milerssliu/battery-device-data-qa huggingface dataset:
Nowadays, a variety of multifunctional electrocatalysts are being developed while there is still a lack of suitable design to fully realize their multifunctionalities. Here, we propose a general, simple, two-component design of an electrolyser to replace the traditional three-component design for decoupled water splitting. Trifunctional (OER, HER and ORR) electrocatalysts (such as nickel sulfide foams with surface grown N-doped carbon nanotube arrays) are used as the gas evolution electrode to replace both the cathode and the anode, while materials with suitable redox activities (NaTi2(PO4)3 or commercial Ni(OH)2) are used as the relay electrode. In such a design, the H2/O2 evolution can be switched by reversing the current polarity, and the ORR before the HER consumes the residual O2 left in the electrolyser, guaranteeing the high purity (∼99.9%) of the as-obtained H2. With NaTi2(PO4)3 as the relay electrode and the nickel sulfide foam as the gas evolution electrode, owing to the high decoupling efficiency of the NaTi2(PO4)3 relay (97%) and the low HER/OER overpotentials of the trifunctional nickel sulfide foam, an energy conversion efficiency of up to 94.3% can be obtained for the as-assembled electrolyser at a current density of 10 mA cm−2. When combined with a commercial Si PV module with an efficiency of 14.4%, the as-designed PV-electrolysis system showed a solar-to-hydrogen conversion efficiency of up to 10.4%. Utilization of trifunctional electrocatalysts greatly reduces the complexity of the electrolyser and the overall cost for electrochemical H2 production, and these electrolysers may potentially be used to construct highly competitive water splitting systems for continuous H2 production and green energy harvesting. Our research may also bring new insights into the utilization of multifunctional electrocatalysts in other devices, such as metal–air batteries and fuel cells.

Question: What's the anode?
Therefore, the above results demonstrate the superior energy/power densities and high efficiency of the DBHF sample, which, based on the above discussions, are associated with the “fiber-in-tube” hierarchical structure, hollow and defective oxide bubbles and conductive and porous carbon network of the DBHF fibers. The combined effects of the features are favourable for the generation of more active sites, superior catalytic activities and enhanced kinetics of the DBHF cathode in the hybrid batteries.

Question: What's the cathode?
Answer: DBHF
To better understand the good cycling stability of the full cell in the Na–H2O–urea–DMF electrolyte, inductively coupled plasma emission spectrometry-atomic emission spectroscopy (ICP-AES) analysis of the vanadium concentration in the Na–H2O–urea–DMF electrolyte and analysis of electrochemical impedance parameters were carried out before and after cycling. As shown in Fig. 4b and Table S3,† it is found that the concentration of V-ions in the Na–H2O–urea–DMF electrolyte before cycling is 0.05 μg mL−1. After 50 cycles and after 100 cycles, the concentrations of V-ions in the Na–H2O–urea–DMF electrolyte are 16.65 μg mL−1 and 20.12 μg mL−1, respectively. In 1 M Na2SO4 solution, the concentrations of V-ions are 0.08 μg mL−1, 60.68 μg mL−1 and 72.34 μg mL−1, respectively. Compared to 1 M Na2SO4 solution, the Na–H2O–urea–DMF electrolyte can obviously inhibit the dissolution of the electrode materials. Upon comparison of the V-ion concentrations in NaClO4 solution, Na–H2O–DMF, and Na–H2O–urea electrolyte of the NVP//NTP full cell after 50 cycles (Fig. S14†), it is found that the Na–H2O–urea–DMF electrolyte can suppress the dissolution of V-ions in the charge–discharge process. This result is consistent with the cycling performances of the NVP//NTP full cell in different electrolytes (Fig. S13†). Thus, it can be concluded that the NVP/C cathode is much more stable in the Na–H2O–urea–DMF electrolyte, which is beneficial for the long lifespan of the full cell. Similarly, as illustrated in Fig. S15,† the NTP anode in the Na–H2O–urea–DMF electrolyte displays high coulombic efficiency and good cycling stability relative to that in 17 M NaClO4 and 1 M Na2SO4 solution.

