X-Ray Study of Niobium Disulfide Intercalated with Copper

Spontaneous self-intercalation of copper atoms into transition metal dichalcogenides

“…It revealed that some of Cu atoms were peeled off the surface of 2H-NbS 2 at this high temperature, until the atomic ratio drops to 0.6:1.0 (Cu:Nb). This theoretical maximum intercalant concentration is close to a previous experimental value obtained in high-temperature synthesis (18,19). The micrometer-scaled Cu powders self-assemble into nanostructures preceding the self-intercalation process when interacting with the TMDs.…”

“…S17), suggesting that a saturation of Cu intercalation state would be reached at this point. The homogeneous Cu 1.2 NbS 2 has a much higher intercalation state than the previous ones synthesized at high temperatures (16)(17)(18)(19)(20)(21). Our experimental saturation of Cu intercalation state is very close to that from the DFT calculations (table S1).…”

“…The observed expansion of d Nb-Nb upon Cu intercalation is much larger than that caused by intercalation of the preceding 3d transition metal atoms. For example, there is only expansion of d Nb-Nb = 0.037 and 0.016 nm for Mn 1/3 NbS 2 and Fe 1/3 NbS 2 , respectively (19). The intercalation compounds of Co 1/3 NbS 2 and Ni 1/3 NbS 2 show d Nb-Nb quite similar to those of pure 2H-NbS 2 (19).…”

“…S18). Accordingly, the neighboring Nb-Nb distance along the c axis (d Nb-Nb = c/2) increases from 0.597 nm for 2H-NbS 2 to 0.661 nm for Cu 1.2 NbS 2 , owing mainly to the expanding of interlayer spacing upon Cu intercalation since the sandwiched NbS 2 slab height only changes slightly (19,34). The swelling of d Nb-Nb leads to the gradual shift of (002) peak of Cu x NbS 2 to a lower diffraction angle until x = 1.2 upon which the diffraction peaks of Cu completely disappears (fig.…”

“…A large number of transition metal atoms could intercalate into group IV and V layered TMDs to form well-defined intercalation compounds, M′ x MX 2 (M′ is the intercalation metal different from the one in the host material, x intercalation state) (14,15). Most of them were synthesized by the solid-state reaction or chemical iodine-vapor transport (CVT) methods, both at the elevated temperatures (650° to 1100°C) (16)(17)(18)(19)(20)(21). This high-temperature solid or vapor phase reaction forms homogeneous intercalation compounds; however, some defects are introduced into TMDs hosts, and meanwhile, the process is energy and time intensive.…”