MnO modified CNTs are applied as an efficient sulfur host to improve the performance of Li/S batteries due to the strong polysulfide adsorbability.

The large polarization of a Li−O 2 battery is derived from oxygen evolution reaction (OER) processe. To achieve a longlife Li−O 2 battery with high round-trip efficiency, various catalysts have been extensively investigated for oxygen cathodes, especially for OER processes. Here, we designed an in situ growth of α-MnO 2 /RuO 2 composite on a graphene nanosheet with a carbonembedded structure as the cathode electrode for a Li−O 2 battery. The synergistic catalytic effect between the α-MnO 2 and RuO 2 has significantly improved the OER kinetics. The fabricated Li−O 2 battery can deliver a high reversible capacity of 2895 mAh/g composite with a low charge overpotential of 0.25 V (0.34 V lower than bare RuO 2 cathode). The results revealed that more LiO 2 intermediates formed when α-MnO 2 was introduced into the RuO 2 electrode during the oxidation of Li 2 O 2 . The facilitation of the initial Li extraction was confirmed by density functional theory (DFT) calculations, which shows that the α-MnO 2 and RuO 2 interfaces can stabilize the primary Li ions and Li 2−x O 2 intermediates, respectively. Subsequently, Li 2−x O 2 would be easily oxidized to O 2 by RuO 2 catalyst. With the synergy between α-MnO 2 and RuO 2 , the initial delithiation process and O 2 evolution are promoted simultaneously. By combining theoretic and experimental results, we proposed a synergistic catalytic mechanism for the OER processes.

No abstract

Abundant transition metal borides are emerging as substitute electrochemical hydrogen evolution reaction (HER) catalysts for noble metals. In this study, we report on an unusual canonic-like behavior of the c lattice parameter in the AlB 2 -type solid solution Cr 1-x Mo x B 2 (x = 0, 0.25, 0.4, 0.5, 0.6, 0.75, 1) and its direct correlation to the HER activity in 0.5 M H 2 SO 4 solution. The activity increases with increasing x, reaching its maximum at x = 0.6 before decreasing again. At high current densities, Cr 0.4 Mo 0.6 B 2 outperforms Pt/C, as it needs 180 mV less overpotential to drive an 800 mA cm -2 current density. Cr 0.4 Mo 0.6 B 2 has excellent long-term stability and durability showing no significant activity loss after 5000 cycles and 25 hours of operation in acid. First-principle calculations have correctly reproduced the nonlinear dependence of c-lattice parameter and have shown that the mixed metal/B layers, such as (110), promote hydrogen evolution more efficiently for x = 0.6, supporting experimental results.

Surface modification and fabrication of composite structures have been reported to be efficient strategies to obtain cathode materials with satisfactory electrochemical performance.

No abstract

No abstract

No abstract