In this work, iron-doped nickel sulfides immobilized on reduced graphene oxide aerogel were synthesised by facile solvothermal and annealing methods. The obtained Fe–Ni–S/rGO composite with a 3D porous architecture provides a specific capacitance of 1220 F g⁻¹ at 1 A g⁻¹ with an excellent rate capability of 75.4% at 10 A g⁻¹, which is superior to bare nickel sulfide modified rGO (Ni–S/rGO). An asymmetric supercapacitor composed of the prepared Fe–Ni–S/rGO coupled with activated carbon exhibits an energy density of 30.5 Wh kg⁻¹ at a power density of 800 W kg⁻¹ with excellent cycling stability (82% capacitance retention after 10 000 cycles at 3 A g⁻¹), suggesting the practical application potential of the composite. DFT calculations indicate that the Fe dopants can modulate the electronic structure of the nickel sulfides by increasing the density of states near the Fermi level and narrowing the gap between the valence band and the conduction band, resulting in an improved charge transfer rate and hence charge storage capability of the composite. The excellent electrochemical properties of the composite suggest that doping transition metal atoms into the main lattice of the metal sulfides is an efficient way for designing electrodes for high performance supercapacitors.

中文翻译：

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锚定在还原氧化石墨烯上的铁掺杂硫化镍纳米球用于高性能超级电容器

在这项工作中，通过简便的溶剂热和退火方法合成了固定在还原氧化石墨烯气凝胶上的铁掺杂硫化镍。获得的具有3D多孔结构的Fe-Ni-S/rGO复合材料在1 A g ^{-1下提供了1220 F g -1}的比电容，在10 A g ^-1下具有75.4%的优异倍率性能，优于裸硫化镍改性 rGO (Ni–S/rGO)。由所制备的Fe-Ni-S/rGO与活性炭耦合组成的不对称超级电容器在800 W kg -1 的功率密度下表现出30.5 Wh kg -1 的能量密度，^并具有^优异的循环稳定性（10 000次后电容保持率为82%） 3 A g ^-1下的循环），表明该复合材料的实际应用潜力。DFT计算表明，Fe掺杂剂可以通过增加费米能级附近的态密度并缩小价带和导带之间的间隙来调节硫化镍的电子结构，从而提高电荷传输速率，从而提高电荷存储复合材料的能力。该复合材料优异的电化学性能表明，将过渡金属原子掺杂到金属硫化物的主晶格中是设计高性能超级电容器电极的有效方法。