During the operation of proton exchange membrane fuel cell (PEMFC), about half of the energy is dissipated as heat. To enhance the energy efficiency of fuel cell electric vehicle (FCEV), we hereby ...propose a waste heat recovery system for low-temperature energy harvesting of FCEV. A comprehensive fluid-thermal-electrical multiphysics model is established to predict the performance of the proposed thermoelectric generator (TEG) system. Subsequently, a practical prototype of TEG system is developed. Transient and steady-state experimental results from the prototype validated the feasibility and power generation efficiency of the TEG system. At a temperature difference of 40°C, the highest open circuit voltage and power output of each TEG are 6.2V and 0.33W respectively, the results affirmatively demonstrate that the TEG system can recover the low temperature waste heat from PEMFC, thus providing valuable guidance for the design of the future PEMFC thermal management system in FCEV.
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•A novel waste heat recovery system is proposed•Effect of power generation is studied through the numerical model•The heat recovery feasibility of the TEG system verified by prototype experiment•It has guiding significance for the design of the fuel cell’s thermal management
Applied sciences; Engineering; Devices
Ultrasound-driven bioelectronics could offer a wireless scheme with sustainable power supply; however, current ultrasound implantable systems present critical challenges in biocompatibility and ...harvesting performance related to lead/lead-free piezoelectric materials and devices. Here, we report a lead-free dual-frequency ultrasound implants for wireless, biphasic deep brain stimulation, which integrates two developed lead-free sandwich porous 1-3-type piezoelectric composite elements with enhanced harvesting performance in a flexible printed circuit board. The implant is ultrasonically powered through a portable external dual-frequency transducer and generates programmable biphasic stimulus pulses in clinically relevant frequencies. Furthermore, we demonstrate ultrasound-driven implants for long-term biosafety therapy in deep brain stimulation through an epileptic rodent model. With biocompatibility and improved electrical performance, the lead-free materials and devices presented here could provide a promising platform for developing implantable ultrasonic electronics in the future.
Designing high-efficiency and low-cost catalysts with high current densities for the oxygen evolution reaction (OER) is critical for commercial seawater electrolysis. Here, we present a heterophase ...synthetic strategy for constructing an electrocatalyst with dense heterogeneous interfacial sites among crystalline Ni2P, Fe2P, CeO2, and amorphous NiFeCe oxides on nickel foam (NF). The synergistic effect of high-density crystalline and amorphous heterogeneous interfaces effectively promotes the redistribution of the charge density and optimizes the adsorbed oxygen intermediates, lowering the energy barrier and promoting the O2 desorption, thus enhancing the OER performance. The obtained NiFeO-CeO2/NF catalyst exhibited outstanding OER catalytic activity, with low overpotentials of 338 and 408 mV required to attain high current densities of 500 and 1000 mA cm–2, respectively, in alkaline natural seawater electrolytes. The solar-driven seawater electrolysis system presents a record-setting and stable solar-to-hydrogen conversion efficiency of 20.10%. This work provides directives for developing highly effective and stable catalysts for large-scale clean energy production.
The mass transfer and related electrochemical reactions in the catalytic layer (CL) are crucial for the performance of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), but there ...is a lack of understanding of the optimal phosphoric acid content and Pt/C catalyst loading in the CL. In this work, we investigate the influences of Pt/C catalyst numbers (NPt/C) and phosphoric acid film thickness (δPA) on mass transfer and electrochemical reactions of the cathode CL using a pore-scale model (300 × 300 × 300 nm3). The results reveal that larger NPt/C and δPA can impede oxygen diffusion, while lower NPt/C and δPA lead to fewer reaction active sites and lower conductivity, both of which result in lower current density. Therefore, the balance of three-phase transport is extremely important for CL. There is a 3D volcanic relationship between current density, Pt/C catalysts, and phosphoric acid film. At NPt/C = 200 (7407 per μm3) and δPA = 4 nm (the volume fractions of 37.22 % and 17.87 %), the highest current density can be achieved at a potential of 0.5 V (vs. RHE), which increased with the decrease of potential. This work is valuable for understanding the optimizing the microstructure and three-phase transport pathway of the CL to improve the performance of HT-PEMFCs.
