Pt-based　nanoclusters　toward　the　hydrogen　evolution　reaction　(HER)　remain　the　most　promising　electrocatalysts.　However,　the　sluggish　alkaline　Volmer-step　kinetics　and　the　high-cost　have　hampered　progress　in　developing　high-performance　HER　catalysts.　Herein,　we　propose　to　construct　sub-nanometer　NiO　to　tune　the　d-orbital　electronic　structure　of　nanocluster-level　Pt　for　breaking　the　Volmer-step　limitation　and　reducing　the　Pt-loading.　Theoretical　simulations　firstly　suggest　that　electron　transfer　from　NiO　to　Pt　nanoclusters　could　downshift　the　Ed-band　of　Pt　and　result　in　the　well-optimized　adsorption/desorption　strength　of　the　hydrogen　intermediate　(H*),　therefore　accelerating　the　hydrogen　generation　rate.　NiO　and　Pt　nanoclusters　confined　into　the　inherent　pores　of　N-doped　carbon　derived　from　ZIF-8　(Pt/NiO/NPC)　were　designed　to　realize　the　structure　of　computational　prediction　and　boost　the　alkaline　hydrogen　evolution.　The　optimal　1.5%Pt/NiO/NPC　exhibited　an　excellent　HER　performance　and　stability　with　a　low　Tafel　slope　(only　22.5　mv　dec−1)　and　an　overpotential　of　25.2　mV　at　10　mA　cm−2.　Importantly,　the　1.5%Pt/NiO/NPC　possesses　a　mass　activity　of　17.37　A　mg−1　at　the　overpotential　of　20　mV,　over　54　times　higher　than　the　benchmark　20　wt%　Pt/C.　Furthermore,　DFT　calculations　illustrate　that　the　Volmer-step　could　be　accelerated　owing　to　the　high　OH−　attraction　of　NiO　nanoclusters,　leading　to　the　Pt　nanoclusters　exhibiting　a　balance　of　H*　adsorption　and　desorption　(ΔGH*　=　−0.082　eV).　Our　findings　provide　new　insights　into　breaking　the　water　dissociation　limit　of　Pt-based　catalysts　by　coupling　with　a　metal　oxide.　©　2023　The　Royal　Society　of　Chemistry.