High Energy Conversion Efficiency Research Articles

Experiment-Validated multiphysics modeling, generalizable deep learning and interpretable global sensitivity analyses for thermoelectric generators

Despite extensive studies on thermoelectric materials in a thermoelectric generator (TEG), the inverse design of TEG operating conditions remains challenging. Recent efforts in deep learning of TEGs using artificial neural network (ANN) lack global sensitivity analyses and interpretation of the connection-weights, leading to unknown coupling between input parameters and errors in importance ranking. This work reports a deep learning framework for TEGs using generalizable ANN, interpretable local (LSA) and global sensitivity analyses (GSA). Sensitivity analyses are applied to determine how energy conversion efficiency (η) under the practical Neumann and Robin thermal boundary conditions is affected by TEG operating conditions, including hot-side heat flux (qh), cold-side convective heat transfer coefficient (hf), temperature of the cooling medium (Ta), load resistance (RL), electric contact resistance (Rc), and thermal contact resistance (Kc). First, multiphysics TEG simulation results based on 3D finite element method (FEM) are validated by our experimental measurements using a self-built TEG performance evaluation system. The partial derivative-based LSA is done on a 1D theoretical TEG model to obtain the trend in sensitivity factors. Then, an ANN model is trained and validated based on the FEM simulation results and applied to the GSA process, aiming at reducing the computational load. Variance-based GSA is applied on the ANN model to determine the importance ranking and reflect the coupling between input parameters. The variance-based GSA ranks the importance as qh>hf>RL>Ta≈Rc≈Kc, and reflects the coupling between qh and hf. Finally, to interpret the ANN and the hidden deep learning process, a method combining the connection-weights algorithm and neural interpretation diagram (NID) is proposed to extract the hidden information in the connection weights. The ANN model is proven generalizable towards larger ranges of operating conditions. This work provides a framework to design TEG operating conditions towards higher energy conversion efficiencies.

Advances in Blue Energy Fuels: Harvesting Energy from Ocean for Self‐Powered Electrolysis

Abstract70% of the earth's surface is covered by the ocean, and it represents a promising and renewable clean energy reservoir that waits for further exploration. Although hydrogen (H2) boasts a high energy density of 143 MJ kg−1 and environmentally friendly attributes, the widespread commercialization of green H2 production remains a formidable challenge. With huge amounts of water, the ocean presents an opportunity for generating H2 fuel through the process of seawater electrolysis. This review introduces ocean‐driven, self‐powered blue energy conversion devices, including triboelectric nanogenerators (TENGs), magnetoelastic generators (MEGs), and solar cells. They are able to convert renewable energy from the ocean, including water waves, wind, and solar energy, into electricity for on‐site seawater‐splitting and H2 generation. This review systematically reports this compelling approach by introducing the fundamental principles of the devices and showcasing the practical applications. Additionally, aiming to promote future research in the field of sustainable energy, this review also delves into the development of novel ocean energy harvesting systems with high energy conversion efficiency for large‐scale and effective H2 production.

Comprehensive analysis on three-phase imbalance management technology of low-voltage distribution network

Energy production and use is one of the major sources of global greenhouse gas emissions. To combat climate change, many countries and organizations are pushing to reduce the use of fossil fuels, and the use of renewable energy sources such as solar, wind, and hydro is growing rapidly. The conversion of these renewable energy into electricity requires a large amount of power electronics. Power electronics have higher energy conversion efficiency, greater adjustability and control, and smaller size and weight than traditional generators. These characteristics make power electronic equipment have a wide range of application prospects in the field of energy conversion and power control. There may be cost, reliability, debugging, and three-phase imbalance issues. Based on the harm of three-phase imbalance to the economic operation and safe and stable operation of distribution network, the importance of three-phase imbalance in low-voltage distribution network is expounded, and the relationship between three-phase unbalance current and power factor is elaborated on the construction of three-phase imbalance. Reduce the harm of three-phase imbalance to the distribution network and reduce the loss of distribution network lines.

