Frontiers in Energy

Xue, Jing; Chen, Zhenlin; Zhang, Yuchao; Zhao, Jincai

2024 Frontiers in Energy

doi: 10.1007/s11708-024-0950-8

Utilizing plasmonic effects to assist electrochemical reactions exhibits a huge potential in tuning the reaction activities and product selectivity, which is most appealing especially in chemical reactions with multiple products, such as CO2 reduction reaction (CO2RR). However, a comprehensive review of the development and the underlying mechanisms in plasmon-assisted electrocatalytic CO2RR remains few and far between. Herein, the fundamentals of localized surface plasmonic resonance (LSPR) excitation and the properties of typical plasmonic metals (including Au, Ag, and Cu) are retrospected. Subsequently, the potential mechanisms of plasmonic effects (such as hot carrier effects and photothermal effects) on the reaction performance in the field of plasmon-assisted electrocatalytic CO2RR are summarized, which provides directions for the future development of this field. It is concluded that plasmonic catalysts exhibit potential capabilities in enhancing CO2RR while more in situ techniques are essential to further clarify the inner mechanisms.

Gong, Feng; Jing, Yuhang; Xiao, Rui

2024 Frontiers in Energy

doi: 10.1007/s11708-024-0949-1

Ammonia, with its high hydrogen storage density of 17.7 wt.% (mass fraction), cleanliness, efficiency, and renewability, presents itself as a promising zero-carbon fuel. However, the traditional Haber–Bosch (H–B) process for ammonia synthesis necessitates high temperature and pressure, resulting in over 420 million tons of carbon dioxide emissions annually, and relies on fossil fuel consumption. In contrast, dielectric barrier discharge (DBD) plasma-assisted ammonia synthesis operates at low temperatures and atmospheric pressures, utilizing nitrogen and hydrogen radicals excited by energetic electrons, offering a potential alternative to the H-B process. This method can be effectively coupled with renewable energy sources (such as solar and wind) for environmentally friendly, distributed, and efficient ammonia production. This review delves into a comprehensive analysis of the low-temperature DBD plasma-assisted ammonia synthesis technology at atmospheric pressure, covering the reaction pathway, mechanism, and catalyst system involved in plasma nitrogen fixation. Drawing from current research, it evaluates the economic feasibility of the DBD plasmaassisted ammonia synthesis technology, analyzes existing dilemmas and challenges, and provides insights and recommendations for the future of nonthermal plasma ammonia processes.

Lei, Cong; Yang, Rongzhong; Zhao, Jianan; Tang, Wenbin; Miao, Fadong; Huang, Qinghong; Wu, Yuping

2024 Frontiers in Energy

doi: 10.1007/s11708-024-0928-6

In this study, the Lewis doping approach of polyaniline (PANI) was employed to fabricate cobait–nitrogen–carbon (Co-N-C) oxygen electrocatalysts for Zn–air batteries, aiming to enhance the active spots of Co-N-C. This resulting Co-N-C catalysts exhibited well-defined nanofiber networks, and the Brunauer-Emmett-Teller (BET) analysis confirmed their substantial specific surface area. Electrochemical experiments demonstrated that the Co-N-C catalysts achieved the half-wave potential (vs. RHE) of 0.85 V in alkaline medium, overcoming Pt/C and iron–nitrogen–carbon (Fe-N-C) counterparts in extended cycle testing with only a 25 mV change in a half-wave potential after 5000 cycles. Remarkably, the highest power density measured in the zinc (Zn)–air battery reached 227 mW/cm2, a significant improvement over the performance of 101 mW/cm2 of the platinum on activated carbon (Pt/C) catalyst. These findings highlight the advantageous stability enhancement associated with the utilization of Co in the Co-N-C catalysts.

Wei, Zhiyuan; Liu, Changying; Sun, Xiaowen; Li, Yiduo; Lu, Haiyan

2024 Frontiers in Energy

doi: 10.1007/s11708-023-0906-4

Lithium-ion batteries (LIBs) are widely used in transportation, energy storage, and other fields. The prediction of the remaining useful life (RUL) of lithium batteries not only provides a reference for health management but also serves as a basis for assessing the residual value of the battery. In order to improve the prediction accuracy of the RUL of LIBs, a two-phase RUL early prediction method combining neural network and Gaussian process regression (GPR) is proposed. In the initial phase, the features related to the capacity degradation of LIBs are utilized to train the neural network model, which is used to predict the initial cycle lifetime of 124 LIBs. The Pearson coefficient’s two most significant characteristic factors and the predicted normalized lifetime form a 3D space. The Euclidean distance between the test dataset and each cell in the training dataset and validation dataset is calculated, and the shortest distance is considered to have a similar degradation pattern, which is used to determine the initial Dual Exponential Model (DEM). In the second phase, GPR uses the DEM as the initial parameter to predict each test set’s early RUL (ERUL). By testing four batteries under different working conditions, the RMSE of all capacity estimation is less than 1.2%, and the accuracy percentage (AP) of remaining life prediction is more than 98%. Experiments show that the method does not need human intervention and has high prediction accuracy.

