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Zhang, Yi; Zhang, Chenglin; Fu, Qun; Zhao, Huaping; Lei, Yong;
Modified polydopamine derivatives as high-performance organic anodes for potassium-ion batteries. - In: Sustainable energy & fuels, ISSN 2398-4902, Bd. 6 (2022), 15, S. 3527-3535

Polydopamine (PDA) as a carbon source and a versatile coating material has been widely studied in rechargeable battery electrodes. However, it is rare to directly utilize PDA as an organic anode for ion storage, especially in potassium-ion batteries (PIBs). In this work, modified PDA (MPDA-350) with a porous structure is synthesized by collective methods of template-assisted and low-temperature pyrolysis, which endows PDA with large ion diffusion tunnels and increased active sites for K+ ion storage. Moreover, contrast experiments demonstrate that the annealing process with an appropriate temperature can increase the content and activity of electroactive groups in MPDA-350. The prepared MPDA-350 is first applied to PIBs that deliver high reversible capacity (384.9 mA h g^-1 at 100 mA g^-1) and very stable cyclability (99.94% capacity retention after 500 cycles). This work provides a new insight for the expansion of high-performance organic anodes for PIBs.
Xu, Bowen; Zhang, Da; Chang, Shilei; Hou, Minjie; Peng, Chao; Xue, Dongfeng; Yang, Bin; Lei, Yong; Liang, Feng;
Fabrication of long-life quasi-solid-state Na-CO2 battery by formation of Na2C2O4 discharge product. - In: Cell reports, ISSN 2666-3864, Bd. 3 (2022), 7, 100973, S. 1-15

Rechargeable Na-CO2 batteries are promising energy-storage devices due to their high energy density, environmental friendliness, and cost effectiveness. However, the insulating nature and irreversibility of the Na2CO3 discharge product cause large polarization and poor cyclicity. Here, we report a reversible quasi-solid-state Na-CO2 battery that is constructed by the synergistic action of a Co-encapsulated N-doped carbon framework catalyst and gel electrolyte to ensure the formation of a highly reversible Na2C2O4 discharge product. Experiments and density functional theory calculations indicate that the electron-agglomeration effect of Co nanoparticles enhances CO2 adsorption and lowers energy barrier, as well as promotes Na2C2O4 generation. A gel electrolyte containing an imidazole organic cation is used to inhibit the decomposition of the thermodynamically unstable Na2C2O4. The fabricated Na-CO2 battery exhibits a high discharge capacity of 3,094 mAh g^-1, a high-rate performance of 1,777 mAh g^-1 at a current density of 0.5 mA cm^-2, and excellent cycling performance of 366 cycles (2,200 h).
Yang, Guowei; Yan, Chengzhan; Hu, Ping; Fu, Qun; Zhao, Huaping; Lei, Yong;
Synthesis of CoSe2 reinforced nitrogen-doped carbon composites as advanced anodes for potassium-ion batteries. - In: Inorganic chemistry frontiers, ISSN 2052-1553, Bd. 9 (2022), 15, S. 3719-3727

Potassium-ion batteries (PIBs) are considered potential candidates for large-scale energy storage applications with cost superiority. However, the development of PIBs is severely restricted by the sluggish electrochemical kinetics and severe volume expansion of anode materials. Herein, CoSe2 reinforced nitrogen-doped carbon composites (CoSe2C) are synthesized via a simple solution-based etching-coating method and further studied as high-performance anodes for PIBs. Electrochemical characterization studies indicate that the potassium storage performance of CoSe2@C composite anodes relies on the initial mass ratio of CoSe2 nanosheets and carbon precursors (that is dopamine hydrochloride) during the synthesis process. In the case of the mass ratio of CoSe2 nanosheets and dopamine hydrochloride being 1 : 1, the as-obtained CoSe2@C-1 : 1 anode exhibits a high reversible capacity (366.1 mA h g^-1 at 0.1 A g^-1 after 100 cycles), an excellent long-cycle stability (237.6 mA h g^-1 at 1.0 A g^-1 after 1000 cycles), and a good rate capability (281.5 mA h g^-1 at 5.0 A g^-1). The optimum performance of CoSe2@C-1 : 1 as a PIB anode in terms of cycling stability and kinetics is attributed to the uniform distribution of CoSe2 nanoparticles inside the carbon matrix.
Segev, Gideon; Kibsgaard, Jakob; Hahn, Christopher; Xu, Zhichuan J.; Cheng, Wen-Hui (Sophia); Deutsch, Todd G.; Xiang, Chengxiang; Zhang, Jenny Z.; Hammarström, Leif; Nocera, Daniel G.; Weber, Adam Z.; Agbo, Peter; Hisatomi, Takashi; Osterloh, Frank E.; Domen, Kazunari; Abdi, Fatwa F.; Haussener, Sophia; Miller, Daniel J.; Ardo, Shane; McIntyre, Paul C.; Hannappel, Thomas; Hu, Shu; Atwater, Harry; Gregoire, John M.; Ertem, Mehmed Z.; Sharp, Ian; Choi, Kyoung-Shin; Lee, Jae Sung; Ishitani, Osamu; Ager, Joel W.; Prabhakar, Rajiv Ramanujam; Bell, Alexis T.; Boettcher, Shannon W.; Vincent, Kylie; Takanabe, Kazuhiro; Artero, Vincent; Napier, Ryan; Roldán Cuenya, Beatriz; Koper, Marc T. M.; Van De Krol, Roel; Houle, Frances;
The 2022 solar fuels roadmap. - In: Journal of physics, ISSN 1361-6463, Bd. 55 (2022), 32, 323003, S. 1-52

