Metallic zinc as a rechargeable anode material for aqueous batteries has gained tremendous attention. Zn-air batteries, which operate in alkaline electrolytes, are promising with the highest theoretical volumetric energy density. However, rechargeable zinc anodes develop slowly in alkaline electrolytes due to passivation, dissolution, and hydrogen evolution issues. In this study, we report the design of a submicron zinc anode sealed with an ion-sieving coating that suppresses hydrogen evolution reaction. The design is demonstrated with ZnO nanorods coated by TiO 2 , which overcomes passivation, dissolution, and hydrogen evolution issues simultaneously. It achieves superior reversible deep cycling performance with a high discharge capacity of 616 mAh/g and Coulombic efficiency of 93.5% when cycled with 100% depth of discharge at lean electrolyte. It can also deeply cycle ∼350 times in a beaker cell. The design principle of this work may potentially be applied to other battery electrode materials.
Zinc–bromine flow batteries are promising for stationary energy storage, and bromine‐complexing agents have been used to form phase‐separated liquid polybromide products. However, an understanding of the dynamics of polybromide nucleation is limited due to the beam sensitivity and complexity of polybromides. Here we report an in operando platform composed of dark‐field light microscopy and a transparent electrochemical cell to reveal the dynamics of polybromide formation in their native environment. Using our platform, we confirm and reveal the liquid nature, chemical composition, pinning effect (strong interaction with Pt), residual effect (residual charge products on the surface), self‐discharging, and over‐oxidation of the polybromide products. The results provide insights into the role of complexing agents and guide the future design of zinc–bromine flow batteries. Furthermore, our in operando platform can potentially be used to study sensitive species and phases in other electrochemical reactions.
Photocatalytic conversion of nitrogen to ammonia is a green alternative for the Haber-Bosch process. The current progress in photocatalytic nitrogen reduction suggests, however, that there exists a large gap in performance before commercial use is viable. One of the major challenges is that no highly active photocatalysts exist. Furthermore, the development of photocatalysts is greatly hindered by false positives or non-reproducible data. Here, we will describe the current known causes of non-reproducible results in the literature and present solutions to mitigate these false positive results. Finally, we highlight the main challenges that remain for photocatalytic nitrogen fixation. We aim to help researchers design more reliable experiments and inspire practical research in developing photocatalytic ammonia synthesis.
Rechargeable zinc–air batteries are attracting great attention due to their high theoretical specific energy, safety, and economic viability. However, their performance and large-scale practical applications are largely limited by poor durability and high overpotential on the air-cathode due to the slow kinetics of the oxygen evolution and reduction reactions (OER/ORR). Therefore, it is highly desired to develop new bifunctional catalysts to improve the OER and ORR kinetics. In this paper, NiCo2Se4 nanowires were uniformly grown on carbon fiber paper (CFP) for the first time. With an overpotential for OER of 327 mV, NiCo2Se4 nanowires show a better performance than RuO2 (350 mV) and a high stability. Moreover, their half-wave potential of 0.77 V and limiting current density of 3.75 mA·cm−2 make it a promising non-precious-metal catalyst for ORR, with performance close to Pt/C (0.87 V, 3.7 mA·cm−2). The excellent performance is attributed to the nanowire morphology with efficient 1D electronic pathways, high conductivity of NiCo2Se4 and an enhanced electronic structure, thanks to a mixed valence of nickel and cobalt ions.
Zinc–bromine flow batteries are promising for stationary energy storage, and bromine‐complexing agents have been used to form phase‐separated liquid polybromide products. However, an understanding of the dynamics of polybromide nucleation is limited due to the beam sensitivity and complexity of polybromides. Here we report an in operando platform composed of dark‐field light microscopy and a transparent electrochemical cell to reveal the dynamics of polybromide formation in their native environment. Using our platform, we confirm and reveal the liquid nature, chemical composition, pinning effect (strong interaction with Pt), residual effect (residual charge products on the surface), self‐discharging, and over‐oxidation of the polybromide products. The results provide insights into the role of complexing agents and guide the future design of zinc–bromine flow batteries. Furthermore, our in operando platform can potentially be used to study sensitive species and phases in other electrochemical reactions.
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