RESUMO
Sodium-ion batteries (SIBs) have gradually become one of the most promising energy storage techniques in the current era of post-lithium-ion batteries. For anodes, transitional metal selenides (TMSe) based materials are welcomed choices , owing to relatively higher specific capacities and enriched redox active sites. Nevertheless, current bottlenecks are blamed for their poor intrinsic electronic conductivities, and uncontrollable volume expansion during redox reactions. Given that, an interfacial-confined isochronous conversion strategy is proposed, to prepare orthorhombic/cubic biphasic TMSe heterostructure, namely CuSe/Cu3 VSe4 , through using MXene as the precursor, followed by Cu/Se dual anchorage. As-designed biphasic TMSe heterostructure endows unique hierarchical structure, which contains adequate insertion sites and diffusion spacing for Na ions, besides, the surficial pseudocapacitive storage behaviors can be also proceeded like 2D MXene. By further investigation on electronic structure, the theoretical calculations indicate that biphasic CuSe/Cu3 VSe4 anode exhibits well-enhanced properties, with smaller bandgap and thus greatly improves intrinsic poor conductivities. In addition, the dual redox centers can enhance the electrochemical Na ions storage abilities. As a result, the as-designed biphasic TMSe anode can deliver a reversible specific capacity of 576.8 mAh g-1 at 0.1 A g-1 , favorable Na affinity, and reduced diffusion barriers. This work discloses a synchronous solution toward demerits in conductivities and lifespan, which is inspiring for TMSe-based anode development in SIBs systems.
RESUMO
Developing efficient electrocatalysts for water splitting is of great significance for realizing sustainable energy conversion. In this work, Ru sub-nanoclusters anchored on cobalt-nickel bimetallic phosphides (Ru-CoP/Ni2P) are constructed by an interfacial confinement strategy. Remarkably, Ru-CoP/Ni2P with low noble metal loading (33.1 µg cm-2) shows superior activity for hydrogen evolution reaction (HER) in all pH values, whose turnover frequency (TOF) is 8.7, 15.3, and 124.7 times higher than that of Pt/C in acidic, alkaline, and neutral conditions, respectively. Meanwhile, it only requires the overpotential of 171 mV@10 mA cm-2 for oxygen evolution reaction (OER) and corresponding TOF is 20.3 times higher than that of RuO2. More importantly, the Ru-CoP/Ni2P||Ru-CoP/Ni2P displays superior mass activity of 4017 mA mgnoble metal -1 at 2.0 V in flowing alkaline water electrolyzer, which is 105.1 times higher than that of Pt/C||IrO2. In situ Raman spectroscopy demonstrates that the Ru sites in Ru-CoP/Ni2P play a key role for water splitting and follow the adsorption evolution mechanism toward OER. Further mechanism studies disclose the confined Ru atom contributes to the desorption of H2 during HER and the formation of O-O bond during OER, leading to fast reaction kinetics. This study emphasizes the importance of interface confinement for enhancing electrocatalytic activity.
RESUMO
A design of coaxial hollow nanocables of carbon nanotubes and silicon composite (CNTs@Silicon) was presented, and the lithiation/delithiation behavior was investigated. The FIB-SEM studies demonstrated hollow structured silicon tends to expand inward and shrink outward during lithiation/delithiation, which reveal the mechanism of inhibitive effect of the excessive growth of solid-electrolyte interface by hollow structured silicon. The as-prepared coaxial hollow nanocables demonstrate an impressive reversible specific capacity of 1150 mAh g-1 over 500 cycles, giving an average Coulombic efficiency of >99.9%. The electrochemical impedance spectroscopy and differential scanning calorimetry confirmed the SEI film excessive growth is prevented.