Question: What's the cathode?
Answer: NVP/C
To better understand the good cycling stability of the full cell in the Na–H2O–urea–DMF electrolyte, inductively coupled plasma emission spectrometry-atomic emission spectroscopy (ICP-AES) analysis of the vanadium concentration in the Na–H2O–urea–DMF electrolyte and analysis of electrochemical impedance parameters were carried out before and after cycling. As shown in Fig. 4b and Table S3,† it is found that the concentration of V-ions in the Na–H2O–urea–DMF electrolyte before cycling is 0.05 μg mL−1. After 50 cycles and after 100 cycles, the concentrations of V-ions in the Na–H2O–urea–DMF electrolyte are 16.65 μg mL−1 and 20.12 μg mL−1, respectively. In 1 M Na2SO4 solution, the concentrations of V-ions are 0.08 μg mL−1, 60.68 μg mL−1 and 72.34 μg mL−1, respectively. Compared to 1 M Na2SO4 solution, the Na–H2O–urea–DMF electrolyte can obviously inhibit the dissolution of the electrode materials. Upon comparison of the V-ion concentrations in NaClO4 solution, Na–H2O–DMF, and Na–H2O–urea electrolyte of the NVP//NTP full cell after 50 cycles (Fig. S14†), it is found that the Na–H2O–urea–DMF electrolyte can suppress the dissolution of V-ions in the charge–discharge process. This result is consistent with the cycling performances of the NVP//NTP full cell in different electrolytes (Fig. S13†). Thus, it can be concluded that the NVP/C cathode is much more stable in the Na–H2O–urea–DMF electrolyte, which is beneficial for the long lifespan of the full cell. Similarly, as illustrated in Fig. S15,† the NTP anode in the Na–H2O–urea–DMF electrolyte displays high coulombic efficiency and good cycling stability relative to that in 17 M NaClO4 and 1 M Na2SO4 solution.

Question: What's the anode?
Answer: NTP
To better understand the good cycling stability of the full cell in the Na–H2O–urea–DMF electrolyte, inductively coupled plasma emission spectrometry-atomic emission spectroscopy (ICP-AES) analysis of the vanadium concentration in the Na–H2O–urea–DMF electrolyte and analysis of electrochemical impedance parameters were carried out before and after cycling. As shown in Fig. 4b and Table S3,† it is found that the concentration of V-ions in the Na–H2O–urea–DMF electrolyte before cycling is 0.05 μg mL−1. After 50 cycles and after 100 cycles, the concentrations of V-ions in the Na–H2O–urea–DMF electrolyte are 16.65 μg mL−1 and 20.12 μg mL−1, respectively. In 1 M Na2SO4 solution, the concentrations of V-ions are 0.08 μg mL−1, 60.68 μg mL−1 and 72.34 μg mL−1, respectively. Compared to 1 M Na2SO4 solution, the Na–H2O–urea–DMF electrolyte can obviously inhibit the dissolution of the electrode materials. Upon comparison of the V-ion concentrations in NaClO4 solution, Na–H2O–DMF, and Na–H2O–urea electrolyte of the NVP//NTP full cell after 50 cycles (Fig. S14†), it is found that the Na–H2O–urea–DMF electrolyte can suppress the dissolution of V-ions in the charge–discharge process. This result is consistent with the cycling performances of the NVP//NTP full cell in different electrolytes (Fig. S13†). Thus, it can be concluded that the NVP/C cathode is much more stable in the Na–H2O–urea–DMF electrolyte, which is beneficial for the long lifespan of the full cell. Similarly, as illustrated in Fig. S15,† the NTP anode in the Na–H2O–urea–DMF electrolyte displays high coulombic efficiency and good cycling stability relative to that in 17 M NaClO4 and 1 M Na2SO4 solution.

Question: What's the electrolyte?
Answer:  Na–H2O–urea–DMF
P. M. V. conceived the idea of the nanomesh-based cathodes and their development was supervised by S. P. Z. S. P. Z. developed the method for coating the nanomesh with MnO2 and its thermal activation and performed thermodynamic simulations and electrochemical testing. D. C. contributed to the development of the MnO2 coating, activation of the cathodes with Li citrate and electrochemical testing. D. C. also assisted in the in situ XRD experiments performed by F. Mattelaer in the group of C. Detavernier, University of Ghent. The manuscript was written by S. P. Z. and revised by P. M. V. All authors have given approval to the final version of the manuscript.