Dual-network fiber-hydrogel membrane for osmotic energy harvesting.

Osmotic energy harvesting was a promising way to alleviate energy crisis with reverse electrodialysis (RED) membrane-based technology. Charged hydrogel combined with other materials was an effective strategy to overcome problems, including restricted functional groups and complicated fabrication, but the effect of the respective charges of the two materials combined on the membrane properties has rarely been studied in depth. Herein, a new method was proposed that charged hydrogel was equipped with charged filter paper to form dual network fiber-hydrogel membrane for osmotic energy harvesting, which had excellent ion selectivity (beyond 0.9 under high concentration gradient), high ion transference number and energy conversion efficiency (beyond 32.5% under wide range concentration gradient), good property of osmotic energy conversion (∼4.84W/m2 under 50-fold KCl and ∼6.75W/m2 under simulated sea water and river water). Moreover, the power density was attributed to the surface-space charge synergistic effect from large amounts overlapping of electric double layer (EDL), so that the transmembrane ion transport was enhanced. It might be a valid mode to extensively develop the osmotic energy harvesting.

Flexible Janus Black Silicon Photothermal Conversion Membranes for Highly Efficient Solar-Driven Interfacial Water Purification.

Photothermal conversion materials are critical in the development of solar-driven interfacial evaporation techniques; however, achieving a high energy conversion efficiency remains challenging owing to the high cost and instability of light-absorbing materials, in addition to the difficulties of simultaneously improving light absorption while suppressing heat loss. A black silicon (Si) powder with a porous structure was prepared by chemical etching of a low-cost commercial micron-sized Al-Si alloy, and a flexible Janus black Si photothermal conversion membrane was constructed. The partially broken spherical particles and porous structure obtained after etching enhanced the refraction of light from the Si powder, imparting the prepared membrane with an average light absorption rate of 95.95% over the solar spectrum. Evaporation from the membrane increased the intermediate water content and reduced the equivalent evaporation enthalpy. The thermal conduction loss was inhibited through a one-dimensional water transport structure, and the membrane achieved a water evaporation rate of 2.17 kg m-2 h-1 and a photothermal efficiency of 94.95% under 1 sun illumination. Benefiting from the broadband absorption and high photothermal efficiency of black Si powder, surface modification of hydrophobic polydimethylsiloxane, and directional salt-out structure design, the evaporation rate of the Janus black Si membrane-based system in a 10% NaCl solution was maintained >2.10 kg m-2 h-1 after 7 days of continuous evaporation cycles. The removal rate of metal ions from simulated seawater and from practical wastewater containing complex heavy metals reached >99.9%, indicating the promising potential of black Si membrane for application in solar-driven interfacial water purification.

Cr3+‐doped far‐red phosphors with zero thermal quenching and excellent spectral matching for plant lighting application

AbstractFar‐red‐emitting (700−740 nm) phosphors are essential for the fabrication of plant lighting phosphor‐converted light‐emitting diodes (pc‐LEDs). However, the development of highly efficient, thermally stable, and spectrally matched far‐red phosphors still remains a challenge. Herein, far‐red GdAlO3:Cr3+ (GAO:Cr3+) phosphors were synthesized via solid‐state reaction and investigated for plant lighting pc‐LED applications. A low‐temperature flux‐assisted synthesis strategy was adopted to improve the crystalline quality, suppress the defect formation, and maintain the valence state of Cr3+ in the phosphors, finally leading to significant luminescent enhancement (∼10 times). The GAO:Cr3+ phosphors show the 2E sharp‐line emissions around 730 nm, which is highly matched with the far‐red absorption band of plants. The optimized GAO:0.01Cr3+ phosphor exhibits a high internal quantum efficiency of 98.3% and zero thermal quenching even up to 250°C. The fabricated pc‐LED can generate an overall output power of 78.1 mW at 100 mA drive current, with a high energy conversion efficiency of 25.3%. The findings demonstrate the great potential of GAO:Cr3+ as far‐red‐emitting phosphor materials for plant growth pc‐LED applications.

