**4. Factors affecting composite co-electroplating**

#### **4.1. Deposition current density**

The deposition rate in electrodeposition process plays a vital role in the fabrication of nano‐ composites. The number density of particles approaching the cathode surface depends on the applied electric potential, and the thickness of the growing metal is determined by the deposition current density. The rate determining step in the co-electrodeposition is when the strong adsorption of particles on the cathode surface occurs. A strong adsorption of particles is always difficult and is improved by applying current or feeding the corresponding overpo‐ tential in the electrolyte. As a consequence, the particle incorporation in the coating increases continuously. However, at a sufficiently high current density, the codeposition rate of the coating decreases drastically. This may be caused by the limited supply of the metal ions toward cathode leading to the decrease in the particle amount.[54] The embedded particle density as a function of current density has been studied for different particle concentrations in the bath in Ref. [55]. It has been reported that at lower current densities (0.5 A dm-2), the embedded particle density is poor due to a weaker adsorption of nanoparticles on the cathode. In few reports, there is a negligible effect of current density on the particle density in the matrix. [42, 56] In other cases, various optimum particle concentrations have been detected in the current density versus particle concentration graph.[51, 57–59] It is also noteworthy point that the current density not only influences the codeposition rate, but the particles present in the electrolyte also modify the current density and hence the morphology of the deposits.[60, 61]
