making.

Copper-Based Metal–Organic Frameworks Applied as Electrocatalysts for the Electroreduction of Carbon Dioxide (CO2ER) to Methane: A Review

The electrochemical reduction of carbon dioxide (CO2) to methane (CH4) holds tremendous potential in mitigating greenhouse gas emissions and producing renewable fuels. Thus, this review provides a comprehensive overview of the utilization of copper-based metal–organic frameworks (Cu-MOFs) as catalysts for this transformative process. Diverse key aspects of Cu-MOFs that make them ideal candidates for CO2 reduction are discussed, including their high surface areas, tunable pore sizes, and customizable active sites. Furthermore, recent advances in the design and synthesis of Cu-MOFs tailored specifically for enhanced catalytic activity and selectivity towards CH4 production are highlighted. Additionally, mechanistic insights into the CO2 reduction process on Cu-MOF catalysts are examined. Moreover, the recent application of diverse Cu-MOFs and derived materials in electrochemical reduction systems is discussed, and future research directions and potential applications of Cu-MOFs in sustainable energy conversion technologies are outlined. Thus, this review provides valuable insights into the current state of the art and the prospects for utilizing Cu-MOFs as efficient catalysts for the electrochemical conversion of CO2 to CH4, offering a pathway towards a greener and more sustainable energy future.

Performance prediction of experimental PEM electrolyzer using machine learning algorithms

Proton exchange membrane water electrolyzer (PEMWE) is a sustainable energy conversion device that uses electrical energy to oxidize water and convert it into chemical energy (hydrogen and oxygen) and heat. Despite their numerous advantages, such as high current density, efficiency, high-purity hydrogen production, compatibility with renewable energy sources, and compact design, they have not yet matured due to durability, cost, and electrochemical performance deficiencies. Effective assessment of performance and durability is crucial for electrolyzer design and optimization. This study analyzes the electrochemical performance of PEMWE with artificial intelligence approaches using experimental data. Three different machine learning (ML) techniques − Multilayer Perceptron (MLP), Support Vector Machine (SVM), and Random Forest (RF) were trained and tested for predicting the hydrogen flowrate and current density for PEMWE using different input parameters. These input parameters include cell voltage, temperature, torque, and water flowrate. SVM was detected to be the best technique in predicting all output parameters with a Mean Absolute Error (MAE) of 0.0317 and 0.0671 for current density and hydrogen flowrate predictions in the test set, respectively. The study results show that machine-learning algorithms can optimize operational parameters in electrolyzer control systems.

Photocatalytic Synergy Between α-Bi2O3 Nanosphere and Spindle MIL-88A for Gas-Phase CO2 Reduction.

Visible light-active photocatalysts play a crucial role in gas-phase photocatalytic CO2 reduction, offering significant potential for sustainable energy conversion. Herein, we present the synthesis of spindle-shaped Iron (Fe)-based metal-organic framework (MOF) MIL-88 A, coupled with distinct α-Bi2O3 nanospheres. The α-Bi2O3/MIL88A heterostructure is formed by interacting opposite surface charges, enhancing visible-light absorption and efficient interfacial charge-carrier separation. Such low-cost photocatalysts have a 1.75 eV band gap and demonstrate enhanced efficacy in converting CO2 to CO, CH4, and H2 in water without using any sacrificial agents or noble metals compared to pristine MIL88A. In addition, in-situ Electron Spin Resonance (ESR) analyses revealed that these unique catalysts combination promoted enhanced interfacial charge dynamics, creating efficient trapping sites for photogenerated carriers. Further, in-situ Diffuse Reflectance Infrared Fourier Transfer Spectroscopy (DRIFTS) investigation elucidates the plausible reaction mechanism and provides an effective methodology for catalyst screening for CO2 photoreduction. This study offers an effective approach for synthesizing the earth-abundant heterostructure from metal oxide and low-cost MOFs, enhancing photocatalytic activity for sustainable carbon dioxide conversion into invaluable chemicals.

Fluorescence and electron transfer of Limnospira indica functionalized biophotoelectrodes

Cyanobacteria play a crucial role in global carbon and nitrogen cycles through photosynthesis, making them valuable subjects for understanding the factors influencing their light utilization efficiency. Photosynthetic microorganisms offer a promising avenue for sustainable energy conversion in the field of photovoltaics. It was demonstrated before that application of an external electric field to the microbial biofilm or cell improves electron transfer kinetics and, consequently, efficiency of power generation. We have integrated live cyanobacterial cultures into photovoltaic devices by embedding Limnospira indica PCC 8005 cyanobacteria in agar and PEDOT:PSS matrices on the surface of boron-doped diamond electrodes. We have subjected them to varying external polarizations while simultaneously measuring current response and photosynthetic performance. For the latter, we employed Pulse-Amplitude-Modulation (PAM) fluorometry as a non-invasive and real-time monitoring tool. Our study demonstrates an improved light utilization efficiency for L. indica PCC 8005 when immobilized in a conductive matrix, particularly so for low-intensity light. Simultaneously, the impact of electrical polarization as an environmental factor influencing the photosynthetic apparatus diminishes as matrix conductivity increases. This results in only a slight decrease in light utilization efficiency for the illuminated sample compared to the dark-adapted state.