Single-atom catalysts (SACs) with 100% active sites have excellent prospects for application in the oxygen evolution reaction (OER). However, further enhancement of the catalytic activity for OER is quite challenging, particularly for the development of stable SACs with overpotentials <180 mV. Here, we report an iridium single atom on Ni 2 P catalyst (Ir SA -Ni 2 P) with a record low overpotential of 149 mV at a current density of 10 mA•cm −2 in 1.0 M KOH. The Ir SA -Ni 2 P catalyst delivers a current density up to ∼28-fold higher than that of the widely used IrO 2 at 1.53 V vs RHE. Both the experimental results and computational simulations indicate that Ir single atoms preferentially occupy Ni sites on the top surface. The reconstructed Ir−O−P/Ni−O−P bonding environment plays a vital role for optimal adsorption and desorption of the OER intermediate species, which leads to marked enhancement of the OER activity. Additionally, the dynamic "top-down" evolution of the specific structure of the Ni@Ir particles is responsible for the robust single-atom structure and, thus, the stability property. This Ir SA -Ni 2 P catalyst offers novel prospects for simplifying decoration strategies and further enhancing OER performance.

The electrochemical nitrate reduction reaction (NITRR) is an appealing method for ammonia synthesis, owing to the ambient conditions as well as its abundant sources, low dissociation energy, and high solubility of nitrate. The hydrogen evolution reaction is a competing process of the NITRR, which should be properly suppressed to achieve a high Faradaic efficiency of the NITRR. Herein, ultrathin CoO x nanosheets with abundant surface oxygen are designed as a low-cost NITRR catalyst, which delivers an ultrahigh ammonia yield of 82.4 ± 4.8 mg h −1 mg cat −1 with a Faradaic efficiency of 93.4 ± 3.8% at −0.3 V versus the reversible hydrogen electrode. Theoretical calculation reveals that the surface oxygen on cobalt sites can stabilize the adsorbed hydrogen on cobalt oxide, which hampers the evolution of hydrogen and leads to an enhanced NITRR activity. This work demonstrates that surface modification plays a critical role in suppressing the HER and facilitating the NITRR through a NHO pathway with a lower energy barrier.

The sodium (potassium)‐metal anodes combine low‐cost, high theoretical capacity, and high energy density, demonstrating promising application in sodium (potassium)‐metal batteries. However, the dendrites’ growth on the surface of Na (K) has impeded their practical application. Herein, density functional theory (DFT) results predict Na2Te/K2Te is beneficial for Na+/K+ transport and can effectively suppress the formation of the dendrites because of low Na+/K+ migration energy barrier and ultrahigh Na+/K+ diffusion coefficient of 3.7 × 10−10 cm2 s−1/1.6 × 10−10 cm2 s−1 (300 K), respectively. Then a Na2Te protection layer is prepared by directly painting the nanosized Te powder onto the sodium‐metal surface. The Na@Na2Te anode can last for 700 h in low‐cost carbonate electrolytes (1 mA cm−2, 1 mAh cm−2), and the corresponding Na3V2 (PO4)3//Na@Na2Te full cell exhibits high energy density of 223 Wh kg−1 at an unprecedented power density of 29687 W kg−1 as well as an ultrahigh capacity retention of 93% after 3000 cycles at 20 C. Besides, the K@K2Te‐based potassium‐metal full battery also demonstrates high power density of 20 577 W kg−1 with energy density of 154 Wh kg−1. This work opens up a new and promising avenue to stabilize sodium (potassium)‐metal anodes with simple and low‐cost interfacial layers.

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Program code is a precious asset to its owner. Due to the easyto-reverse nature of Java, code protection for Android apps is of particular importance. To this end, code obfuscation is widely utilized by both legitimate app developers and malware authors, which complicates the representation of source code or machine code in order to hinder the manual investigation and code analysis. Despite many previous studies focusing on the obfuscation techniques, however, our knowledge on how obfuscation is applied by realworld developers is still limited.In this paper, we seek to better understand Android obfuscation and depict a holistic view of the usage of obfuscation through a large-scale investigation in the wild. In particular, we focus on four popular obfuscation approaches: identifier renaming, string encryption, Java reflection, and packing. To obtain the meaningful statistical results, we designed efficient and lightweight detection models for each obfuscation technique and applied them to our massive APK datasets (collected from Google Play, multiple thirdparty markets, and malware databases). We have learned several interesting facts from the result. For example, malware authors use string encryption more frequently, and more apps on third-party markets than Google Play are packed. We are also interested in the explanation of each finding. Therefore we carry out in-depth code analysis on some Android apps after sampling. We believe our study will help developers select the most suitable obfuscation approach, and in the meantime help researchers improve code analysis systems in the right direction.

Covalent organic frameworks (COFs) are an emerging class of crystalline porous materials with tailor-made functionalities for improved photocatalytic activity. However, limited choice of building blocks greatly restricts the photochemical performance and application scope of COFs in photocatalysis. Herein, a covalent hybridization approach is reported to address these issues by knitting rigid macrocyclic struts, namely, pillararenes, into the extended network of COFs. Varying different ratios of pillararenes with unique conformations and electron-rich cavities can not only generate a confined molecular space for exciton migration and carrier transport but also create new interfaces to interplay with photogenerated charge carriers, leading to high performance in promoting efficient oxidation of amines to imines. This work paves the way for constructing macrocycle-derived COFs and provides a promising molecular platform for photocatalysis through predesign and functionalization of the pore surface.

Electrochemical nitrate reduction has become an appealing “waste-to-wealth” approach for sustainable NH3 synthesis owing to its mild operating conditions. However, developing catalysts with high activities and Faradaic efficiencies for this complicated eight-electron reaction is a great challenge. Herein, bismuth ferrite (BiFeO3) flakes, with a distorted perovskite-type structure, are demonstrated to be excellent catalysts for electrochemical NH3 synthesis via nitrate reduction, with a maximum Faradaic efficiency of 96.85%, NH3 yield of 90.45 mg h–1 mgcat –1, at −0.6 V vs. reversible hydrogen electrode. During the nitrate reduction reaction, the crystalline BiFeO3 rapidly converts into an amorphous phase, which is stable in the long term reaction. These results open a new window for rational design of more active and durable electrocatalysts.

The electrochemical nitrate reduction reaction (NO3RR) is a promising alternative synthetic route for sustainable ammonia (NH3) production, because it not only eliminates nitrate (NO3 –) from water but also produces NH3 under mild operating conditions. However, owing to the complicated eight-electron reaction and the competition from the hydrogen evolution reaction, developing catalysts with high activities and Faradaic efficiencies (FEs) is highly imperative to improve the reaction performance. In this study, Cu-doped Fe3O4 flakes are fabricated and demonstrated to be excellent catalysts for electrochemical conversion of NO3 – to NH3, with a maximum FE of ∼100% and an NH3 yield of 179.55 ± 16.37 mg h–1 mgcat –1 at −0.6 V vs RHE. Theoretical calculations reveal that doping the catalyst surface with Cu results in a more thermodynamically facile reaction. These results highlight the feasibility of promoting the NO3RR activity using heteroatom doping strategies.