Lithium-sulfur (Li–S) batteries with high theoretical specific capacity of 1675 mAh g −1 and energy density of 2600 Wh kg −1 are considered as a promising candidate for energy conversion and storage devices in future. However, some critical dilemmas such as low real energy density , high solubility of ether-based electrolytes and slow redox kinetics of long-chain polysulfides remain unsettled hindering their development. Here we design and propose a high-performance sulfur host material constructed by growing CoN/Co 9 S 8 nanoparticles enclosed in reduced graphene oxide (RGO) and Co 9 S 8 modified separator to enhance the electrochemical performance of Li–S batteries . The results of first principal calculations confirm that the calculated adsorption energies of Li 2 S 8 , Li 2 S 6 , Li 2 S 4 and Li 2 S 2 on the Co 9 S 8 (111) surface are lower than that of the CoN (111) surface, indicating that the Co 9 S 8 has stronger adsorbing effect with polysulfides . Furthermore, the catalytic effect in Li 2 S 6 symmetric batteries and the nucleation of the Li 2 S tests display that the CoN/Co 9 S 8 @RGO has a fast conversion reaction kinetics and catalytic effect of polysulfides , thereby inhibiting the leakage of the polysulfides. Consequently, the S@CoN/Co 9 S 8 @RGO cathode with Co 9 S 8 layer represents a high discharge capacity of 1367.7 mAh g −1 at 0.1C and a prolonged lifespan over 700 cycles at 1 C with an extremely low decay rate of 0.06 % per cycle and high cycling stability.
Designing carbon-free electrocatalysts that can efficiently drive hydrogen evolution (HER), oxygen evolution (OER), and zinc-air battery (ZAB) reactions in alkaline media remains difficult because of the different kinetic requirements of each process. Herein, we demonstrates a carbon-free crystalline-amorphous (C-A) Cu 0.81 Ni 0.19 @CoN/Mo 2 N heterostructured nanosheets synthesized through a single-step annealing method that simultaneously forms a crystalline alloy core and an amorphous nitride shell. This direct route eliminates carbon supports and avoids multi-stage alloying or nitridation, resulting in tightly coupled C–A interfaces that accelerate charge transfer and stabilize active sites. The catalyst delivers low overpotentials of 43 mV for HER and 297 mV for OER at 10 mA cm −2 , enabling an overall water splitting (OWS) low voltage of 1.56 V. It also maintains excellent durability under harsh electrochemical conditions owing to the absence of carbon, mitigating agglomeration and degradation. Density functional theory calculations reveal that the Cu 0.81 Ni 0.19 /CoN optimizes hydrogen adsorption, while the Cu 0.81 Ni 0.19 /Mo 2 N promotes oxygen intermediate formation. Integrated into a flexible ZAB, the catalyst exhibits a high specific capacity of 811.6 mAh g −1 , a small voltage gap of 1.15 V at 50 mA cm −2 , and 150 h of stable cycling. A self-powered system coupling this flexible ZAB-OWS system further demonstrates the practical viability of this one-step-engineered C–A heterostructure for sustainable energy applications.
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