Rational design of bifunctional hydroxide/sulfide heterostructured catalyst for efficient electrochemical seawater splitting

Heterostructure engineering is one of the most promising strategies for efficient water splitting by electrocatalysts. However, it remains challenging to design heterostructured catalysts to achieve the desired goals in both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in seawater splitting. Here, particulate heterostructures of FeCoNi hydroxide/sulfide supported on nickel foams were prepared by hydrothermal methods to achieve a high-performance bifunctional catalyst. The synthesized FeCoNi hydroxide/sulfide exhibited excellent electrocatalytic performance, requiring an overpotential of 195 mV for OER and 76 mV for HER to achieve a current density of 10 mA cm^-2 while showing excellent stability. The catalyst maintains its excellent performance even in artificial or natural seawater with high salinity, which is a harsh environment. When applied directly to a water splitting system, the catalyst achieves a current density of 10 mA cm^-2 at only 1.5 V (1.57 V in alkaline seawater). The FeCoNi hydroxide/sulfide heterostructure is an excellent electrocatalytic bifunctional catalyst due to compositional modulation, systematic charge transfer optimization, improved intermediates adsorption, and increased electrocatalytic active sites and the synergistic effect of the heterostructure.

Heterostructure and doping dual strategies engineering of MoS1.5Se0.5@VS2 nanosheets aggregated nano-roses for super sodium-ion batteries

Herein, selenium (Se)-doped MoS_1.5Se_0.5@VS₂ nanosheets aggregated nano-roses were successfully prepared from a simple hydrothermal process and the subsequent selenium doping process. The hetero-interfaces between MoS_1.5Se_0.5 and VS₂ phase can effectively promote the charge transfer. Meanwhile, the different redox potentials of MoS_1.5Se_0.5 and VS₂ alleviate volume expansion during the repeated sodiation/desodiation processes, which improves the electrochemical reaction kinetics and structural stability of electrode material. Besides, Se doping can induce charge reconstruction and improve the conductivity of electrode materials, resulting in improved diffusion reaction kinetics by expanding interlayer spacing and exposing more active sites. When used as anode material for sodium ion batteries (SIBs), the MoS_1.5Se_0.5@VS₂ heterostructure exhibits excellent rate capability and long-term cycling stability with the capacity of 533.9 mAh g^-1 at 0.5 A g^-1 and a reversible capacity of 424.5 mAh g^-1 after 1000 cycles at 5 A g^-1, demonstrating potential application as anode material for SIBs.