Question: What's the anode?
Answer: nanomesh-based
Chemical reactions during storage generate electrically insulating carbonate which elevates internal cell resistance and also alters the surface morphology. The electronic and ionic insulation of carbonate induces a sequence of chemical/electrochemical reaction behaviors. For instance, the transformed Lewis base surfaces can react with electrolytic species, generating detrimental species such as HF and gases. Therefore, extra cautions are required when preparing or handling LiNiO2-based materials before the battery assembly (Fig. 1). Herein, we evaluate the battery performance of the LiNiO2 cathode after storage in the dry box (humidity: ∼30%) and Ar glove box (the water level was ∼0.5 ppm) for two weeks. Two weeks would be a reasonable time frame between the synthesis of cathode powders and their processing into batteries in the actual manufacturing.

Question: What's the cathode?
Answer: LiNiO2
However, due to the slow kinetics of both HER at the cathode and UOR at the anode in urea–water electrolysis, electrocatalysts on the electrodes are necessary to speed up the reactions to achieve high energy efficiency. Traditional noble metal catalysts, such as Pt/C, RuO2, or IrO2, can effectively catalyze monolithic electrolysis, but their low abundance and high cost limit their wide application. Therefore, it is necessary to explore efficient non-noble metal electrocatalysts, such as transition metal compounds, transition metal oxides, macrocycles, nitrides, sulfides, phosphides, etc. Among these catalyst materials, the phosphides have been explored most recently, mainly due to their good conductivity and wettability, including MoP, CoP, FeP, and Ni2P. With regard to cost, abundance, catalytic activity, stability and applicable pH range, MoP has been shown to be a promising candidate.

Question: What's the cathode?
The UTCNF cathode was prepared via a simple and efficient ultrasonic-treatment strategy. In detail, a piece of pre-cleaned CNF (1 cm × 3 cm × 0.15 cm), thoroughly washed with acetone and water, was immersed in 3 M HCl. Next, the solution was transferred to an ultrasonic apparatus and ultrasonicated for 10 min. After the ultrasonic treatment, the CNF was rinsed with distilled water twice and dried at 60 °C to obtain the UTCNF. The mass loading of the cobalt/nickel composite hydroxide, obtained by comparison of the weight change between UTCNF and CNF, is ∼6.0 mg cm−2.

Question: What's the cathode?
Answer: UTCNF
Lithium–sulfur batteries have low material costs and high energy densities, which have attracted considerable research interest for application in next-generation energy-storage systems. However, the practical applications of Li–S batteries face challenges owing to their poor sulfur utilization, service lifetimes, and rate capability. Recently, great progress has been made in the design, synthesis, and application of micro/nanostructured metal sulfides to address obstacles facing Li–S batteries. This review aims to highlight valuable concepts from the latest reports. Major approaches to improve sulfur cathodes and strategies for preparing metal sulfide-based materials are first summarized with a particular focus on their main functions and useful properties. Then, the electrochemical activities of metal sulfides are classified and their applications in Li–S batteries are introduced to provide a fundamental understanding of the material interactions involved. In parallel, advancements in the use of interlayers, modification of separators, and protection of lithium anodes that involve metal sulfides are surveyed. Finally, special attention is paid to the general design principles, future prospects, and challenges facing metal sulfides for high-energy-density Li–S batteries.

Question: What's the cathode?
Answer: sulfur
The technology of engineering nanostructured materials is usually applied to create numerous active sites, which can significantly improve the electrochemical performance. Recently, the 2D morphology of nanosheet materials with high specific area has been proved to effectively accelerate the electrochemical kinetics between the active materials and the electrolytes, which are therefore supposed to be promising materials for energy storage. Unfortunately, the serious aggregation behavior in 2D materials, derived from the van der Waals forces among individual nanosheets, will decrease the exposed active sites, thus leading to poor conductivity. Carbon cloth (CC) has been known to be an inexpensive substrate/current collector capable of providing continuous pathways for the transport of electrons. Following the above-mentioned discussions, it would be reasonable to believe that an intriguing way of overcoming the above problems is the in situ growth of 2D nanosheet compounds on a flexibly conductive substrate to obtain a free-standing cathode, aiming at achieving good rate capability, high capacity, and energy density simultaneously.

Question: What's the cathode?
A carbon nanotube film was used as the oxygen cathode and Li foil with 0.5 mm thickness as the anode for LOBs. A glass fiber separator wetted with a 100 μL electrolyte composed of 1.0 M LiTFSI in TEGDME was employed to separate the cathode and anode. All assembled cells were measured on a LAND electrochemical testing system at 25 °C. The cycling test was conducted with the capacity limited at 1000 mA h g−1 at a current density of 300 mA g−1.

