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What is known and objective: Metformin has been suggested to confer anticancer efficacy. However, it remains uncertain whether additional use of metformin could improve survival of women with breast cancer. We performed a meta‐analysis of randomized controlled trials (RCTs) to evaluate the influence of metformin on survival outcome in women with breast cancer. Methods: Relevant RCTs were obtained by search of PubMed, Embase and Cochrane's Library databases from inception to 15 May 2021. A random‐effects model incorporating the potential publication bias was used to pool the results. Results and discussion: Five phase II RCTs including 396 non‐diabetic women with breast cancer were included in the meta‐analysis. Pooled results showed that additional use of metformin was not associated with improved progression‐free survival (PFS, hazard ratio [HR]: 1.00, 95% confidence interval [CI]: 0.70 to 1.43, p = 0.98; I2 = 32%) or overall survival (OS, HR: 1.00, 95% CI: 0.71 to 1.39, p = 0.98; I2 = 0%). Sensitivity analysis by excluding one study at a time showed consistent results (HR for PFS: 0.91 to 1.14, p all >0.05; HR for OS: 0.88 to 1.21, P all >0.05). What is new and conclusion: Current evidence from phase II clinical trials does not support that additional use of metformin could improve the survival outcome in women with breast cancer. [ABSTRACT FROM AUTHOR]

Lithium‐carbon dioxide (Li‐CO2) batteries are considered as a most auspicious energy storage systems owing to their high capacity and the ability of capturing CO2. However, there are still some critical issues needed to be addressed before their practical application, such as high charge potential and poor cyclability. Herein, oxygen vacancy‐enriched TiO2 nanoparticles grown in situ on Ti3C2Tx MXene (OV‐TiO2/MXene) are synthesized as catalysts for Li‐CO2 batteries by facile one‐step ethanol heat treatment of the MXene nanosheets. The thermodynamically metastable Ti atom on the surface of MXenes serves as nucleating sites, which play a critical role in generating the relatively stable vacancy‐rich TiO2 nanoparticles. The spontaneously generated oxygen vacancies can enhance CO2 adsorption, which is beneficial to CO2 involved electrode reactions. The Li‐CO2 batteries with OV‐TiO2/MXene electrodes deliver noteworthily reduced charge voltage of 3.37 V at 100 mA g−1, and a superb cycling performance of 158 cycles. This work highlights the significant role of oxygen vacancies in activating CO2 in Li‐CO2 batteries, instrumental to the development of high‐performance electrocatalysts for Li‐CO2 batteries and beyond. [ABSTRACT FROM AUTHOR]

The inferior reversibility of the formation/decomposition of the lithium peroxide (Li2O2) and its insolubility and insulation features result in poor energy efficiency and limited durability of state-of-the-art Li–O2 batteries. Herein, we elaborately designed sisal-like CoSe2 nanowires enriched with Se vacancies (VSe-CoSe2) anchored on a scaffold of magnetron-sputtered N-doped carbon cloth (N-CC) to address the above challenges. The synergistic coupling of vacancy regulation with interfacial interaction can be used to tune the ability to adsorb active oxygen and intermediate species and enhance the interfacial electron transfer during oxygen redox reactions. Experimental results demonstrate that the VSe-CoSe2@N-CC-based Li–O2 battery demonstrates a substantially decreased overpotential (∼0.56 V) and extraordinary durability (over 955 h). This work indicates that the synergistic coupling of vacancy modulation and interface interaction is a promising strategy for effectively enhancing the comprehensive performance of Li–O2 batteries, which provide prospective insights into the exploration of next-generation highly efficient metal–air batteries. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) carbon aerogels with well-defined structures, e.g. high specific surface area (SSA), appropriate pore size distribution, good electrical conductivity and ideal building blocks, have been regarded as promising electrode materials or substrates for incorporation with pseudocapacitive materials for energy storage and conversion applications. Herein, we report a simple and scalable sonochemical method followed by a chemical activation process to transform bacterial cellulose-derived carbon nanofiber aerogels (CNFAs) into 3D graphene nanoribbon aerogels (GNRAs) for supercapacitors. Benefiting from a high SSA, reasonable pore size distribution and good conductivity, the GNRA electrode demonstrates a long cyclability, good rate capability and high charge storage performance for supercapacitors, yielding more than 1.5 times (three-electrode cell) and 2.6 times (two-electrode cell) the gravimetric capacitance of the CNFA electrode. In addition, a hybrid Ni–Co layered double hydroxides (LDHs)@GNRAs electrode achieves an impressive gravimetric capacitance of 968 F g−1 (based on the mass of the active material) at a current density of 1 A g−1. Moreover, an asymmetric supercapacitor device with a remarkable energy density of 29.87 Wh kg−1, wide working voltage windows of 1.6 V and good cycling stability (63.5% retention after 10 000 cycles) is achieved by using the GNRA as an anode and the Ni–Co LDHs@GNRAs as a cathode. [ABSTRACT FROM AUTHOR]

Integrating energy storage technologies with clean carbon dioxide (CO2) recycling is considered to be a promising solution to alleviate global warming caused by CO2 emission and meet the ever-increasing demand for electrical energy supplies. Recently, a rechargeable aprotic lithium–CO2 (Li–CO2) electrochemical system has been proposed as a new strategy for both energy storage and CO2 capture. However, the study of such a system remains preliminary, and its development still faces huge challenges such as low energy efficiency and electrolyte decomposition caused by a large charge overpotential, which are primarily attributed to the sluggish kinetics of the CO2 activation reaction in Li–CO2 batteries. Therefore, the reasonable design and fabrication of catalysts with excellent catalytic activity and high stability remain a formidable challenge to develop practical Li–CO2 batteries. In this review, based on the introduction of the structure and fundamental electrochemistry of Li–CO2 batteries, we provide an up-to-date and comprehensive review on state-of-the-art design strategies toward highly active catalytic materials and cathode structures for Li–CO2 batteries, inspiring research interests and concerns to this emerging energy storage system and promoting its practical application for future advances in this field. [ABSTRACT FROM AUTHOR]

