DeCarbon最新文献

The dominant factor for hot electron collecting in internally photoemitted hot carrier (IPHC) devices is still not clear under steady-state low intensity light. We here use SnO₂ as the electron-collecting layer to replace TiO₂ to construct IPHC devices. Almost no photoresponse is observed for the pure SnO₂-based IPHC device. However, when an insulating MgO layer or TiO₂ covered SnO₂, relatively large photocurrent generated from hot electrons can be achieved. The effective electron mass (EEM) is figured out to be the dominate factor in hot electron collection in IPHC devices. The very small EEM of SnO₂ results in a small emission cone of hot electrons. Also due to the small EEM of SnO₂, the leakage of trapped electrons back to the Au is very large. Because of these two reasons, the SnO₂-based IPHC device shows almost no photoresponse. MgO can block the backflow of electrons (leakage), while the larger EEM of TiO₂ can increase the emission cone of hot electrons. Our finding is significant for understanding hot electrons collection and will give new directions for hot carrier solar cell applications under low-intensity excitation at steady state.

Latent heat thermal energy storage techniques based on phase change materials (PCMs) play a vital role in efficient and stable utilization of intermittent solar and thermal energy sources. However, low thermal conductivity and poor mechanical strength are daunting bottlenecks of traditional PCMs, inhibiting their wide applications. Here, we successfully enhance both thermal conductivity and mechanical robustness of porous SiC-based composite phase change materials (CPCMs) via doping MXene into SiC skeletons, which are superior to state-of-the-art ceramic CPCMs. The thermal conductivity of MXene-doped CPCMs achieves 15.21 ​W/(m·K) at a porosity of 72.9%, which is 25% higher than that of undoped counterparts. The underlying mechanism lies in that the oxide layer on the surface of MXene melts at a high temperature, filling the gap between SiC grains and optimizing the thermal transport path. Compared with virgin SiC skeletons, the flexural strength and compressive strength of MXene-doped skeletons are enhanced by 20% and 29%, respectively. This is because MXene removed from the oxide layer disperses in the ceramic matrix and improves the mechanical strength of the composite through pull-out, crack deflection and the change of fracture mode. Superior cycle stability and thermal shock resistance are also demonstrated. High thermal conductivity, robust mechanical strength, exceptional stability, and high solar absorptance enable prepared composites to realize high-performance dual-functional thermal and solar energy storage.

Agriculture is considered a hard to abate sector in which 2050 net-zero greenhouse gas (GHG) emissions targets will be challenging. Anaerobic digestion is a technology that can reduce agricultural emissions whilst producing renewable energy and a biofertiliser. In Ireland this technology was previously evaluated to be a high cost of abatement solution. However, it is not clear if the potential variations in anaerobic digestion systems were accounted for in these analyses; scale, plant design, technology, feedstock and biogas end-use differ between systems and can directly impact abatement costs. This study assesses different biogas end-use options (generation of heat, electricity and biomethane) and varying farm sizes for on-farm anaerobic digestion systems digesting grass silage and cattle slurry feedstocks. To evaluate and compare each biogas end-use for the varying farm sizes, the abatement cost and potential was obtained based on the net present value (NPV) and the total discounted GHG emissions for each system configuration. The abatement cost of the on-farm anaerobic digestion systems assessed varied between −7 €/tCO_2eq to 816 €/tCO_2eq. For a farm with 185 dairy cows, the integration of anaerobic digestion with the use of a boiler to produce heat sold through a district heating network was found to be a financially viable option. Biogas upgrading to produce biomethane was not financially viable due to the high operational and capital costs of small-scale upgrading systems. A key result of the analysis shows that if a single input variable is changed within the system boundary, the financial and environmental performance of a system can be significantly changed. For example, an increase in tariffs and biomethane sale prices can substantially improve the financial viability from +72 €/tCO_2eq to −227 €/tCO_2eq. Similarly, a higher cost for grass silage feedstock (€43 per tonne) will unfavourably impact the abatement cost; raising it from −7 €/tCO_2eq to 492 €/tCO_2eq.