Optimal strategy of the asymmetric wave energy converter survival in extreme waves

Enhancing the survival performance of wave energy converters (WECs) in extreme wave conditions is crucial, and reducing wave loads is a key aspect of this. Placing the device underwater has been recognized as a beneficial strategy, yet the determination of the optimal submerged depth and the effects of varying wave conditions remain ambiguous. To address this, the study numerically analyzes the total forces in both horizontal and vertical directions, along with their harmonic components, across different wave configurations. A computational fluid dynamics method is employed to investigate a triangular-baffle bottom-shaped oscillating floater, which is known for its high energy conversion efficiency. The findings indicate that submerging the device to a depth equivalent to half the actual focused amplitude (1/2Ab) is the most effective strategy in the given sea state, offering superior wave force reduction vertically and robust performance horizontally. The analysis of harmonics reveals the significant contribution of high-order components to the total wave forces. Additionally, the study examines the impact of focused wave amplitudes and peak frequencies, showing that although force reductions are lessened in more extreme conditions, the optimal submerged depth of 1/2Ab still yields near 30% reduction in total vertical force and 22% in total horizontal force. This research provides theoretical insight that can guide the enhancement of WECs' survival capabilities in practical engineering applications.

Control-inspired design and power optimization of an active mechanical motion rectifier based power takeoff for wave energy converters

Ocean waves have high energy density and are persistent and predictable. Yet, converting wave energy to a useable form remains challenging. A significant hurdle is the oscillatory nature of waves resulting in the alternating loads, which necessitate the use of rectification at some stage of the energy conversion. This research effort presents a novel design of active mechanical motion rectifier (AMMR) for the power takeoff (PTO), which provides enhanced controllability and better power performance when compared to passive mechanical motion rectifiers (MMR). Inspired by transistors used in synchronous electrical rectifiers, the proposed design uses controllable electromagnetic clutches in the mechanical transmission to allow active engagement-disengagement control; thus, rectifying the oscillatory motion into a unidirectional rotation for high energy conversion efficiency and allowing the generator in unidirectional rotation to control the bidirectional wave capture structure for maximizing the power output. A semi-analytical computational approach is developed to efficiently evaluate the optimal power achieved using the proposed AMMR-based PTO and active control. It is found that the AMMR-based PTO design yields a higher optimal power than the previous passive MMR design across the wave spectrum. The influences of generator inertia and reactive power are discussed. The effects of control parameters on the power output and the optimal trajectories are analyzed. Wave tank tests with the AMMR prototype demonstrated the effectiveness of AMMR based PTO design and validated the numerical analysis.

Shaping the Future of the Neurotransmitter Sensor: Tailored CdS Nanostructures for State-of-the-Art Self-Powered Photoelectrochemical Devices.

Semiconductor-based photoelectrochemical (PEC) test protocols offer a viable solution for developing efficient individual health monitoring by converting light and chemical energy into electrical signals. However, slow reaction kinetics and electron-hole complexation at the interface limit their practical application. Here, we reported a triple-engineered CdS nanohierarchical structures (CdS NHs) modification scheme including morphology, defective states, and heterogeneous structure to achieve precise monitoring of the neurotransmitter dopamine (DA) in plasma and noninvasive body fluids. By precisely manipulating the Cd-S precursor, we achieved precise control over ternary CdS NHs and obtained well-defined layered self-assembled CdS NHs through a surface carbon treatment. The integration of defect states and the thin carbon layer effectively established carrier directional transfer pathways, thereby enhancing interface reaction sites and improving the conversion efficiency. The CdS NHs microelectrode fabricated demonstrated a remarkable negative response toward DA, thereby enabling the development of a miniature self-powered PEC device for precise quantification in human saliva. Additionally, the utilization of density functional theory calculations elucidated the structural characteristics of DA and the defect state of CdS, thus establishing crucial theoretical groundwork for optimizing the polymerization process of DA. The present study offers a potential engineering approach for developing high energy conversion efficiency PEC semiconductors as well as proposing a novel concept for designing sensitive testing strategies.