Renewable fuel generation is essential for a low carbon footprint economy. Thus, over the last five decades, a significant effort has been dedicated towards increasing the performance of solar fuels generating devices. Specifically, the solar to hydrogen efficiency of photoelectrochemical cells has progressed steadily towards its fundamental limit, and the faradaic efficiency towards valuable products in CO2 reduction systems has increased dramatically. However, there are still numerous scientific and engineering challenges that must be overcame in order to turn solar fuels into a viable technology. At the electrode and device level, the conversion efficiency, stability and products selectivity must be increased significantly. Meanwhile, these performance metrics must be maintained when scaling up devices and systems while maintaining an acceptable cost and carbon footprint. This roadmap surveys different aspects of this endeavor: system benchmarking, device scaling, various approaches for photoelectrodes design, materials discovery, and catalysis. Each of the sections in the roadmap focuses on a single topic, discussing the state of the art, the key challenges and advancements required to meet them. The roadmap can be used as a guide for researchers and funding agencies highlighting the most pressing needs of the field.
Hähnlein, Bernd; Sagar, Neha; Honig, Hauke; Krischok, Stefan; Tonisch, Katja;
Anisotropy of the ΔE effect in Ni-based magnetoelectric cantilevers: a finite element method analysis. - In: Sensors, ISSN 1424-8220, Bd. 22 (2022), 13, 4958, S. 1-16

In recent investigations of magnetoelectric sensors based on microelectromechanical cantilevers made of TiN/AlN/Ni, a complex eigenfrequency behavior arising from the anisotropic ΔE effect was demonstrated. Within this work, a FEM simulation model based on this material system is presented to allow an investigation of the vibrational properties of cantilever-based sensors derived from magnetocrystalline anisotropy while avoiding other anisotropic contributions. Using the magnetocrystalline ΔE effect, a magnetic hardening of Nickel is demonstrated for the (110) as well as the (111) orientation. The sensitivity is extracted from the field-dependent eigenfrequency curves. It is found, that the transitions of the individual magnetic domain states in the magnetization process are the dominant influencing factor on the sensitivity for all crystal orientations. It is shown, that Nickel layers in the sensor aligned along the medium or hard axis yield a higher sensitivity than layers along the easy axis. The peak sensitivity was determined to 41.3 T−1 for (110) in-plane-oriented Nickel at a magnetic bias flux of 1.78 mT. The results achieved by FEM simulations are compared to the results calculated by the Euler-Bernoulli theory.
Emminger, Carola; Espinoza, Shirly; Richter, Steffen; Rebarz, Mateusz; Herrfurth, Oliver; Zahradník, Martin; Schmidt-Grund, Rüdiger; Andreasson, Jakob; Zollner, Stefan;
Coherent acoustic phonon oscillations and transient critical point parameters of Ge from femtosecond pump-probe ellipsometry. - In: Physica status solidi, ISSN 1862-6270, Bd. 16 (2022), 7, 2200058, S. 1-7