Low-temperature thermal energy (<130 °C) recycling and utilization can significantly increase energy efficiency and reduce CO₂ emissions. Among various technologies for heat-to-electricity conversion, thermally regenerative electrochemical cycle (TREC) has garnered significant attention for remarkable efficiency in thermal energy utilization. The thermally regenerative electrochemical cycled flow battery (TREC-FB) in this paper offers several advantages, including continuous power output and operating without an external power supply. The goal of this investigation is to enhance the understanding of how various parameters affect system performance through simulation, thus optimizing cell performance. In this work, based on the conservation equations and electrochemical equations, the two-dimensional steady models coupled with the flow field and electrochemical field of high-temperature cell and low-temperature cell are constructed separately by COMSOL Multiphysics. The diffusion coefficient and kinetic parameters in the model were obtained by cyclic voltammetry (CV), chronoamperometry (CA) and Tafel electrochemical measurements for subsequent application in the models. Experimental results have confirmed the validity of this model. The main focus of this work is to examine how the system performance is impacted by various factors including current density, electrolyte flow rate, temperature coefficient, porous electrode geometry, heat recuperation efficiency, and temperature difference between hot and cold cells. The results indicate that a larger electrolyte flow rate leads to larger power density, but reduces system efficiency. Smaller porous electrode thickness, higher temperature coefficient, higher heat recuperation efficiency and larger temperature difference between the cells can enhance the system performance. This work offers a new guide for further enhancing TREC-FB performance.

It is of great significance to develop novel heat-harvesting technology due to abundant waste heat on earth. Although thermoelectric generators (TEGs) based on the Seebeck effect under temperature gradient has been studied for more than 200 years, their thermoelectric (TE) performance is still not good enough for large-scale practical application. Ionic TE materials can exhibit much higher thermovoltage than electronic conductors, but they can be used to harvest heat merely from temperature fluctuation. In order to take the advantages of these two types of TE materials, we developed flexible combinatorial TE converters (CTECs) with an ionic TE capacitor (ITEC) made of an ionogel and a TEG consisted of poly (3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS), which were connected in parallel, that is, the electrodes of the ITEC and TEG at the hot end are wired together, while those at the cold end are connected. These CTECs can harvest heat from both temperature gradient by the TEG and temperature fluctuation by the ITEC. Their TE performances are sensitive to the factors like heating/cooling rates, temperature gradient profile and internal resistance of the TEG. The specific average power supplied by the CTEC can be up to 4.7 times as that of the control TEG with PEDOT:PSS. Moreover, the TE performance can be further improved by combining an ITEC with a TEG consisted of both p- and n-type legs in series, which can generate a specific average power as 5.8 times as the CTECs with the TEG of only one p-type leg.

Hygroscopic dopant in hole transport layer (HTL) is a key factor contributing to moisture-induced perovskite degradation and the resulting performance loss over time. This poses obstacles to the commercialization of perovskite solar cells (PSCs). Herein, we mixed two popular hole transport materials, i.e., [2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9′-spirobifluorene] (Spiro-OMeTAD) and poly (3-hexylthiophene-2,5-diyl) (P3HT), to form a binary mixed HTL. Due to the presence of hydrophobic P3HT component, the mixed HTL exhibits improved moisture resistance. In addition, P3HT demonstrates a great ability to interact with the dopants, which changes π-π packing orientation of P3HT from edge-on to face-on and improves its crystallinity, thus increasing hole mobility and hole extraction capability of the mixed HTL. As a result, PSCs equipped with the Spiro-OMeTAD/P3HT mixed HTL exhibit a champion power conversion efficiency (PCE) up to 24.3% and superior operational stability. The cells without encapsulation can maintain 90% initial efficiency after storage in dark ambient conditions (30% RH) for 1200 ​h. These results suggest that constructing Spiro-OMeTAD/P3HT mixed HTL is a promising strategy to meet the future photovoltaic applications demands with low-cost as well as excellent efficiency and device stability.