Qu, Hongyu; Xu, Xiaoyu; Hong, Longfei; Wang, Xintie; Zan, Yifei; Zhang, Huiyan; Zhang, Xiao; Chu, Sheng

2024 Frontiers in Energy

doi: 10.1007/s11708-023-0910-8

Polyimide (PI) has emerged as a promising organic photocatalyst owing to its distinct advantages of high visible-light response, facile synthesis, molecularly tunable donor-acceptor structure, and excellent physicochemical stability. However, the synthesis of high-quality PI photoelectrode remains a challenge, and photoelectrochemical (PEC) water splitting for PI has been less studied. Herein, the synthesis of uniform PI photoelectrode films via a simple spin-coating method was reported, and their PEC properties were investigated using melamine as donor and various anhydrides as acceptors. The influence of the conjugate size of aromatic unit (phenyl, biphenyl, naphthalene, perylene) of electron acceptor on PEC performance were studied, where naphthalene-based PI photoelectrode exhibited the highest photocurrent response. This is resulted from the unification of wide-range light absorption, efficient charge separation and transport, and strong photooxidation capacity. This paper expands the material library of polymer films for PEC applications and contributes to the rational design of efficient polymer photoelectrodes.

Gong, Feng; Song, Jiaming; Chen, Haotian; Li, Hao; Huang, Runnan; Jing, Yuhang; Yang, Peng; Feng, Junjie; Xiao, Rui

2024 Frontiers in Energy

doi: 10.1007/s11708-024-0930-z

With the development of renewable energy technologies, the recovery and utilization of low-grade energy based on hydroelectric effect have drawn much attention owing to its environmental friendliness. Herein, a novel hydroelectric generator utilizing sodium alginate-graphene oxide (SA-GO) fibers is proposed, which is ecofriendly and low-cost. These fibers with a length of 5 cm and a diameter of 0.15 mm can generate an open circuit voltage (Voc) of approximately 0.25 V and a short circuit current (Isc) of 4 µA. By connecting SA-GO fibers in either series or parallel, this combination can power some electronic devices. Furthermore, these fibers enable the recovery of low-grade energy from the atmosphere or around the human body. Both experimental and theoretical analysis confirm that the directional flow of protons driven by water molecules is the main mechanism for power generation of SA-GO fibers. This study not only presents a simple energy transformation method that is expected to be applied to our daily life, but also provides a novel idea for the design of humidity electricity-generation devices.

Wiesmann, Frederik; Qiu, Zeyan; Han, Dong; Strauβ, Lukas; Rieβ, Sebastian; Wensing, Michael; Lauer, Thomas

2024 Frontiers in Energy

doi: 10.1007/s11708-024-0926-8

For a climate-neutral future mobility, the so-called e-fuels can play an essential part. Especially, oxygenated e-fuels containing oxygen in their chemical formula have the additional potential to burn with significantly lower soot levels. In particular, polyoxymethylene dimethyl ethers or oxymethylene ethers (PODEs or OMEs) do not contain carbon-carbon bonds, prohibiting the production of soot precursors like acetylene (C2H2). These properties make OMEs a highly interesting candidate for future climate-neutral compression-ignition engines. However, to fully leverage their potential, the auto-ignition process, flame propagation, and mixing regimes of the combustion need to be understood. To achieve this, efficient oxidation mechanisms suitable for computational fluid dynamics (CFD) calculations must be developed and validated. The present work aims to highlight the improvements made by developing an adapted oxidation mechanism for OME1−6 and introducing it into a validated spray combustion CFD model for OMEs. The simulations were conducted for single- and multi-injection patterns, changing ambient temperatures, and oxygen contents. The results were validated against high-pressure and high-temperature constant-pressure chamber experiments. OH*-chemiluminescence measurements accomplished the characterization of the auto-ignition process. Both experiments and simulations were conducted for two different injectors. Significant improvements concerning the prediction of the ignition delay time were accomplished while also retaining an excellent agreement for the flame lift-off length. The spatial zones of high-temperature reaction activity were also affected by the adaption of the reaction kinetics. They showed a greater tendency to form OH* radicals within the center of the spray in accordance with the experiments.

