The worldwide unrestrained emission of carbon dioxide (CO2) has caused serious environmental pollution and climate change issues. For the sustainable development of human civilization, it is very desirable to convert CO2 to renewable fuels through clean and economical chemical processes. Recently, electrocatalytic CO2 conversion is regarded as a prospective pathway for the recycling of carbon resource and the generation of sustainable fuels. In this review, recent research advances in electrocatalytic CO2 reduction are summarized from both experimental and theoretical aspects. The referred electrocatalysts are divided into different classes, including metal–organic complexes, metals, metal alloys, inorganic metal compounds and carbon‐based metal‐free nanomaterials. Moreover, the selective formation processes of different reductive products, such as formic acid/formate (HCOOH/HCOO−), monoxide carbon (CO), formaldehyde (HCHO), methane (CH4), ethylene (C2H4), methanol (CH3OH), ethanol (CH3CH2OH), etc. are introduced in detail, respectively. Owing to the limited energy efficiency, unmanageable selectivity, low stability, and indeterminate mechanisms of electrocatalytic CO2 reduction, there are still many tough challenges need to be addressed. In view of this, the current research trends to overcome these obstacles in CO2 electroreduction field are summarized. We expect that this review will provide new insights into the further technique development and practical applications of CO2 electroreduction.

Lithium-sulfur batteries (Li-S) have attracted soaring attention due to the particularly high energy density for advanced energy storage system. However, the practical application of Li-S batteries still faces multiple challenges, including the shuttle effect of intermediate polysulfides, the low conductivity of sulfur and the large volume variation of sulfur cathode. To overcome these issues, here we reported a self-templated approach to prepare interconnected carbon nanotubes inserted/wired hollow CoS nanoboxes (CNTs/CoS-NBs) as an efficient sulfur host material. Originating from the combination of three-dimensional CNT conductive network and polar CoS-NBs, the obtained hybrid nanocomposite of CNTs/CoS-NBs can offer ultrahigh charge transfer properties, and efficiently restrain polysulfides in hollow CoS-NBs via the synergistic effect of structural confinement and chemical bonding. Benefiting from the above advantages, the S@CNTs/CoS-NBs cathode shows a significantly improved electrochemical performance in terms of high reversible capacity, good rate performance, and long-term cyclability. More remarkably, even at an elevated temperature (50 °C), it still exhibits high capacity retention and good rate capacity.

The catalytic conversion of nitrogen to ammonia is one of the most important processes in nature and chemical industry. However, the traditional Haber-Bosch process of ammonia synthesis consumes substantial energy and emits a large amount of carbon dioxide. Solar-driven nitrogen fixation holds great promise for the reduction of energy consumption and environmental pollution. On the basis of both experimental results and density functional theory calculations, here we report that the oxygen vacancy engineering on ultrathin BiOBr nanosheets can greatly enhance the performance for photocatalytic nitrogen fixation. Through the addition of polymetric surfactant (polyvinylpyrrolidone, PVP) in the synthesis process, V O-BiOBr nanosheets with desirable oxygen vacancies and dominant exposed {001} facets were successfully prepared, which effectively promote the adsorption of inert nitrogen molecules at ambient condition and facilitate the separation of photoexcited electrons and holes. The oxygen defects narrow the bandgap of V O-BiOBr photocatalyst and lower the energy requirement of exciton generation. In the case of the specific surface areas are almost equal, the V O-BiOBr nanosheets display a highly improved photocatalytic ammonia production rate (54.70 μmol·g–1·h–1), which is nearly 10 times higher than that of the BiOBr nanoplates without oxygen vacancies (5.75 μmol·g–1·h–1). The oxygen vacancy engineering on semiconductive nanomaterials provides a promising way for rational design of catalysts to boost the rate of ammonia synthesis under mild conditions.

Rechargeable magnesium batteries have attracted increasing attention due to the high theoretical volumetric capacities, dendrite formation-free characteristic and low cost of Mg metal anodes. However, the development of magnesium batteries is seriously hindered by the lack of capable cathode materials with long cycling life and fast solid-state diffusion kinetics for highly-polarized divalent Mg ions. Herein, vanadium tetrasulfide (VS ) with special one-dimensional atomic-chain structure is reported to be able to serve as a favorable cathode material for high-performance magnesium batteries. Through a surfactant-assisted solution-phase process, sea-urchin-like VS nanodendrites are controllably prepared. Benefiting from the chain-like crystalline structure of VS , the S dimers in the VS nanodendrites provide abundant sites for Mg insertion. Moreover, the VS atomic-chains bonded by weak van der Waals forces are beneficial to the diffusion kinetics of Mg ions inside the open channels of VS . Through a series of systematic ex situ characterizations and density functional theory calculations, the magnesiation/demagnesiation mechanism of VS are elucidated. The VS nanodendrites present remarkable performance for Mg storage among existing cathode materials, exhibiting a remarkable initial discharge capacity of 251 mAh g at 100 mA g and an impressive long-term cyclability at large current density of 500 mA g (74 mAh g after 800 cycles).

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