Question: What's the cathode?
Answer: oxygen
A carbon nanotube film was used as the oxygen cathode and Li foil with 0.5 mm thickness as the anode for LOBs. A glass fiber separator wetted with a 100 μL electrolyte composed of 1.0 M LiTFSI in TEGDME was employed to separate the cathode and anode. All assembled cells were measured on a LAND electrochemical testing system at 25 °C. The cycling test was conducted with the capacity limited at 1000 mA h g−1 at a current density of 300 mA g−1.

Question: What's the anode?
Answer: Li foil
Co-free Ni-rich cathode materials, particularly LiNiO2 and its doped analogs, face ongoing challenges as the need for commercialization rises. To address surface instability and its associated phenomena, a systematic and accurate understanding is highly required. In this work, we systematically studied the fragile surfaces of the LiNiO2-based cathode materials, with the goal of identifying how experimental conditions may influence characterization results. We presented the challenges in characterizing and analyzing the surface chemistry of LiNiO2-based materials using two comparative cathodes as a model platform, i.e., LiNiO2 versus Mg/Ti–LiNiO2. The surface lithium residuals are inevitable and highly dependent on various sample storage and handling conditions. Due to the highly reactive surfaces, we found that the sample preparation for electron microscopy and surface-sensitive X-ray analyses greatly influences the final observations, resulting in skewed surface chemistry analytical results. We also provided some recommendations regarding how to obtain representative characterization analyses. Using simple comparisons, we further illustrated the advantages of Mg/Ti dual dopants to enhance the surface structural resistance to many circumstances, while corroborating previously reported observations. However, we found that the surface of Mg/Ti–LiNiO2 material still encounters a series of problems caused by the fragile CEIs at elevated temperatures. Efforts should be devoted towards the development of highly stable CEIs either by cathode surface coating, doping, electrolyte modification or combining multiple strategies.

Question: What's the cathode?
Answer: Co-free Ni-rich
Co-free Ni-rich cathode materials, particularly LiNiO2 and its doped analogs, face ongoing challenges as the need for commercialization rises. To address surface instability and its associated phenomena, a systematic and accurate understanding is highly required. In this work, we systematically studied the fragile surfaces of the LiNiO2-based cathode materials, with the goal of identifying how experimental conditions may influence characterization results. We presented the challenges in characterizing and analyzing the surface chemistry of LiNiO2-based materials using two comparative cathodes as a model platform, i.e., LiNiO2 versus Mg/Ti–LiNiO2. The surface lithium residuals are inevitable and highly dependent on various sample storage and handling conditions. Due to the highly reactive surfaces, we found that the sample preparation for electron microscopy and surface-sensitive X-ray analyses greatly influences the final observations, resulting in skewed surface chemistry analytical results. We also provided some recommendations regarding how to obtain representative characterization analyses. Using simple comparisons, we further illustrated the advantages of Mg/Ti dual dopants to enhance the surface structural resistance to many circumstances, while corroborating previously reported observations. However, we found that the surface of Mg/Ti–LiNiO2 material still encounters a series of problems caused by the fragile CEIs at elevated temperatures. Efforts should be devoted towards the development of highly stable CEIs either by cathode surface coating, doping, electrolyte modification or combining multiple strategies.

Question: What's the cathode?
Answer: LiNiO2-based
In this paper, MoP and NiCo-LDH are used to synthesize a composite of MoP@NiCo-LDH, which is supported on nickel foam to form a bifunctional composite catalyst (abbreviated as MoP@NiCo-LDH/NF), as shown in Fig. 1. During the synthesis, different electrodeposition times are used to optimize the catalyst's performance toward both UOR and HER. Both instrumental characterization and electrochemical measurements confirm that the composition between MoP and NiCo-LDH as well as their electrodeposition onto the NF surface can increase the material's specific surface area and produce a synergetic effect toward high performance. To validate this bifunctional catalyst, a two-electrode electrolyser (MoP@NiCo-LDH/NF-20‖MoP@NiCo-LDH/NF-20) with this catalyst on both the anode and the cathode was designed and constructed, and the test results show that this catalyst has better catalytic performance than that of a Pt/C/NF‖IrO2/NF electrolyser, where noble metal materials (Pt and IrO2) are used as the catalysts.

