eScience

Self-rechargeable energizers for sustainability

Ling JinKiong, Kunwar Ria, Li Linlin, Peng Shengjie, Misnon Izan Izwan, Ab Rahim Mohd Hasbi, Yang Chun-Chen, Jose Rajan

2022, 2(4): 347-364. doi: 10.1016/j.esci.2022.07.002

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Abstract:
Electrical energy generation and storage have always been complementary to each other but are often disconnected in practical electrical appliances. Recently, efforts to combine both energy generation and storage into self-powered energizers have demonstrated promising power sources for wearable and implantable electronics. In line with these efforts, achieving self-rechargeability in energy storage from ambient energy is envisioned as a tertiary energy storage (3rd-ES) phenomenon. This review examines a few of the possible 3rd-ES capable of harvesting ambient energy (photo-, thermo-, piezo-, tribo-, and bio-electrochemical energizers), focusing also on the devices' sustainability. The self-rechargeability mechanisms of these devices, which function through modifications of the energizers' constituents, are analyzed, and designs for wearable electronics are also reviewed. The challenges for self-rechargeable energizers and avenues for further electrochemical performance enhancement are discussed. This article serves as a one-stop source of information on self-rechargeable energizers, which are anticipated to drive the revolution in 3rd-ES technologies.

Additive manufacturing (3D printing) of electrically conductive polymers and polymer nanocomposites and their applications

Ryan Kirstie R., Down Michael P., Hurst Nicholas J., Keefe Edmund M., Banks Craig E.

2022, 2(4): 365-381. doi: 10.1016/j.esci.2022.07.003

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Abstract:
Additive manufacturing, or three-dimensional (3D) printing, offers a unique solution for fabricating complex geometries with high tolerances. Currently, many commercial additive manufacturing machines focus on the printing of polymers with limited functionalities. However, conductive polymers (CPs) can be processed to enable the additive manufacturing of conductive, low-density, and low-cost parts for a myriad of applications. This review summarizes the relevant achievements in the additive manufacturing of conductive polymers (CPs) and conductive polymer nanocomposites, with a discussion of the advantages and limitations of processing and printing these materials compared with alternative traditional manufacturing methods and their properties. Finally, the prospective applications of these additive manufacturing printed conductive materials are explored.

ITO@TiO₂ nanoarray: An efficient and robust nitrite reduction reaction electrocatalyst toward NH₃ production under ambient conditions

Li Shaoxiong, Liang Jie, Wei Peipei, Liu Qian, Xie Lisi, Luo Yonglan, Sun Xuping

2022, 2(4): 382-388. doi: 10.1016/j.esci.2022.04.008

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Abstract:
Ambient electrochemical nitrite (NO₂^-) reduction is viewed as an effective and sustainable approach for simultaneously removing NO₂^- and producing ammonia (NH₃). However, the complex multi-electron transfer steps involved in the NO₂^- reduction reaction (NO₂^-RR) lead to sluggish kinetics and low product selectivity toward NH₃, underscoring the need for NH₃ synthesis electrocatalysts with high activity and durability. Herein, we report amorphous indium–tin oxide sputtered on a TiO₂ nanobelt array on a Ti plate (ITO@TiO₂/TP) as a 3D NH₃-producing catalyst for the NO₂^-. In 0.5 M LiClO₄ with 0.1 M NO₂^-, it shows greatly boosted NO₂^-RR activity toward NH₃ production, with excellent selectivity, achieving a large NH₃ yield of 411.3 μmol h^-1 cm^-2 and a high Faradaic efficiency of 82.6%. It also shows high durability for continuous electrolysis. A Zn-NO₂^- battery with ITO@TiO₂/TP cathode offers an NH₃ yield of 23.1 μmol h^-1 cm^-2 and a peak power density of 1.22 mW cm^-2.

Tailoring the adsorption behavior of superoxide intermediates on nickel carbide enables high-rate Li–O₂ batteries

Liu Yun, Cai Jinyan, Zhou Jianbin, Zang Yipeng, Zheng Xusheng, Zhu Zixuan, Liu Bo, Wang Gongming, Qian Yitai

2022, 2(4): 389-398. doi: 10.1016/j.esci.2022.06.002

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Abstract:
Probing the relationship between the adsorption of superoxide species and the kinetics of Li–O₂ chemistry is critical for designing superior oxygen electrodes for the Li–O₂ battery, yet the modulation essence, especially at the atomic level, remains little understood. Herein, we reveal that the adsorption behaviors of superoxide species can be effectively regulated via a core-induced interfacial charge interaction, and we find that moderate adsorption strength can enable superior rate capability in a Li–O₂ battery. More importantly, operando X-ray absorption near-edge structure and surface-enhanced Raman spectroscopy provide tools to monitor in situ the evolution of the superoxide intermediates and the electronic states of the catalyst's metal sites during the discharge and charge processes, and correlate these with the surface adsorption states. The concept of tuning adsorption behavior through interfacial charge engineering could open up new opportunities to further advance the development of the Li–O₂ battery and beyond.

