Synergetic Effect of Liquid and Solid Catalysts on the Energy Efficiency of Li–O₂ Batteries: Cell Performances and Operando STEM Observations

The sluggish cathodic kinetics and lower energy efficiency, associated with solid and insulating discharge products of Li2O2, are the key factors that prevent the practical implementation of Li–O2 batteries (LOBs). Here we demonstrate that the combination of the solid catalyst (RuO2) and soluble redox mediator tetrathiafulvalene (TTF) exhibits a synergetic effect in improving the cathodic kinetics and energy efficiency of LOBs by reducing both charge and discharge overpotentials. Operando electron microscopy observations and electrochemical measurements reveal that RuO2 not only exhibits bifunctional catalysis for Li–O2 reactions but also benefits the catalytic efficiency of TTF. Meanwhile, TTF plays an important role in activating the Li2O2 passivated RuO2 catalysts and in helping RuO2 effectively oxidize the discharge products during charging. The synergetic effect of solid and liquid catalysts, beyond traditional bifunctional catalysis, obviously increases the cathodic kinetics and round-trip energy efficiency of LOBs

Synergetic Effect of Liquid and Solid Catalysts on the Energy Efficiency of Li–O₂ Batteries: Cell Performances and Operando STEM Observations

The sluggish cathodic kinetics and lower energy efficiency, associated with solid and insulating discharge products of Li2O2, are the key factors that prevent the practical implementation of Li–O2 batteries (LOBs). Here we demonstrate that the combination of the solid catalyst (RuO2) and soluble redox mediator tetrathiafulvalene (TTF) exhibits a synergetic effect in improving the cathodic kinetics and energy efficiency of LOBs by reducing both charge and discharge overpotentials. Operando electron microscopy observations and electrochemical measurements reveal that RuO2 not only exhibits bifunctional catalysis for Li–O2 reactions but also benefits the catalytic efficiency of TTF. Meanwhile, TTF plays an important role in activating the Li2O2 passivated RuO2 catalysts and in helping RuO2 effectively oxidize the discharge products during charging. The synergetic effect of solid and liquid catalysts, beyond traditional bifunctional catalysis, obviously increases the cathodic kinetics and round-trip energy efficiency of LOBs

Synergetic Effect of Liquid and Solid Catalysts on the Energy Efficiency of Li–O₂ Batteries: Cell Performances and Operando STEM Observations

The sluggish cathodic kinetics and lower energy efficiency, associated with solid and insulating discharge products of Li2O2, are the key factors that prevent the practical implementation of Li–O2 batteries (LOBs). Here we demonstrate that the combination of the solid catalyst (RuO2) and soluble redox mediator tetrathiafulvalene (TTF) exhibits a synergetic effect in improving the cathodic kinetics and energy efficiency of LOBs by reducing both charge and discharge overpotentials. Operando electron microscopy observations and electrochemical measurements reveal that RuO2 not only exhibits bifunctional catalysis for Li–O2 reactions but also benefits the catalytic efficiency of TTF. Meanwhile, TTF plays an important role in activating the Li2O2 passivated RuO2 catalysts and in helping RuO2 effectively oxidize the discharge products during charging. The synergetic effect of solid and liquid catalysts, beyond traditional bifunctional catalysis, obviously increases the cathodic kinetics and round-trip energy efficiency of LOBs

Synergetic Effect of Liquid and Solid Catalysts on the Energy Efficiency of Li–O₂ Batteries: Cell Performances and Operando STEM Observations

The sluggish cathodic kinetics and lower energy efficiency, associated with solid and insulating discharge products of Li2O2, are the key factors that prevent the practical implementation of Li–O2 batteries (LOBs). Here we demonstrate that the combination of the solid catalyst (RuO2) and soluble redox mediator tetrathiafulvalene (TTF) exhibits a synergetic effect in improving the cathodic kinetics and energy efficiency of LOBs by reducing both charge and discharge overpotentials. Operando electron microscopy observations and electrochemical measurements reveal that RuO2 not only exhibits bifunctional catalysis for Li–O2 reactions but also benefits the catalytic efficiency of TTF. Meanwhile, TTF plays an important role in activating the Li2O2 passivated RuO2 catalysts and in helping RuO2 effectively oxidize the discharge products during charging. The synergetic effect of solid and liquid catalysts, beyond traditional bifunctional catalysis, obviously increases the cathodic kinetics and round-trip energy efficiency of LOBs

Synergetic Effect of Liquid and Solid Catalysts on the Energy Efficiency of Li–O₂ Batteries: Cell Performances and Operando STEM Observations

The sluggish cathodic kinetics and lower energy efficiency, associated with solid and insulating discharge products of Li2O2, are the key factors that prevent the practical implementation of Li–O2 batteries (LOBs). Here we demonstrate that the combination of the solid catalyst (RuO2) and soluble redox mediator tetrathiafulvalene (TTF) exhibits a synergetic effect in improving the cathodic kinetics and energy efficiency of LOBs by reducing both charge and discharge overpotentials. Operando electron microscopy observations and electrochemical measurements reveal that RuO2 not only exhibits bifunctional catalysis for Li–O2 reactions but also benefits the catalytic efficiency of TTF. Meanwhile, TTF plays an important role in activating the Li2O2 passivated RuO2 catalysts and in helping RuO2 effectively oxidize the discharge products during charging. The synergetic effect of solid and liquid catalysts, beyond traditional bifunctional catalysis, obviously increases the cathodic kinetics and round-trip energy efficiency of LOBs

