Dual-Phasic Carbon with Co Single Atoms and Nanoparticles as a Bifunctional Oxygen Electrocatalyst for Rechargeable Zn–Air Batteries

The great interest in rechargeable Zn–air batteries (ZABs) arouses extensive research on low-cost, high-active, and durable bifunctional electrocatalysts to boost the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). It remains a great challenge to simultaneously host high-active and independent ORR and OER sites in a single catalyst. Herein a dual-phasic carbon nanoarchitecture consisting of a single-atom phase for the ORR and nanosized phase for the OER is proposed. Specifically, single Co atoms supported on carbon nanotubes (single-atom phase) and nanosized Co encapsulated in zeolitic-imidazole-framework-derived carbon polyhedron (nanosized phase) are integrated together via carbon nanotube bridges. The obtained dual-phasic carbon catalyst shows a small overpotential difference of 0.74 V between OER potential at 10 mA cm⁻² and ORR half-wave potential. The ZAB based on the bifunctional catalyst demonstrates a large power density of 172 mW cm⁻². Furthermore, it shows a small charge-discharge potential gap of 0.51 V at 5 mA cm⁻² and outstanding discharge-charge cycling durability. This study provides a feasible design concept to achieve multifunctional catalysts and promotes the development of rechargeable ZABs.     

Low-Cost,Safe, and Ultra-Long Cycle Life Zn–K Hybrid Ion Batteries

Zinc-ion batteries (ZIBs) are viewed as a promising energy storage system for large-scale applications thanks to the low cost and wide accessibility of Zn-based materials, the high theoretical capacity of Zn anode, and their high level of safety. However, the practical application of ZIBs is hindered by the rapid performance degradation. Herein, a Zn–K hybrid ion battery design is proposed using a high-quality Prussian blue cathode and a nonflammable Zn–K hybrid ion electrolyte. The electrochemical process is divided into two parts, with K⁺ insertion/extraction occurring at the cathode side and Zn²⁺ plating/stripping occurring at the anode side, which avoids structure destruction caused by Zn²⁺ insertion in the cathode. The non-flammable electrolyte not only ensures high safety but also effectively suppresses dendrite growth on the Zn anode. The hybrid cells demonstrate a high capacity of 151.0 mAh g⁻¹, a high voltage of 1.74 V (vs Zn²⁺/Zn), and an ultra-long cycle life of 15 000 cycles. Combining the nonflammable nature of the electrolyte, the abundance of raw materials, and good electrochemical performance, the Zn–K hybrid ion battery system promises a promising future for renewable energy storage applications.     

High-Loading Co Single Atoms and Clusters Active Sites toward Enhanced Electrocatalysis of Oxygen Reduction Reaction for High-Performance Zn–Air Battery

The development of precious-metal alternative electrocatalysts for oxygen reduction reaction (ORR) is highly desired for a variety of fuel cells, and single atom catalysts (SACs) have been envisaged to be the promising choice. However, there remains challenges in the synthesis of high metal loading SACs (>5 wt.%), thus limiting their electrocatalytic performance. Herein, a facile self-sacrificing template strategy is developed for fabricating Co single atoms along with Co atomic clusters co-anchored on porous-rich nitrogen-doped graphene (Co SAs/AC@NG), which is implemented by the pyrolysis of dicyandiamide with the formation of layered g-C₃N₄ as sacrificed templates, providing rich anchoring sites to achieve high Co loading up to 14.0 wt.% in Co SAs/AC@NG. Experiments combined with density functional theory calculations reveal that the co-existence of Co single atoms and clusters with underlying nitrogen doped carbon in the optimized Co₄₀SAs/AC@NG synergistically contributes to the enhanced electrocatalysis for ORR, which outperforms the state-of-the-art Pt/C catalysts with presenting a high half-wave potential (E_1/2 = 0.890 V) and robust long-term stability. Moreover, the Co₄₀SAs/AC@NG presents excellent performance in Zn–air battery with a high-peak power density (221 mW cm⁻²) and strong cycling stability, demonstrating great potential for energy storage applications.     