Question: What's the cathode?
In this paper, MoP and NiCo-LDH are used to synthesize a composite of MoP@NiCo-LDH, which is supported on nickel foam to form a bifunctional composite catalyst (abbreviated as MoP@NiCo-LDH/NF), as shown in Fig. 1. During the synthesis, different electrodeposition times are used to optimize the catalyst's performance toward both UOR and HER. Both instrumental characterization and electrochemical measurements confirm that the composition between MoP and NiCo-LDH as well as their electrodeposition onto the NF surface can increase the material's specific surface area and produce a synergetic effect toward high performance. To validate this bifunctional catalyst, a two-electrode electrolyser (MoP@NiCo-LDH/NF-20‖MoP@NiCo-LDH/NF-20) with this catalyst on both the anode and the cathode was designed and constructed, and the test results show that this catalyst has better catalytic performance than that of a Pt/C/NF‖IrO2/NF electrolyser, where noble metal materials (Pt and IrO2) are used as the catalysts.

Question: What's the anode?
Fig. S3d† and 4d display cyclic voltammogram (CV) curves obtained using the S-C(PAN) anode with bare LMO and LMO-30 min in the potential range of 1.0–3.2 V at a scan rate of 0.1 mV s−1, respectively. One peak is observed in both positive and negative scans in both samples. For the LMO-30 min cathode, a more pronounced peak appearing at 2.63 V in the first positive scan is observed and the peak is shifted to 2.45 V in the subsequent cycles. The peak of the negative scan appears at 1.77 V as depicted in Fig. 4d, which shows that PVDF@LGLZNO does not practically involve in the redox reactions of the tested voltage range, thus the composite coating must be stable and did not contribute to the capacity. The large polarization between the peaks in the first and following cycles is due to SPAN activation energy and the SEI formation. This means that more energy is needed to dissociate the sulfur atom from the pyridine-derivative, which is usually termed as the unique activation process of sulfurized polyacrylonitrile.

Question: What's the cathode?
Answer: LMO
Fig. S3d† and 4d display cyclic voltammogram (CV) curves obtained using the S-C(PAN) anode with bare LMO and LMO-30 min in the potential range of 1.0–3.2 V at a scan rate of 0.1 mV s−1, respectively. One peak is observed in both positive and negative scans in both samples. For the LMO-30 min cathode, a more pronounced peak appearing at 2.63 V in the first positive scan is observed and the peak is shifted to 2.45 V in the subsequent cycles. The peak of the negative scan appears at 1.77 V as depicted in Fig. 4d, which shows that PVDF@LGLZNO does not practically involve in the redox reactions of the tested voltage range, thus the composite coating must be stable and did not contribute to the capacity. The large polarization between the peaks in the first and following cycles is due to SPAN activation energy and the SEI formation. This means that more energy is needed to dissociate the sulfur atom from the pyridine-derivative, which is usually termed as the unique activation process of sulfurized polyacrylonitrile.

Question: What's the anode?
Answer: S-C(PAN)
Fig. 3 shows the electrochemical performances of a half-cell in a three-electrode system and a NVP//NTP full cell. As shown in Fig. 3a and b, the NVP half-cell exhibits a pair of redox peaks with good symmetry at 0.68 V and 0.42 V vs. Ag/AgCl, which can be ascribed to the reversible conversion of the V3+/V4+ couple, corresponding to the reversible extraction/insertion of Na+ in the NVP electrode. The half-cell delivers a specific charge and discharge capacity of 110 mA h g−1 and 96 mA h g−1 in the first cycle, and exhibits good reversibility for the first time. The irreversible charge capacity mainly resulted from the dissolution of the V-ions until the appearance of O2 evolution which was recorded in CV curves. For NTP, a pair of Ti4+/Ti3+ redox peaks at −0.55 V and −0.82 V vs. Ag/AgCl can be found in the CV curves. As seen in Fig. 3c, the CV curves show that the hydrogen evolution reaction still does not occur when the potential is −1.1 V vs. Ag/AgCl, which suggests that the Na–H2O–urea–DMF electrolyte can inhibit the side reaction well. As shown in Fig. 3d, the NTP in the Na–H2O–urea–DMF electrolyte delivers a pristine discharge capacity of 118 mA h g−1, concurrently exhibiting a perfect platform and good reversibility, which is better than that of a NTP anode with cationic doping. As shown in Fig. S10 and S11,† the NTP anode exhibits an impressive cycling stability in a conventional non-aqueous electrolyte. However, the coulombic efficiency and cycling performance of the NVP cathode at 2C in a conventional non-aqueous electrolyte are poor due to the dissolution of V-ions and change of structure.

Question: What's the cathode?
Answer: NVP