Carbon and economic prices optimization of a solar-gas coupling energy system with a modified non-dominated sorting genetic algorithm considering operating sequences of water-cooled chillers

To promote the continuous operating of solar energy systems and increase the proportion of renewable energy consumption, solar devices are often integrated with conventional energy systems to reduce greenhouse gas emissions. In this study, a solar-natural gas coupling system is constructed, utilizing solar photovoltaics, thermal collectors, and high-efficiency energy conversion devices. After modelling the energy system, the operating modes are illustrated considering working sequences of water-cooled devices. A modified genetic algorithm, which incorporates reverse learning, controlled elite, and dynamic crowding distance theory, is constructed to optimize the configurations of the proposed energy system, with the aim of minimizing carbon and economic prices of the products. The performance of the energy system is compared with different algorithms and cases, and the results demonstrate that the proposed optimization algorithm addresses the limitations of conventional methods, albeit with increased optimization times. Moreover, the proposed operating mode (Case 1) exhibits a stable performance, leading to a higher environmental and economic performance compared to conventional modes, with carbon and economic prices of 0.242 kg/kWh and 0.067 $/kWh, respectively. This study provides new insights into carbon footprints and economic performance evaluation of high-efficiency energy systems, offering valuable directions for future research in this field.

Manipulation of Nonradiative Process Based on the Aggregation Microenvironment to Customize Excited-State Energy Conversion.

ConspectusNonradiative processes with the determined role in excited-state energy conversion, such as internal conversion (IC), vibrational relaxation (VR), intersystem crossing (ISC), and energy or electron transfer (ET or eT), have exerted a crucial effect on biological functions in nature. Inspired by these, nonradiative process manipulation has been extensively utilized to develop organic functional materials in the fields of energy and biomedicine. Therefore, comprehensive knowledge and effective manipulation of sophisticated nonradiative processes for achieving high-efficiency excited-state energy conversion are quintessential. So far, many strategies focused on molecular engineering have demonstrated tremendous potential in manipulating nonradiative processes to tailor excited-state energy conversion. Besides, molecular aggregation considerably affects nonradiative processes due to their ultrasensitivity, thus providing us with another essential approach to manipulating nonradiative processes, such as the famous aggregation-induced emission. However, the weak interactions established upon aggregation, namely, the aggregation microenvironment (AME), possess hierarchical, dynamic, and systemic characteristics and are extremely complicated to elucidate. Revealing the relationship between the AME and nonradiative process and employing it to customize excited-state energy conversion would greatly promote advanced materials in energy utilization, biomedicine, etc., but remain a huge challenge. Our group has devoted much effort to achieving this goal.In this Account, we focus on our recent developments in nonradiative process manipulation based on AME. First, we provide insight into the effect of the AME on nonradiative process in terms of its steric effect and electronic regulation, illustrating the possibility of nonradiative process manipulation through AME modulation. Second, the distinct enhanced steric effect is established by crystallization and heterogeneous polymerization to conduct crystallization-induced reversal from dark to bright excited states and dynamic hardening-triggered nonradiative process suppression for highly efficient luminescence. Meanwhile, promoting the ISC process and stabilizing the triplet state are also manipulated by the crystal and polymer matrix to induce room-temperature phosphorescence. Furthermore, the strategies employed to exploit nonradiative processes for photothermy and photosensitization are reviewed. For photothermal conversion, besides the weakened steric effect with promoted molecular motions, a new strategy involving the introduction of diradicals upon aggregation to narrow the energy band gap and enhance intermolecular interactions is put forward to facilitate IC and VR for high-efficiency photothermal conversion. For photosensitization, both the enhanced steric effect from the rigid matrix and the effective electronic regulation from the electron-rich microenvironment are demonstrated to facilitate ISC, ET, and eT for superior photosensitization. Finally, we explore the existing challenges and future directions of nonradiative process manipulation by AME modulation for customized excited-state energy conversion. We hope that this Account will be of wide interest to readers from different disciplines.