Single atomic cobalt electrocatalyst for efficient oxygen reduction reaction

Rao Peng, Wu Daoxiong, Wang Tian-Jiao, Li Jing, Deng Peilin, Chen Qi, Shen Yijun, Chen Yu, Tian Xinlong

2022, 2(4): 399-404. doi: 10.1016/j.esci.2022.05.004

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Abstract:
Robust oxygen reduction reaction (ORR) catalysts are essential for energy storage and conversion devices, but their development remains challenging. Herein, we design a single-atom catalyst featuring isolated Co anchored on nitrogen-doped carbon (Co-SAC/NC) via a highly efficient "plasma-bombing" strategy. With a high loading (up to 2.5 wt%), the well-dispersed single Co atoms in Co-SAC/NC give it robust ORR performance in an alkaline medium. It also demonstrates excellent battery performance when implemented as the air-cathode catalyst in a zinc-air battery (ZAB). Theoretical calculations reveal that the Co–N₄ moiety experiences an "extraction/recovery" structural evolution during the ORR process, and the reaction's rate-determining step is the formation of OOH^* (reaction intermediate). This work provides a new strategy for designing robust ORR catalysts for high-performance ZABs and other energy-conversion devices.

Surface strain-enhanced MoS₂ as a high-performance cathode catalyst for lithium–sulfur batteries

Zhang Chao Yue, Zhang Chaoqi, Pan Jiang Long, Sun Guo Wen, Shi Zude, Li Canhuang, Chang Xingqi, Sun Geng Zhi, Zhou Jin Yuan, Cabot Andreu

2022, 2(4): 405-415. doi: 10.1016/j.esci.2022.07.001

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Abstract:
Lithium–sulfur batteries (LSBs) are one of the main candidates for the next generation of energy storage systems. To improve the performance of LSBs, we herein propose the use of strained MoS₂ (s-MoS₂) as a catalytically active sulfur host. The introduction of strain in the MoS₂ surface, which alters its atomic positions and expands the S–Mo–S angle, shifts the d-band center closer to the Fermi level and provides the surface with abundant and highly active catalytic sites; these enhance the catalyst's ability to adsorb lithium polysulfides (LiPS), accelerating its catalytic conversion and promoting lithium-ion transferability. Strain is generated through the synthesis of core–shell nanoparticles, using different metal sulfides as strain-inducing cores. s-MoS₂ nanoparticles are supported on carbon nanofibers (CNF/s-MoS₂), and the resulting electrodes are characterized by capacities of 1290 and 657 mAh g⁻¹ at 0.2 and 5 C, respectively, with a 0.05% capacity decay rate per cycle at 8 C during 700 cycles. Overall, this work not only provides an ingenious and effective strategy to regulate LiPS adsorption and conversion through strain engineering, but also indicates a path toward the application of strain engineering in other energy storage and conversion fields.

Magic hybrid structure as multifunctional electrocatalyst surpassing benchmark Pt/C enables practical hydrazine fuel cell integrated with energy-saving H₂ production

Li Ziyun, Wang Wentao, Qian Qizhu, Zhu Yin, Feng Yafei, Zhang Yangyang, Zhang Huaikun, Cheng Mingyu, Zhang Genqiang

2022, 2(4): 416-427. doi: 10.1016/j.esci.2022.06.004

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Abstract:
A hybrid catalyst structure can provide abundant active sites and tailored electronic properties, but the major challenge lies in achieving delicate control over its composition and architecture to improve the catalytic activity toward different electrochemical reactions simultaneously. Herein, we present the rational design of a magic hybrid structure with low Pt loading (5.90 wt%), composed of CoPt₃ and CoPt nanoparticles supported on N-doped carbon (CoPt₃/CoPt⊂P_LNC). Importantly, it shows superior multifunctional catalytic activity in alkaline conditions, requiring a low overpotential of 341 and 20 mV to achieve 10 mA cm⁻² for the hydrazine oxidation reaction (HzOR)/hydrogen evolution reaction (HER), respectively, and it delivers a half-wave potential of 0.847 V for the oxygen reduction reaction (ORR). Theoretical calculations reveal that the metal–carbon hybrid modulates kinetic behavior and induces electron redistribution, achieving the energetic requirements for multiple electrocatalysis. We demonstrate sustainable H₂ production utilizing solely the CoPt₃/CoPt⊂P_LNC catalyst, without external electric power input, suggesting its inspiring practical utility.