Herein, the complex pseudodielectric function of Ge and Si from femtosecond pump-probe spectroscopic ellipsometry with 267, 400, and 800 nm pump-pulse wavelengths is analyzed by fitting analytical lineshapes to the second derivatives of the pseudodielectric function with respect to energy. This yields the critical point parameters (threshold energy, lifetime broadening, amplitude, and excitonic phase angle) of E 1 and E 1 + Δ 1 in Ge and E 1 in Si as functions of delay time. Coherent longitudinal acoustic phonon oscillations with a period of about 11 ps are observed in the transient critical point parameters of Ge. From the amplitude of these oscillations, the laser-induced strain is found to be on the order of 0.03% for Ge measured with the 800 nm pump pulse, which is in reasonable agreement with the strain calculated from theory.
Mathew, Sobin; Lebedev, Sergey P.; Lebedev, A. A.; Hähnlein, Bernd; Stauffenberg, Jaqueline; Manske, Eberhard; Pezoldt, Jörg;
Silicon carbide - graphene nano-gratings on 4H and 6H semi-insulating SiC. - In: Materials science forum, ISSN 1662-9752, Bd. 1062 (2022), S. 170-174

A technical methodology of fabrication of hierarchically scaled multitude graphene nanogratings with varying pitches ranging from the micrometer down to sub 40 nm scale combined with sub 10 nm step heights on 4H and 6H semi-insulating SiC for length scale measurements is proposed. The nanogratings were fabricated using electron-beam lithography combined with dry etching of graphene, incorporating a standard semiconductor processing technology. A scientific evaluation of critical dimension, etching step heights, and surface characterization of graphene nanograting on both polytypes were compared and evaluated.
Yang, Xiecheng; Peng, Chao; Hou, Minjie; Zhang, Da; Yang, Bin; Xue, Dongfeng; Lei, Yong; Liang, Feng;
Rational design of electrolyte solvation structures for modulating 2e-/4e- transfer in sodium-air batteries. - In: Advanced functional materials, ISSN 1616-3028, Bd. 32 (2022), 23, 2201258, S. 1-11

In sodium-air batteries (SABs), achieving the regulation of the electron transfer number during oxygen reduction reactions (ORRs) in the same electrolyte system remains a significant challenge. In this work, a promising strategy is proposed to dynamically modulate 2e-/4e- transfer in ORRs by regulating the electrolyte structures to realize the different performances of SABs. The 4e- ORR can be realized by decreasing the electrolyte concentration. The solvation sheath of Na+ at dilute concentrations consists mainly of water molecules that hinder the access of Na+ to the cathode surface due to the high solvation energies indicated by theoretical calculations, thereby impeding the 2e- reaction. In contrast, excess free water can easily access the cathode surface and trigger the 4e- ORR. The solvation energies of Na+ can be remarkably reduced by increasing the electrolyte concentration, forming a water-in-salt unit, in which the Na+ mainly coordinates with the bis(fluorosulfonyl)imide anion and can be easily released from the solvation sheath. Hence, the 2e- ORR is significantly promoted and becomes the dominant reaction. The SAB based on the 2e- reaction exhibits excellent energy density (15980 Wh kg-1) and good cycle performance (300 times), and the 4e- reaction exhibits excellent power density (12.09 mW cm-2).
Zhang, Yi; Sha, Mo; Fu, Qun; Zhao, Huaping; Lei, Yong;
An overview of metal-organic frameworks-derived carbon as anode materials for sodium- and potassium-ion batteries. - In: Materials Today Sustainability, ISSN 2589-2347, Bd. 18 (2022), 100156

With the decreasing abundance of lithium and the increasing cost of lithium-ion batteries (LIBs), exploring alternative metal-ion batteries has been a hotspot in the energy storage research area. Among next-generation batteries, sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) have been considered as competitive alternatives to LIBs due to the earth abundance of sodium and potassium. Metal-organic frameworks (MOFs)-derived carbon materials with high porosity, unique architectures, and abundant heteroatoms have been demonstrated as promising anode materials in SIBs and PIBs with high capacity and long cycling stability due to the adsorption energy storage mechanism. In this review, we highlight the advantages of carbon materials derived from MOFs as anode materials in SIBs and PIBs. In addition, the typical works and recent achievements are also introduced. Finally, the challenges and perspectives for further developing MOFs-derived carbon anode materials for SIBs and PIBs are also discussed.
Rothe, Karl; Néel, Nicolas; Bocquet, Marie-Laure; Kröger, Jörg;
Quantifying force and energy in single-molecule metalation. - In: Journal of the American Chemical Society, ISSN 1520-5126, Bd. 144 (2022), 16, S. 7054-7057

An atomic force microscope is used to determine the attractive interaction at the verge of adding a Ag atom from the probe to a single free-base phthalocyanine molecule adsorbed on Ag(111). The experimentally extracted energy for the spontaneous atom transfer can be compared to the energy profile determined by density functional theory using the nudged-elastic-band method at a defined probe-sample distance.