In this work, a novel 2D CuCo 2 S 4 (CCS) nanosheets with spinel type structure is fabricated and used as the cathode catalyst for rechargeable Li-O 2 battery. The characteristic 2D nanosheets structure with exposure of special (113), (004), and (044) crystal faces provide sufficient active sites for ORR and OER, which promote the rate capability immensely as well as improve discharge capacity and cycle life of the battery. Specifically, Li-O 2 batteries with CCS electrodes show excellent cycle stability of more than 176 cycles at limiting capacity 500 mA h g−1 and superior rate performance (2254 mA h g−1 at 2000 mA g−1). For comparison, nanostructures of CuS and Co 3 S 4 have been synthesized employing the similar process used for CCS. When compared to conventional carbon material (Super P) and these two binary metal sulfides, CCS NSs provided the highest catalytic activities at the same mass loading. Which can be attributed to the introduction of copper in the Co 3 S 4 lattice offers the oxygen evolution and kinetics by enhancing Cu2+ sites and also by providing a high-active high-spin stat of octahedral Co3+ for ORR and OER catalysis. • The two-dimensional CuCo 2 S 4 nano-sheet synthesized via simple hydrothermal method effectively promoted the formation and decomposition of Li 2 O 2. • The CuCo 2 S 4 electrode exhibits a discharge capacity of up to 9089 mA h g−1 at the current density of 100 mA g−1. • The CuCo 2 S 4 electrode can still realize the high reversible capacity of 2254 mA h g−1 under the high current density of 2000 mA g−1. [ABSTRACT FROM AUTHOR]

Abstract Lithium−oxygen (Li−O 2) battery possesses remarkably high-energy density and is thus considered as an attractive system for next-generation energy storage. Here, a free-standing cathode is fabricated by directly growing mesoporous CoNi 2 S 4 nanorod arrays on carbon textiles (CNS-RAs/CT) by two-step hydrothermal procedures. This well-designed cathode structure based on mesoporous CNS-RAs owing large open space and high surface area provides sufficient void volume for depositing and accommodating copious Li 2 O 2 products and considerable amount of exposed catalytic sites for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The direct contact of CNS-RAs with high-conductive CT can also effectively boost electron transfer within the cathode. Benefiting from above unique features, the free-standing CNS-RAs/CT cathode achieves high capacity of 5438 mA h g−1, and excellent cycling stability of 588 cycles. Furthermore, the CNS-RAs/CT electrode-based bendable pouch-type Li−O 2 battery in a large scale is fabricated and shows potential feasibility as a flexible and wearable power source for next-generation electronic devices. Graphical abstract CoNi 2 S 4 nanorod array growing on the carbon textile is successfully fabricated and systematically studied for the first time as an integrated cathode to improve the stability of Li−O 2 battery. The large-area pouch-type Li−O 2 battery based integrated cathode exhibits potential feasibility as a flexible power source for next-generation electronic devices. Image 1 Highlights • CoNi 2 S 4 nanorod array growing on the carbon textile is successfully fabricated and systematically studied for the first time as an integrated cathode to improve the stability of Li−O 2 battery. • The free-standing CNS-RAs/CT cathode achieves high capacity of 5438 mA h g−1 and excellent cycling stability of 588 cycles. • The large-area pouch-type battery based integrated cathode exhibits potential feasibility as a flexible power source for next-generation electronic devices. [ABSTRACT FROM AUTHOR]

Abstract The interfacial interaction between catalysts and substrates has been considered as a pivotal factor determining the activities in different applications. However, interfacial interaction-dependent catalytic activities are currently neglected in understanding oxygen involved reaction in Li-O 2 battery, seriously restricting the development of high performance Li-O 2 battery. Herein, Ru@hierarchically porous carbon (Ru@HPC) with well-defined interfaces are fabricated and employed as cathode in Li-O 2 battery. Notably, Ru@HPC based Li-O 2 battery demonstrate better performance than that based on cathode formed by simply mixing Ru nanoparticles with hierarchically porous carbon (Ru/HPC). The Ru@HPC improved performance with a large specific capacity of ~7100 mA h g−1, high round-trip efficiency of 71%, high rate capability, and excellent cyclic stability of over 125 cycles (over 40 days). Density functional theory calculations indicated that the interfacial interaction between Ru nanoparticles and carbon substrate in Ru@HPC, which triggers electron transfer from ruthenium to carbon and thus optimizes the surface adsorption energy of the reactants and intermediate, facilitates the performance improvement of Li-O 2 battery. Our study for the first time reveals that the interfacial interaction between catalyst and substrate is a critical factor determining the Li-O 2 battery performance and offers a promising design strategy of catalyst for Li-O 2 batteries. Graphical abstract fx1 Highlights • Ru@hierarchically porous carbon (Ru@HPC) with well-defined interfaces are fabricated and employed as cathode in Li-O 2 battery. • The interfacial interaction-dependent catalytic activities are studied in understanding oxygen involved reaction in Li-O 2 battery. • The interfacial interaction between Ru nanoparticles and carbon substrate in Ru@HPC, which triggers electron transfer from ruthenium to carbon and thus optimizes the surface adsorption energy of the reactants and intermediate, facilitates the performance improvement of Li-O 2 battery. • Our study for the first time reveals that the interfacial interaction between catalyst and substrate is a critical factor determining the Li-O 2 battery performance and offers a promising design strategy of catalyst for Li-O 2 batteries. [ABSTRACT FROM AUTHOR]