Hydrogen　production　by　photoelectrochemical　(PEC)　water　splitting　has　been　extensively　studied　on　copper　indium　sulfide　(CuInS2,　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　In2S3-supported　CIS　by　cyclic　voltammetry　(CV)　and　chronoamperometry　(CA).　The　Ni–In2S3/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–In2S3/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:　[Figure　not　available:　see　fulltext.]　©　2023,　The　Author(s),　under　exclusive　licence　to　Springer　Nature　B.V.