• Energy Research

It is critical and challenging to develop high performance transition metal phosphides (TMPs) electrocatalysts for oxygen evolution reaction (OER) to address fossil energy shortages. Herein, we report the synthesis of Co2P embedded in N-doped porous carbon (Co2P@N-C) via a facile one-step strategy. The obtained catalyst exhibits a lower overpotential of 352 mV for OER at a current density of 10 mA cm−2 and a small Tafel slope of 84.6 mV dec−1, with long-time reliable stability. The excellent electrocatalytic performance of Co2P@N-C can be mainly owed to the synergistic effect between the Co2P and highly conductive N-C substrate, which not only affords rich exposed active sites but also promotes faster charge transfer, thus significantly promoting OER process. This work presents a promising and industrially applicable synthetic strategy for the rational design of high performance nonnoble metal electrocatalysts with enhanced OER performance.

Lithium-ion batteries are still the main theme of the contemporary market. Commercial graphite has struggled to meet the demand of high energy density for various electronic products due to its low theoretical capacity. Therefore, exploring for a new anode with high capacity is important. Vanadium nitride has attracted widespread attention due to its high theoretical specific capacity and good chemical/thermal stability. However, vanadium nitride is accompanied by huge volume expansion and nanoparticle agglomeration during the electrochemical reaction, which limits its application. Herein, sea-urchin-like vanadium nitride (SUK-VN) was successfully prepared with a simple hydrothermal method combined with an annealing strategy to boost the actual capacity of the vanadium nitride. The special sea-urchin-like morphology effectively suppresses the agglomeration of vanadium nitride nanoparticles and exposes more reactive sites, which facilitates the electrochemical performance of electrode materials. In the half-cells, sea-urchin-like vanadium nitride exhibits a specific capacity of 361.5 mAh g−1 at 0.1 A g−1 after 60 cycles, and even still achieves a specific capacity of 164.5 with a Coulomb efficiency of approximately 99.9% at 1 A g−1 after 500 cycles. Such a strategy provides the potential to enhance the electrochemical properties of vanadium nitride anodes in terms of solving the nanoparticle agglomeration.

Single-atom catalysts (SACs) within carbon matrix became one of the most promising alternatives to noble metal-based catalysts for oxygen reduction reaction (ORR). Although SACs have significant benefits in reducing the total catalyst cost, it also has the disadvantages of weak interaction between atoms and poor stability. Hence, there is still much room for improvement for the catalyst activity. In response, we designed a Fe-Co-Pt ternary metal single atom catalyst anchored on covalent organic framework (COF)-derived N-doped carbon nanospheres (Pt, Fe, Co/N-C). Due to effective charge transfer between Pt single atom and neighboring Fe-Co components, an intense electron interaction can be established within the Pt, Fe, Co/N-C catalyst. This is beneficial for enhancing charge transfer efficiency, modulating d electronic structure of Pt center and weakening oxygen intermediate adsorption, thus distinctly accelerating ORR catalytic kinetics. As expected, the half-wave potential of Pt, Fe, Co/N-C was 0.845 V, much higher than those of commercial 20 wt% Pt/C (0.835 V), Pt/N-C (0.79 V) and Fe, Co/N-C (0.81 V) counterparts. Moreover, the Pt, Fe, Co/N-C catalyst demonstrated much-improved cycling stability and methanol tolerance.

Aqueous zinc-ion batteries are considered one of the promising large-scale energy storage devices of the future because of their high energy density, simple preparation process, efficient and safe discharge process, abundant zinc reserves, and low cost. However, the development of cathode materials with high capacity and stable structure has become one of the key elements to further development of aqueous zinc-ion batteries. Vanadium-based compounds, as one of the cathode materials for aqueous zinc-ion batteries, have various structures and high reversible capacities. Among them, vanadium-based sulfides have higher academic ability, better electrochemical activity, lower ion diffusion potential barrier, and a faster ion diffusion rate. As a result, vanadium-based sulfides have received extensive attention and research. In this review, we summarize the recent progress of vanadium-based sulfides applied in aqueous zinc-ion batteries, highlighting their effective strategies for designing optimized electrochemical performance and the underlying electrochemical mechanisms. Finally, an overview is provided of current vanadium-based sulfides and their prospects, and other perspectives on vanadium-based sulfide cathode materials for aqueous zinc-ion batteries are also discussed.

Lithium-ion batteries (LIBs) have already gained significant attention because they have satisfactory energy density and no memory effect, making them one of the most widely used energy storage systems. In commercial LIBs, graphite is widely used as an anode material due to its excellent electrical conductivity and structural stability; however, as they are limited by their restricted theoretical capacity, there is an urgent need for the development of novel anode materials for LIBs. For this purpose, we designed a nitrogen-doped two-dimensional layered porous carbon material (2D-PNC) based on a covalent organic framework (COF) generated by a Schiff base reaction as a precursor. The characterization analysis results show that 2D-PNC is made of stacked two-dimensional ultra-thin carbon sheets with a porous structure. This unique structure is beneficial for electrolyte impregnation and lithium-ion storage, resulting in excellent electrochemical performance of 2D-PNC, which shows a high specific capacity of 573 mAh g−1 after 380 cycles at 0.5 A g−1. The results show that 2D-PNC provides the possibility of a practical application of high-performance lithium-ion batteries.