Ultrastable Silicon Anode by Three-Dimensional Nanoarchitecture Design

State-of-the-art carbonaceous anodes are approaching their achievable performance limit in Li-ion batteries (LIBs). Silicon has been recognized as one of the most promising anodes for next-generation LIBs because of its advantageous specific capacity and secure working potential. However, the practical implementation of silicon anodes needs to overcome the challenges of substantial volume changes, intrinsic low conductivity, and unstable solid electrolyte interphase (SEI) films. Here, we report an inventive design of a sandwich N-doped graphene@Si@hybrid silicate anode with bicontinuous porous nanoarchitecture, which is expected to simultaneously conquer all these critical issues. In the ingeniously designed hybrid Si anode, the nanoporous N-doped graphene acts as a flexible and conductive support and the amorphous hybrid silicate coating enhances the robustness and suppleness of the electrode and facilitates the formation of stable SEI films. This binder-free and stackable hybrid electrode achieves excellent rate capability and cycling performance (817 mAh/g at 5 C for 10 000 cycles). Paired with LiFePO4 cathodes, more than 100 stable cycles can be readily realized in full batteries

Three-Dimensional Nanoporous Co₉S₄P₄ Pentlandite as a Bifunctional Electrocatalyst for Overall Neutral Water Splitting

Significant progress has recently been achieved in developing noble-metal-free catalysts for electrochemical water splitting in acidic and alkaline electrolytes. However, high-performance bifunctional catalysts toward both hydrogen evolution and oxygen oxidation reactions of neutral water have not been realized in spite of the technical importance for electrochemical hydrogen production in natural environments powered by renewable energy sources of wind, solar, and so on. Here, we report a nanoporous Co9S4P4 pentlandite with three-dimensional bicontinuous nanoporosity for electrochemical water splitting in neutral solutions. The three-dimensional binder-free catalyst shows a negligible onset overpotential, low Tafel slope, and excellent poisoning tolerance for hydrogen evolution reaction, comparable to or even better than commercial Pt catalysts. Remarkably, the new catalyst also has excellent catalytic activities toward oxygen evolution and, hence, can be used as both anode and cathode for overall neutral water splitting. These extraordinary catalytic activities toward neutral water splitting have never been obtained from non-noble-metal catalysts before. The bifunctional and low-cost catalyst holds great promise for practical applications in electrochemical water splitting in natural environments

Ultrastable Silicon Anode by Three-Dimensional Nanoarchitecture Design

State-of-the-art carbonaceous anodes are approaching their achievable performance limit in Li-ion batteries (LIBs). Silicon has been recognized as one of the most promising anodes for next-generation LIBs because of its advantageous specific capacity and secure working potential. However, the practical implementation of silicon anodes needs to overcome the challenges of substantial volume changes, intrinsic low conductivity, and unstable solid electrolyte interphase (SEI) films. Here, we report an inventive design of a sandwich N-doped graphene@Si@hybrid silicate anode with bicontinuous porous nanoarchitecture, which is expected to simultaneously conquer all these critical issues. In the ingeniously designed hybrid Si anode, the nanoporous N-doped graphene acts as a flexible and conductive support and the amorphous hybrid silicate coating enhances the robustness and suppleness of the electrode and facilitates the formation of stable SEI films. This binder-free and stackable hybrid electrode achieves excellent rate capability and cycling performance (817 mAh/g at 5 C for 10 000 cycles). Paired with LiFePO4 cathodes, more than 100 stable cycles can be readily realized in full batteries

A General Strategy for Engineering Single-Metal Sites on 3D Porous N, P Co-Doped Ti₃C₂T_X MXene

Two-dimensional (2D) MXenes have been developed to stabilize single atoms via various methods, such as vacancy reduction and heteroatom-mediated interactions. However, anchoring single atoms on 3D porous MXenes to further increase catalytic active sites and thus construct electrocatalysts with high activity and stability remains unexplored. Here, we reported a general synthetic strategy for engineering single-metal sites on 3D porous N, P codoped Ti3C2TX nanosheets. Through a “gelation-and-pyrolysis” process, a series of atomically dispersed metal catalysts (Pt, Ir, Ru, Pd, and Au) supported by N, P codoped Ti3C2TX nanosheets with 3D porous structure can be obtained and serve as efficient catalysts for the electrochemical hydrogen evolution reaction (HER). As a result of the favorable electronic and geometric structure of N­(O), P-coordinated metal atoms optimizing catalytic intermediates adsorption and 3D porous structure exposing the active surface sites and facilitating charge/mass transfer, the as-synthesized Pt SA-PNPM catalyst shows ∼20-fold higher activity than the commercial Pt/C catalyst for electrochemical HER over a wide pH range