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NH 3 synthesis by the electrocatalytic N 2 reduction reaction (NRR) under ambient conditions is an appealing alternative to the currently employed industrial method-the Haber-Boschp rocess-that requires high temperature and pressure.W er eport single Mo atoms anchored to nitrogendoped porous carbon as ac ost-effective catalyst for the NRR. Benefiting from the optimally high density of active sites and hierarchically porous carbon frameworks,t his catalyst achieves ah igh NH 3 yield rate (34.0 AE 3.6 mg NH 3 h À1 mg cat. À1 )a nd ahigh Faradaic efficiency (14.6 AE 1.6 %) in 0.1m KOHatroom temperature.T hese values are considerably higher compared to previously reported non-precious-metal electrocatalysts. Moreover,t his catalyst displays no obvious current drop during a5 0000 sN RR, and high activity and durability are achieved in 0.1m HCl. The findings provideapromising lead for the design of efficient and robust single-atom non-preciousmetal catalysts for the electrocatalytic NRR.

The increasing demands of energy storage require the significant improvement of current Li-ion battery electrode materials and the development of advanced electrode materials. Thus, it is necessary to gain an in-depth understanding of the reaction processes, degradation mechanism, and thermal decomposition mechanisms of electrode materials under realistic operation conditions. This understanding can be obtained by in situ/operando characterization techniques that provide information on the structure evolution, redox mechanism, solid-electrolyte interphase (SEI) formation, side reactions and Li-ion transport properties under operating conditions. Here, the recent developments in the in situ/operando techniques employed for the investigation of the structural stability, dynamic properties, chemical environment changes and morphological evolution during electrochemical processes are described and summarized in detail. The experimental approaches reviewed in this paper include X-ray, electron, neutron, optical, and scanning probes. Each advanced technique has unique capabilities to study specific properties of electrode materials within specific limitations. The experimental methods and operating principles, especially the in situ cell designs, are described in detail. To illustrate the applicability and uniqueness of each technique, representative studies making use of the in situ/operando techniques are discussed and summarized. Finally, the major current challenges and future opportunities of the in situ/operando techniques are discussed. Several important battery challenges are likely to benefit from these in situ/operando techniques, including the inhomogeneous reactions of This article is protected by copyright. All rights reserved. 4high energy density cathodes, the development of safe and reversible Li metal plating and the development of stable SEI on electrodes.Received: ((will be filled in by the editorial staff))Revised: ((will be filled in by the editorial staff))

Rechargeable lithium-ion batteries with high energy density that can be safely charged and discharged at high rates are desirable for electrified transportation and other applications 1-3. However, the sub-optimal intercalation potentials of current anodes result in a trade-off between energy density, power and safety. Here we report that disordered rock salt 4,5 Li3+xV2O5 can be used as a fast-charging anode that can reversibly cycle two lithium ions at an average voltage of about 0.6 volts versus a Li/Li + reference electrode. The increased potential compared to graphite 6,7 reduces the likelihood of lithium metal plating if proper charging controls are used, alleviating a major safety concern (short-circuiting related to Li dendrite growth). In addition, a lithium-ion battery with a disordered rock salt Li3V2O5 anode yields a cell voltage much higher than does a battery using a commercial fastcharging lithium titanate anode or other intercalation anode candidates (Li3VO4 and LiV0.5Ti0.5S2) 8,9. Further, disordered rock salt Li3V2O5 can perform over 1,000 charge-discharge cycles with negligible capacity decay and exhibits exceptional rate capability, delivering over 40 per cent of its capacity in 20 seconds. We attribute the low voltage and high rate capability of disordered rock salt Li3V2O5 to a redistributive lithium intercalation mechanism with low energy barriers revealed via ab initio calculations. This low-potential, high-rate intercalation reaction can be used to identify other metal oxide anodes for fast-charging, long-life lithium-ion batteries.

The development of highly active and durable catalysts for electrochemical reduction of CO2 (ERC) to CH4 in aqueous media is an efficient and environmentally friendly solution to address global problems in energy and sustainability. In this work, an electrocatalyst consisting of single Zn atoms supported on microporous N-doped carbon was designed to enable multielectron transfer for catalyzing ERC to CH4 in 1 M KHCO3 solution. This catalyst exhibits a high Faradaic efficiency (FE) of 85%, a partial current density of −31.8 mA cm–2 at a potential of −1.8 V versus saturated calomel electrode, and remarkable stability, with neither an obvious current drop nor large FE fluctuation observed during 35 h of ERC, indicating a far superior performance than that of dominant Cu-based catalysts for ERC to CH4. Theoretical calculations reveal that single Zn atoms largely block CO generation and instead facilitate the production of CH4.