Zhou, Dengji; Hao, Jiarui; Xiao, Wang; Wang, Chen; Shui, Chongyuan; Jia, Xingyun; Yan, Siyun

2024 Frontiers in Energy

doi: 10.1007/s11708-023-0914-4

For the purpose of environment protecting and energy saving, renewable energy has been distributed into the power grid in a considerable scale. However, the consuming capacity of the power grid for renewable energy is relatively limited. As an effective way to absorb the excessive renewable energy, the power to gas (P2G) technology is able to convert excessive renewable energy into hydrogen. Hydrogen-blending natural gas pipeline is an efficient approach for hydrogen transportation. However, hydrogen-blending natural gas complicates the whole integrated energy system (IES), making it more problematic to cope with the equipment failure, demand response and dynamic optimization. Nevertheless, dynamic simulation of distribution parameters of gas–electricity–hydrogen (GEH) energy system, especially for hydrogen concentration, still remains a challenge. The dynamics of hydrogen-blending IES is undiscovered. To tackle the issue, an iterative solving framework of the GEH-IES and a cell segment-based method for hydrogen mixing ratio distribution are proposed in this paper. Two typical numerical cases studying the conditions under which renewables fluctuate and generators fail are conducted on a real-word system. The results show that hydrogen blending timely and spatially influences the flow parameters, of which the hydrogen mixing ratio and gas pressure loss along the gas pipeline are negatively correlated and the response to hydrogen mixing ratio is time-delayed. Moreover, the hydrogen-blending amount and position also have a significant impact on the performance of the compressor.

Niu, Juntian; Chen, Shengzhuo; Zheng, Xianrong; Liu, Haiyu; Jin, Yan; Ran, Jingyu

2024 Frontiers in Energy

doi: 10.1007/s11708-024-0952-6

In recent years, the dry reforming of methane (DRM) reaction has gained widespread attention due to its effective utilization of two major greenhouse gases. Supported Ni-based catalysts for DRM exhibit a strong dependence on particle size, however, the reaction mechanisms involved remain unclear. In this work, the effect of metal particle size on CO2 activation and CO formation was explored in the DRM reaction using the density functional theory. Nix/MgO (x = 13, 25, 37) was constructed to investigate the CO2 activation and the formation of CO during the DRM reaction. It is found that CO2 is more inclined to undergo chemisorption on Nix/MgO before activation. With the variation in particle size, the main activation pathway of CO2 on the catalyst changes. On the smallest Ni13/MgO, CO2 tends to directly dissociate, while on the larger Ni25/MgO and Ni37/MgO, the hydrogenation dissociation of CO2 is more kinetically favorable. Compared to Ni13/MgO and Ni37/MgO, the oxidation of surface C atoms and the oxidation of CH occur more readily on Ni25/MgO. This indicates that C atoms are less likely to form on Ni25 particle and are more easily to be oxidized. To some extent, the results suggest that Ni25/MgO exhibits superior resistance to carbon formation.

Shadike, Zulipiya; Chen, Yiming; Liu, Lin; Cai, Xinyin; Shen, Shuiyun; Zhang, Junliang

2024 Frontiers in Energy

doi: 10.1007/s11708-024-0953-5

The undesired side reactions at electrode/electrolyte interface as well as the irreversible phase evolution during electrochemical cycling significantly affect the cyclic performances of nickel-rich NMCs electrode materials. Electrolyte optimization is an effective approach to suppress such an adverse side reaction, thereby enhancing the electrochemical properties. Herein, a novel boron-based film forming additive, tris(2,2,2-trifluoroethyl) borate (TTFEB), has been introduced to regulate the interphasial chemistry of LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode to improve its long-term cyclability and rate properties. The results of multi-model diagnostic study reveal that formation lithium fluoride (LiF)-rich and boron (B) containing cathode electrolyte interphase (CEI) not only stabilizes cathode surface, but also prevents electrolyte decomposition. Moreover, homogenously distributed B containing species serves as a skeleton to form more uniform and denser CEI, reducing the interphasial resistance. Remarkably, the Li/NMC811 cell with the TTFEB additive delivers an exceptional cycling stability with a high-capacity retention of 72.8% after 350 electrochemical cycles at a 1 C current rate, which is significantly higher than that of the cell cycled in the conventional electrolyte (59.7%). These findings provide a feasible pathway for improving the electrochemical performance of Ni-rich NMCs cathode by regulating the interphasial chemistry.