Rational Engineering CoxOy Nanosheets via Phosphorous and Sulfur Dual-Coupling for Enhancing Water Splitting and Zn–Air Battery

Herein, an efficient multifunctional catalyst based on phosphorus and sulfur dual-doped cobalt oxide nanosheets supported by Cu@CuS nanowires is developed for water splitting and Zn–air batteries. The formation of such a unique heterostructure not only enhances the number and type of electroactive sites, but also leads to modulated electronic structure, which produces reasonable adsorption energy toward the reactant, thereby improving electrocatalytic efficiency. The catalyst demonstrates small overpotentials of 116 and 280 mA cm⁻² to achieve 10 mA cm⁻² for hydrogen and oxygen evolution, respectively. As a result, a developed electrolyzer displays a cell voltage of 1.52 V at 10 mA cm⁻² and long-term stability with a current response of 92.3% after operating for 30 h. Moreover, using such a catalyst in the fabrication of a Zn–air battery also leads to a cell voltage of 1.383 V, along with a power density of 130 mW cm⁻² at 220 mA cm⁻².     

High-Density Atomic Fe–N4/C in Tubular,Biomass-Derived,Nitrogen-Rich Porous Carbon as Air-Electrodes for Flexible Zn–Air Batteries

Developing low-cost single-atom catalysts (SACs) with high-density active sites for oxygen reduction/evolution reactions (ORR/OER) are desirable to promote the performance and application of metal–air batteries. Herein, the Fe nanoparticles are precisely regulated to Fe single atoms supported on the waste biomass corn silk (CS) based porous carbon for ORR and OER. The distinct hierarchical porous structure and hollow tube morphology are critical for boosting ORR/OER performance through exposing more accessible active sites, providing facile electron conductivity, and facilitating the mass transfer of reactant. Moreover, the enhanced intrinsic activity is mainly ascribed to the high Fe single-atom (4.3 wt.%) loading content in the as-synthesized catalyst.Moreover, the ultra-high N doping (10 wt.%) can compensate the insufficient OER performance of conventional Fe N C catalysts. When as-prepared catalysts are assembled as air-electrodes in flexible Zn–air batteries, they perform a high peak power density of 101 mW cm⁻², a stable discharge–charge voltage gap of 0.73 V for >44 h, which shows a great potential for Zinc–air battery. This work provides an avenue to transform the renewable low-cost biomass materials into bifunctional electrocatalysts with high-density single-atom active sites and hierarchical porous structure.     

Engineering Crystallinity and Oxygen Vacancies of Co(II) Oxide Nanosheets for High Performance and Robust Rechargeable Zn–Air Batteries

Efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes highly rely on the rational design and synthesis of high-performance electrocatalysts. Herein, comprehensive characterizations and density functional theory (DFT) calculations are combined to verify the important roles of the crystallinity and oxygen vacancy levels of Co(II) oxide (CoO) on ORR and OER activities. A facile and controllable vacuum-calcination strategy is utilized to convert Co(OH)₂ into oxygen-defective amorphous-crystalline CoO (namely ODAC-CoO) nanosheets. With the carefully controlled crystallinity and oxygen vacancy levels, the optimal ODAC-CoO sample exhibits dramatically enhanced ORR and OER electrocatalytic activities compared with the pure crystalline CoO counterpart. The assembled liquid and quasi-solid-state Zn–air batteries with ODAC-CoO as cathode material achieve remarkable specific capacity, power density, and excellent cycling stability, outperforming the benchmark Pt/C + IrO₂ catalysts. This study theoretically proposes and experimentally demonstrates that the simultaneous introduction of amorphous structures and oxygen vacancies could be an effective avenue towards high-performance electrocatalytic ORR and OER.     

A 132 Mb/s, 1bit 4224 M samples/s sub-sampling, low-complexity and energy-efficient BPSK transceiver for all-digital 3–5 GHz IR-UWB

In this paper, a 3–5 GHz impulse radio ultra wideband BPSK transceiver is presented. A new all-digital architecture is applied in the proposed transceiver. The transceiver has no mixer and low complexity. The transmitter employs a RLC network response filter to achieve the adjustable pulse parameters, which includes pulse width, pulse bandwidth and pulse amplitude. Considering the low duty ratio, a proposed on/off output buffer in the transmitter is applied to save the power consumption. To simplify the receiver, the radio frequency input signal is amplified and sampled directly by a 1bit 4224 MHz sub-sampling ADC. The ADC comprises by 16 paralleled comparators for low power. Each comparator operates at 264 MHz and can be self-calibrated. The transceiver is implemented in SMIC 0.13 μm CMOS process at the supply of 1.2 V. The measured results show the adjustable parameters: the pulse amplitude is from 110 to 370 mV, the pulse width is from 900 to 1,600 ns and the pulse bandwidth is from 2.0 to 2.78 GHz. The data rate is 132 Mb/s between the transceiver. The transmitter and the receiver only consume 18.2 and 330 pJ/pulse, respectively. The receiver sensitivity is ?75 dBm at the bit error rate of 10^?3.