Effects of Mechanical and Electrical Topologies on Piezoelectric Stacked Energy Harvesting in Vehicle Suspensions

The choice of mechanical and electrical topologies can affect piezoelectric energy harvesting efficiency, but the problem of achieving high-efficiency energy conversion in energy harvesters stacked as cantilevers has not been perfectly solved. This study focuses on the topology of piezoelectric elements in a stacked vehicle suspension vibration energy harvesting device. Through theoretical analysis, the stress expressions of the excited and driven elements are derived. The stress of the piezoelectric elements is affected by the positions of the connection and excitation points. A stress model was established for a four-piece piezoelectric element connected by a thin light rod in ANASYS. The simulation results show that the average stress in the piezoelectric bending element model is maximum when the excitation and connection points are located at both ends of the free end. Compared with the middle position of the free end of the piezoelectric element, the average stress of the model is increased by 92.904%. Considering the difference in voltage generated by piezoelectric elements, four kinds of electrical topology are designed and analyzed experimentally. When the driven elements are connected in parallel and then connected in series with the excited element, the output power varied the least with the change of load resistance. The system produces a high power and offers a wide selection of load resistors. When the load is 26 kΩ, a single set of four piezoelectric elements produces 86.407 mW of output power.

Bioinspired binary-site catalysts for novel urea-assisted Zn-air battery: A transfer station between renewable energy and hydrogen

The slow reaction kinetics of oxygen electrode is the bottleneck restricting the development of rechargeable Zn-air batteries (ZABs). In order to further improve the energy conversion efficiency of ZABs, a novel urea-assisted ZAB system was proposed by replacing oxygen evolution reaction (OER) with urea oxidation reaction (UOR) with lower theoretical thermodynamic potential. Inspired by nature’s ingenious structure-function, a “leaf-branch” CoNi@NCNTs-LDH/CC binary-site electrocatalyst was designed for the above system, where spatially separated branches and leaves serve as the main active sites for ORR and UOR, respectively. A build-in electric field from CoNi-LDH to CoNi@NCNTs is formed at the interface of the composite, which plays a command effect, effectively triggering the accumulation of O2 and urea reactants around the CoNi and LDH sites, respectively, and thus improving the efficiency of both ORR and UOR reactions. Based on that, a conceptual urea-assisted rechargeable ZAB is demonstrated to have significantly decreased charging voltage, higher energy conversion efficiency (74.6 %) compared with the conventional ZAB, as well as high urea elimination rates. Considering the urea-assisted ZAB with high energy conversion efficiency and wastewater treatment versatility as an energy transfer station applied in a high value-added agricultural system, uninterrupted hydrogen production and wastewater treatment of agricultural wastewater can be simultaneously achieved using sustainable energy sources.

Effect of Ni Doping on the Thermoelectric Properties of YbCo2Zn20.

Thermoelectric devices are both solid-state heat pumps and energy generators. Having a reversible process without moving parts is of high importance for applications in remote locations or under extreme conditions. Yet, most thermoelectric devices have a rather limited energy conversion efficiency due to the natural competition between high electrical conductivity and low thermal conductivity, both being essential conditions for achieving a high energy conversion efficiency. Heavy-fermion compounds YbT2Zn20 (T = Co, Rh, Ir) have been reported to be potential candidate materials for thermoelectric applications at low temperatures. Motivated by this result, we applied chemical substitution studies on the transition metal site in order to optimize the charge carrier concentration as well as promote more efficient phonon scatterings. Here, we present the latest investigation on the Ni-doped specimens YbCo2-xNixZn20, where enhanced thermoelectric figure of merit values have been obtained.