•Catalyst layer is reconstructed numerically in a HT-PEMFCs with a pore-scale model.•The influence of Pt/C catalyst number and phosphoric acid film thickness is studied.•The balance between the three phases of the transmission pathway is very important.•A 3D volcano-shaped relationship is obtained to describe the current density, NPt/C and δPA.
•Transpiration of P. sylvestris increased with increasing tree age.•Seasonal water use pattern differed markedly among different aged P. sylvestris.•Older P. sylvestris increased absorption of deep ...soil water and groundwater.•Aggravated soil drying and faster groundwater decline occurred in the oldest stand.
Understanding the water use pattern and transpiration rate of revegetation species is crucial for efficient water management and sustainable vegetation restoration. Mongolian pine (P. sylvestris) plantation has been implemented for decades in desert regions of northwest China, achieving significant improvements in combating soil erosion and desertification. However, the characteristics of water use pattern and transpiration of P. sylvestris at different ages remain poorly understood. We investigated seasonal variations in water uptake pattern and transpiration of different-aged P. sylvestris (4-, 10-, and 18-yr) based on stable isotope and sap flow measurements over two growing seasons. The canopy transpiration of P. sylvestris and its discrepancy between the dry and rainy season increased with increasing stand age. The 4-yr P. sylvestris extracted water mainly from shallow soil layer (0–120 cm) across the growing season (63.21–69.40%). In contrast, the older P. sylvestris (10- and 18-yr) displayed a greater degree of ecological plasticity as they shifted water uptake to deeper soils and groundwater in times of drought. In the rainy season, 10-, and 18-yr P. sylvestris extracted water predominantly from shallow soil layer (68.62%) and shallow plus middle soil layers (0–200 cm) (66.04%), respectively; in the dry season, however, they both shifted main water sources to the middle plus deep soil layers (120–300 cm) (61.29% and 63.45%). The older P. sylvestris also increased absorption of groundwater in the dry season, leading to more severe soil desiccation and faster groundwater decline. The changes in water use patterns of P. sylvestris were related to differences in root distribution and biomass, seasonal variations of plant transpiration, and changes in soil water condition. As a consequence, the variations and controls of age-dependent plant water uptake and transpiration should be considered to implement the corresponding management measures in future reforestation activities to achieve sustainable development goals.
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•Cosmic-ray neutron probe is applicable in alpine meadow ecosystems.•TS of SWC existed in alpine meadow on the northern Tibetan Plateau.•SWC of TS representative locations can represent the field ...mean with high accuracy.•TS method has a high accuracy in deep-scaling CRNP-estimated SWC.
Soil moisture is a key limiting factor in grass growth and restoration in alpine meadow ecosystems on the northern Tibetan Plateau. In the deeper layers, soil moisture influences the processes of freeze-thaw, erosion and water cycle. Cosmic-ray neutron probe (CRNP) is a new method for continuously monitoring mean soil water content (SWC) at hectometer scale, which has been applied in an alpine meadow at a high accuracy. However, with CRNP measuring depth of only 30cm, depth-scaling is needed for sufficient insight into deep-layer soil moisture. This study evaluated the accuracy of CRNP measurement of SWC in the 2015 and 2016 growing seasons and the performance of temporal stability (TS) analysis in depth-scaling CRNP-estimated SWC. During the study period, 11 field samplings were done for calibration of CRNP-estimated SWC. Using 22 occasions of neutron probe measurements for each of 113 investigated locations, the TS of SWC was analyzed and its performance in depth-scaling CRNP-estimated SWC at five soil depths (10, 20, 30, 40 and 50cm) was evaluated. The results showed that the mean SWCs to the depth of 50cm were 12.9 and 17.0%, respectively in 2015 and 2016 growing seasons and were temporally influenced by precipitation and spatially by soil depth. The accuracy of the CRNP-measured SWC was high, with root mean square error and Nash-Sutcliffe efficiency coefficient (NSE) of 2.1% and 0.832, respectively. Representative locations for TS existed in all the soil layers, which increased with increasing soil depth. For the various soil layers, TS-estimated SWC was close to field-measured value. Only a relatively small error and high NSE were noted, suggesting that TS was reliable in application in CRNP depth-scaling. The study provided further scientific basis for the application of CRNP and an effective way of depth-scaling CRNP-estimated mean SWC in alpine meadow ecosystems.
