Effect of cyclic voltammetry on the deposition of Ni cocatalyst on CuInS 2 photoelectrode for water splitting under solar light irradiation

Hydrogen production by photoelectrochemical (PEC) water splitting has been extensively studied on copper indium sulfide (CuInS 2 , CIS) photoelectrodes. In the hydrogen evolution reaction (HER), nickel species were investigated as an alternative cocatalyst to platinum from the viewpoint of elemental strategy: Ni cocatalyst was deposited on In 2 S 3 -supported CIS by cyclic voltammetry (CV) and chronoamperometry (CA). The Ni–In 2 S 3 /CIS photoelectrode consisted of metallic Ni covered with Ni(OH) 2 as a passivation layer. Furthermore, the particle size of Ni species could be changed by the degree of reduction and oxidation reaction, suppressing particle size increase. The Ni–In 2 S 3 /CIS photoelectrode fabricated by the CV exhibited higher PEC performance than that by the CA at a constant potential. These results clearly show that CV is an effective method for depositing relatively uniform and small Ni particles, which strongly affects the efficiency of PEC water splitting. Graphical abstract