Enhanced Open-Circuit Voltage Subject to Harmonic Excitations in Piezoelectric Energy Harvesters Using Hybrid Optimization Algorithm

In this manuscript, a hybrid method is proposed to attain the piezo-electric energy harvesters (PEHs) with an improved conversion of energy effectiveness or open-circuit voltage. The proposed method is the joint execution of Pelican Optimization Algorithm (POA) and Dwarf Mongoose Optimizer (DMO) named as POA-DMO technique. The primary goal of the planned POA's design is to simulate pelicans’ typical hunting activity. By topologically improving piezo-electric distribution through the thickness of materials, such as piezo-electric energy harvester plates are based on the harmonic excitations and open-circuit-voltage of PEHs is increased. The efficacy of the energy conversion and the open-circuit-voltage are taken into account as the design goals. For the two taken into consideration design objectives, the arrangement of the piezo-electric material in the thickness direction is topologically optimal. In order to produce more electricity, the piezoelectric materials are positioned in the regions of increased stress/strain and high energy conversion efficiency. To acquire more electric power while maintaining a constant electric resistance, the distribution of piezo-electric materials is calibrated to determine the frequency of external stimulation frequency in order to realize a high open-circuit voltage. The proposed method performance is done in MATLAB and it is compared with existing approaches.

Sulfonated poly(ether ether ketone)-Protic ionic Liquid-Based anhydrous Proton-Conducting composite polymer electrolyte membranes for High-Temperature fuel cell applications

A high-temperature polymer electrolyte membrane fuel cell (PEMFC) has enormous potential to produce clean energy with minimal environmental pollution along with high energy density and conversion efficiency. In the present work, anhydrous proton-conducting polymer electrolyte membranes for prospective high-temperature fuel cell application were successfully prepared using different protic ionic liquids (PILs) and sulfonated poly(ether ether ketone) (SPEEK). The protic ionic liquids (PILs), 2-hydroxyethylammonium formate, diethylmethyl ammonium triflate, 1-ethylimidazolium bis(trifluoromethylsulfonyl)imide, 1,2-dimethyl imidazolium bis(trifluoro methylsulfonyl)imide, and diethylmethylammonium methanesulfonate were selected based on their favorable physicochemical properties. The effect of the incorporation of the PIL on the structural, thermal, and electrical transport properties of the composite SPEEK polymer electrolyte membranes was studied. The prepared polymer electrolyte membranes (PEMs) were characterized using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and electrochemical impedance spectroscopy (EIS) techniques. FTIR results indicated an interaction between the PIL and the SPEEK, which resulted in homogeneous and flexible membranes. The DSC results confirmed good miscibility and elucidated plasticizing effect of the incorporated PIL on the SPEEK polymer matrix. All the PEMs showed good thermal stability and high-temperature anhydrous proton conductivity, achieving best proton conductivity, ≈8 × 10–3 S cm−1 at 120 °C and low activation energy ≈0.26 eV, making it suitable for prospective high-temperature PEMFC applications.

Advances in the development of few-cycle gigawatt-peak-power mid-IR optical parametric amplifiers pumped by Cr:Forsterite laser using non-oxide nonlinear crystals

We demonstrate an experimental and theoretical comparison of non-oxide LiGaS2, HgGa2S4, and AgGaS2 crystals performance for wavelength conversion into the near and mid-IR range 1.5–8 μm in optical parametric amplifier pumped by Cr:Forsterite laser, delivering 100 fs pulses at 1.24 μm. It is shown that exceptionally high total energy conversion efficiency into the idler (4–5 μm) and signal (1.65–1.8 μm) waves up to 18% can be achieved using the HGS crystal, providing high nonlinearity, while the LGS crystal is more preferable for generating few-cycle mid-IR pulses due its unique dispersive properties. Our source features high peak power in gigawatt regime (0.4–2.4 GW) with pulse duration below 80 fs and optical synchronization with high harmonic generation (HHG) and THz beamlines, which is ideal for pump-probe experiments of nonlinear and strong-field physics.