Wettability in CO2-brine-mineral/rock systems is an important parameter influencing CO2 storage capacities and leakage risks in saline reservoirs. However, CO2 tends to react with various minerals ...and rocks at subsurface conditions, thus causing temporal and spatial wettability changes. Although many relevant research works have been published during past years, a thorough overview of this area is still lacking. Therefore herein, reaction-induced wettability changes are reviewed, and the underlying mechanisms are discussed. Current research gaps are identified, future outlooks are suggested, and some conclusions are drawn. The fundamental understanding of reaction-induced mineral and rock wettability changes during CO2 storage in saline reservoirs is analyzed and the guidance for long-term CO2 containment security evaluations is provided.
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•A novel nano-heterostructure is fabricated via a facile solvothermal method.•The novel intercrossed heterostructure could enhance the light utilization and charge separation.•The ...Z-scheme heterojunction could decrease the recombination loss of photogenerated charge carriers.•The synergistic effect of intercrossed heterostructure and Z-scheme heterojunction ensures the excellent photoelectrochemical performance of CuInS2/TiO2 photoanode.
Photoelectrochemical (PEC) water splitting serves as an intriguing strategy for solar energy storage and conversion, but still suffers from the poor efficiency. In this work, a Z-scheme heterostructure comprised of CuInS2 nanosheets and TiO2 nanorods with an intercrossed structure was fabricated. Boosted by the well-matched structure, the as-prepared CuInS2/TiO2 hybrid achieved a high photo-electrocatalytic hydrogen evolution rate of 12.4 µmol/h, which was16 times greater than pure TiO2, owing to more effective solar energy utilization and interfacial photocarrier separation. Furthermore, PEC studies demonstrated that the novel hybrid offered a much higher photocurrent density than the nanoparticle counterpart, which could be ascribed to the elevated separation efficiencies of the photogenerated electron-hole pairs, and accompanied by efficient charge carrier transport. Based on the obtained results, this work provided a potential and promising approach for the fabrication of photo-electrocatalyst, which may inspire additional mechanism research of PEC and photo-electrocatalytic systems with hierarchical architecture.
•The measuring radius of the CRNS was 580m in the AME.•The measuring depth of the CRNS was ca. 31cm in the AME.•The accuracy of the CRNS in monitoring SWC was high in the AME.•Diurnal fluctuation of ...hourly SWC measured by the CRNS was discernable.
Cosmic-ray neutron sensing (CRNS) is a new method for continuously monitoring mean soil water content (SWC) on a hectometer scale. To evaluate the application and accuracy of the method for SWC observation in an alpine meadow ecosystem (AME), we installed the CRNS in a flat meadow near the Naqu prefecture on the northern Tibetan Plateau. We collecting soil samples and applying the system by the oven-drying method. A weather station was also installed near the CRNS for monitoring basic meteorological variables and the soil temperature and water content at various depths. Three Em-50 instruments for monitoring SWC and soil temperature were buried in three sub-quadrats northwest, northeast and southeast of the CRNS at distances of 460, 370 and 373m, respectively, to observe the variation of SWC at the various depths. The footprint of the CRNS for SWC observation in the meadow was about 580m, and the mean measuring depth was about 31cm according to the general calculation equations. The reference neutron flux for dry soil (N0) had a mean and coefficient of variation of 8686 and 3%, respectively, and remained substantially invariant throughout the measuring period. The five SWCs from the independent field samples almost passed through the SWC trend of the CRNS, the root mean square error (RMSE) was 0.011m3m−3 for the CRNS and oven-drying method. The time series of SWC measured by the CRNS agreed well with the mean SWC series to a depth of 20cm measured by the weather station. The trend of SWC measured by the Em-50s generally agreed with the trend of SWC measured by the CRNS, but some values and variations of SWC differed between the Em-50s and CRNS data. Because of the good agreement between the CRNS and independent field samples, we suspect that this disagreement is due to an insufficient representativeness of point observations and the distances of the points from the CRNS. The diurnal variation of hourly SWC from the CRNS was sinusoidal during a dry period, peaking at 11:00 and was minimum at 18:00 (Beijing time), with a range of 1%. Overall, the CRNS measured SWC in the AME with an acceptable accuracy, providing a scientific basis for the promotion and application of the CRNS in high, cold ecosystems.
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