Porous fixed-bed photoreactor for boosting C–C coupling in photocatalytic CO₂ reduction

Bai Shengjie, Qiu Haoran, Song Mengmeng, He Guiwei, Wang Feng, Liu Ya, Guo Liejin

2022, 2(4): 428-437. doi: 10.1016/j.esci.2022.06.006

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Solar-driven CO₂ conversion to chemical fuels in an aqueous solution is restricted not only by photocatalysts but also by mass transfer. Here, a regulatable three-phase interface on a porous fixed-bed is constructed for efficient C–C coupling in photocatalytic CO₂ reduction. The photocatalytic results show that ~90% selectivity towards C2+ products is obtained by a Cu/Cd_0.5Zn_0.5S photocatalyst, with a yield of 6.54 μmol/h (an irradiation area of 0.785 cm²), while only 0.94 μmol/h (an irradiation area of 19.625 cm²) is achieved with a commonly used suspension photocatalytic reactor. We find that under the same CO₂ feed rate, the local CO₂ concentration in this porous fixed-bed photoreactor is obviously higher than in the suspension photoreactor. The larger local CO₂ coverage derived from a higher CO₂ supply and aggregation enhances the C–C coupling, thereby generating more C2+. Even an observable three-phase interface on the porous fixed-bed can be regulated by adjusting the CO₂ supply, for which the optimal gas inlet rate is 5–10 sccm.

A potential-driven switch of activity promotion mode for the oxygen evolution reaction at Co₃O₄/NiO_xH_y interface

Wang Wang, Wang Zixu, Hu Youcheng, Liu Yucheng, Chen Shengli

2022, 2(4): 438-444. doi: 10.1016/j.esci.2022.04.004

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Abstract:
Co₃O₄ spinel oxides have manifested promising activity toward the oxygen evolution reaction (OER) through effective modifications. For them to become top electrocatalysts, however, accurate accounts of the catalytic kinetics are essential to gain a deep understanding of the activity promotion mechanisms. Herein, we use a newly proposed kinetic model based on energetic span as the rate-determining term for the electrocatalytic reaction to throw light on the promotion mechanism of Co₃O₄ interfaced with nickel hydroxides (NiO_xH_y) for the OER. We find that depending on the electrode potential, the OER kinetics at the designed interface between Co₃O₄ and NiO_xH_y are boosted in entirely different ways. As a result, the OER can occur at a lower onset potential as well as a low Tafel slope. This work emphasizes the benefit of using rational theoretical models for electrocatalyst design.

Improving NiN_X and pyridinic N active sites with space-confined pyrolysis for effective CO₂ electroreduction

Zhu Zhaozhao, Li Zhao, Wang Junjie, Li Rong, Chen Haiyuan, Li Yulan, Chen Jun Song, Wu Rui, Wei Zidong

2022, 2(4): 445-452. doi: 10.1016/j.esci.2022.05.002

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Abstract:
Even though various nickel–nitrogen–carbon (Ni-N-C) combinations are prospective low-cost catalysts for the CO₂ electroreduction reaction (CO₂RR), which is one avenue for attaining carbon neutrality, the detailed role of different N species has hardly been investigated. Here, we report a hollow porous N-doped carbon nanofiber with NiN_X-pyridinic N active species (denoted as h-Ni-N-C) developed using a facile electrospinning and SiO₂ space-confined pyrolysis strategy. The NiN_X-pyridinic N species are facilely generated during the pyrolysis process, giving rise to enhanced activity and selectivity for the CO₂RR. The optimized h-Ni-N-C exhibits a high CO Faradaic efficiency of 91.3% and a large current density of −15.1 mA cm⁻² at −0.75 V versus reversible hydrogen electrode in an H-cell. Density functional theory (DFT) results show that NiN₄-pyridinic N species demonstrate a lower free energy for the catalyst's rate-determining step than isolated NiN₄ and pyridinic N species, without affecting the desorption of CO* intermediate.

2022 Vol. 2, No. 4