Interface Engineering to Operate Reversible Protonic Ceramic Electrochemical Cells Below 500 °C

AbstractThe low‐temperature (<500 °C) operation of reversible protonic ceramic electrochemical cells (PCECs) is desirable in achieving efficient and sustainable electricity generation, as well as green hydrogen production. However, significant interfacial resistance, which contributes to both ohmic and polarization resistance, remains a hurdle in lowering the operating temperature. In this study, PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) and BaZr0.4Ce0.4Y0.1Yb0.1O3‐δ (BZCYYb) mono‐grain composite interlayers are introduced, which significantly extend the electrode/electrolyte interface and increase the concentration of vertically aligned oxygen vacancies along the heterointerface. This unique design achieves the lowest ohmic and polarization resistances among previously reported values in solid electrolyte‐based electrochemical cells. As a result, the PCEC can operate at extremely low temperature of 350 °C with an exceptional peak power density of 0.50 W cm−2 in fuel cell mode and current density of 0.25 A cm−2 at 1.3 V in electrolysis cell mode. Furthermore, it demonstrates high energy conversion efficiency and excellent stability under static and dynamic operating conditions.

3D-honeycomb architectures evaporator toward mutual reinforcement of evaporation and catalysis for efficient freshwater harvesting

Solar-driven freshwater harvesting has emerged as an effective and sustainable technology to mitigate global water scarcity due to its high energy conversion efficiency. Nevertheless, achieving mutual reinforcement of photothermal and photocatalysis processes is in high demand because the contamination of harmful and highly concentrated volatile organic compounds (VOCs) will inevitably evaporate and condense alongside water. Herein, an integrated 3D-honeycomb fabric (NPPF) evaporator decorated with polydopamine (PDA), polypyrrole (PPy), and hydrotalcite (LDH) nanoflowers was designed innovatively by synergistically cooperating photothermal evaporation and advanced catalytic oxidation techniques. With periodically concave arrays, it can create the maximum level of light-trapping through multiple scattering and omnidirectional light absorption, thereby increasing its photothermal catalytic degradation ability. Meanwhile, introducing the LDH nanoflowers boosted the photothermal evaporation capacity of the NPPF evaporator. Therefore, it demonstrated high solar absorption efficiency of ∼98.02% and an evaporation rate of ∼2.02 kg m−2 h−1 under one sun. Furthermore, it can achieve superb degradation activity, especially for high-concentration VOCs, with efficiency of ∼93.99%, surpassing most of the other evaporators reported previously. Besides, the outdoor experiment demonstrated its practicability. More importantly, it can remove tetracycline and phenol with efficiency of ∼98.85% and ∼ 92.06%. The advantages make this evaporator a promising representative for cooperative freshwater production.

Efficient water recovery and power generation system based on air-cooled fuel cell with semi-closed cathode circulation mode

Air-cooled proton exchange membrane hydrogen fuel cell with on-line hydrogen production by hydrolysis has potential for portable applications due to its high volumetric power density and self-humidification. However, plenty of reserve water significantly reduces the power density of fuel cell system. Moreover, water recovery from fuel cell tail gas is difficult, because the tail gas humidity is very low due to excess cathode air as coolant. In this work, the dead-ended anode and semi-closed cathode proton exchange membrane fuel cell is proposed to achieve efficient water recovery and energy conversion via semi-closed cathode circulation mode. In this mode, cathode O2-poor tail gas is recycled as coolant instead of fresh air, which helps to enlarge the tail gas humidity by reducing the stoichiometric ratio of cathode to anode gas. The system lumped model with detailed component description is developed for optimization. >96% water production can be recycled under atmosphere temperature. The demand of fresh air is greatly reduced from 56 to 2 times of the consumption. Besides, the multi-objective optimization between water recovery and electrochemical performance shows high-efficiency water recovery of 94.70% and high energy conversion efficiency of 54.82%.