Covalent Organic Frameworks with Tailored Functionalities for Modulating Surface Potentials in Triboelectric Nanogenerators.

Designing materials with high triboelectric is an efficient way of improving output performance of triboelectric nanogenerators (TENGs). Herein, we synthesized a series of covalent organic frameworks (COFs) with similar skeletons but various functional groups ranging between electron-donating and electron-withdrawing. These COFs form an ideal platform for clarifying the contribution of each group to TENG performance because the pore wall is perturbed in a predesigned manner. Kelvin probe force microscopy and computational data suggest that surface potentials and electron affinities of COFs can be improved by introducing electron-donating or withdrawing groups, with the highest values observed for fluorinated COF. The TENG with fluorinated COF delivered an output voltage and current of 420 V and 64 µA, respectively, which are comparable to other reported materials. This strategy can be used to efficiently screen suitable frameworks as TENG materials with excellent output performance.

Co-N heteroatomic interface engineering in peanut Shell-Derived porous carbon for enhanced oxygen reduction reaction.

The development of high-efficiency and low-cost oxygen reduction electrocatalysts have become an urgent need to push fuel cells into practical application. Herein, an effective electrocatalyst Co/NC was successfully constructed, which was derived from abundant peanut shells, obtained by doping with cobalt ions and pyrolyzing in NH3 atmosphere. Due to the abundant Co-N active sites triggered by Co-N heteroatomic interface, the prepared electrocatalysts present excellent oxygen reduction reaction (ORR) performance with more positive half-wave potential (E1/2 = 0.83 V), incremental limiting current density (JL = 5.45 mA cm-2), higher durability and stronger resistance to methanol, which is superior to that of Pt/C (E1/2 = 0.81 V and JL = 5.19 mA cm-2). This work proposes a potential strategy to synthesize efficient ORR electrocatalysts to instead of Pt-based catalysts.

Homogeneous and Fast Li-Ion Transport Enabled by a Novel Metal-Organic-Framework-Based Succinonitrile Electrolyte for Dendrite-Free Li Deposition.

Lithium (Li) metal has emerged as a promising electrode material for high-energy-density batteries. However, serious Li dendrite issues during cycling have plagued the safety and cyclability of the batteries, thus limiting the practical application of Li metal batteries. Herein, we prepare a novel metal-organic-framework-based (MOF-based) succinonitrile electrolyte, which enables homogeneous and fast Li-ion (Li+) transport for dendrite-free Li deposition. Given the appropriate aperture size of the MOF skeleton, the targeted electrolyte can allow only small-size Li+ to pass through its pores, which effectively guides uniform Li+ transport. Specially, Li ions are coordinated by the C═N of the MOF framework and the C≡N of succinonitrile, which could accelerate Li+ migration jointly. These characteristics afford an excellent quasi-solid-state electrolyte with a high ionic conductivity of 7.04 × 10-4 S cm-1 at room temperature and a superior Li+ transference number of 0.68. The Li/LiFePO4 battery with the MOF-based succinonitrile electrolyte exhibits dendrite-free Li deposition during the charge process, accompanied by a high capacity retention of 98.9% after 100 cycles at 0.1C.

Oxygen-deficient metal oxides supported nano-intermetallic InNi3C0.5 toward efficient CO2 hydrogenation to methanol.

Direct CO2 hydrogenation to methanol using renewable energy-generated hydrogen is attracting intensive attention, but qualifying catalysts represents a grand challenge. Pure-/multi-metallic systems used for this task usually have low catalytic activity. Here, we tailored a highly active and selective InNi3C0.5/ZrO2 catalyst by tuning the performance-relevant electronic metal-support interaction (EMSI), which is tightly linked with the ZrO2 type-dependent oxygen deficiency. Highly oxygen-deficient monoclinic-ZrO2 support imparts high electron density to InNi3C0.5 because of the considerably enhanced EMSI, thereby enabling InNi3C0.5/monoclinic-ZrO2 with an intrinsic activity three or two times as high as that of InNi3C0.5/amorphous-ZrO2 or InNi3C0.5/tetragonal-ZrO2 The EMSI-governed catalysis observed in the InNi3C0.5/ZrO2 system is extendable to other oxygen-deficient metal oxides, in particular InNi3C0.5/Fe3O4, achieving 25.7% CO2 conversion with 90.2% methanol selectivity at 325°C, 6.0 MPa, 36,000 ml gcat -1 hour-1, and H2/CO2 = 10:1. This affordable catalyst is stable for at least 500 hours and is also highly resistant to sulfur poisoning.

Nano-Intermetallic InNi3C0.5 Compound Discovered as a Superior Catalyst for CO2 Reutilization.

CO2 circular economy is urgently calling for the effective large-scale CO2 reutilization technologies. The reverse water-gas shift (RWGS) reaction is the most techno-economically viable candidate for dealing with massive-volume CO2 via downstream mature Fischer-Tropsch and methanol syntheses, but the desired groundbreaking catalyst represents a grand challenge. Here, we report the discovery of a nano-intermetallic InNi3C0.5 catalyst, for example, being particularly active, selective, and stable for the RWGS reaction. The InNi3C0.5(111) surface is dominantly exposed and gifted with dual active sites (3Ni-In and 3Ni-C), which in synergy efficiently dissociate CO2 into CO* (on 3Ni-C) and O* (on 3Ni-In). O* can facilely react with 3Ni-C-offered H* to form H2O. Interestingly, CO* is mainly desorbed at and above 400°C, whereas alternatively hydrogenated to CH3OH highly selectively below 300°C. Moreover, this nano-intermetallic can also fully hydrogenate CO-derived dimethyl oxalate to ethylene glycol (commodity chemical) with high selectivity (above 96%) and favorable stability.

Reaction-Induced Self-Assembly of CoO@Cu2 O Nanocomposites In†Situ onto SiC-Foam for Gas-Phase Oxidation of Bioethanol to Acetaldehyde.

A high-performance SiC-foam-structured nanocomposite catalyst of CoO@Cu2 O (i.e., 50-100 nm CoO partially covered with ca. 10 nm Cu2 O) was engineered from nano- to macro-scales in one step for the high-throughput gas-phase aerobic oxidation of bioethanol to acetaldehyde. This special CoO@Cu2 O nanostructure shows much higher activity/selectivity than other binary metal-oxide assemblies such as CuOx &CoO nano-mixtures or inverse Cu2 O@CoO nanostructures. The catalyst was facilely but exclusively obtainable by in situ reaction-induced transformation of the respective metal nitrates supported on SiC-foam into the CoO@Cu2 O nanostructure in the reaction stream. It achieved 95 % conversion with 98 % selectivity under mild conditions and was stable for at least 150 h for a feed of 20 vol % ethanol (much higher than in the literature: 1-6 vol %) at a high EtOH weight hourly space velocity of 8.5 h-1 . Abundant Cu2 O-CoO interfaces and high stability of the CoO@Cu2 O nanostructure were responsible for the high activity/selectivity and promising stability in this reaction.