The　structure　and　morphology　of　oxide　on　the　metal　electrodes　are　strongly　linked　with　the　activity　and　stability　of　the　electrocatalysts.　Herein,　the　novel　co-effect　of　anion　and　hydrated　proton　on　structure　of　PtO2　formation　is　observed　during　the　oxidation　of　water　on　Pt(100)　preferentially　oriented　nanoparticles　with　in　situ　Raman　spectroscopy　and　XPS.　Higher　concentrations　(≥1.5　M)　of　non-specifically　adsorbed　perchlorate　in　0.1　M　perchloric　acid　solution　facilitated　the　formation　of　crystalline　α−PtO2　during　the　electro−oxidation　of　Pt(100),　and　no　crystalline　α−PtO2　was　obtained　without　acid.　Higher　acidity　electrolyte　solution　favors　the　formation　of　crystalline　α–PtO2,　indicating　that　proton　plays　a　key　role　since　specifically　adsorbed　sulfate　without　sulfuric　acid　did　not　lead　to　the　formation　of　crystalline　α–PtO2.　A　model　containing　anions,　protons,　and　water　molecules　co-adsorbed　on　the　Pt　surface　is　constructed　during　density　functional　theory　(DFT)　calculations,　which　well　explains　the　formation　of　crystalline　α–PtO2　depending　on　anion　and　proton.　The　study　findings　provide　an　alternate　approach　for　environmentally　friendly　and　controllable　preparation　of　Adams’　catalyst　and　an　atomic–level　understanding　of　oxide　formation　on　Pt　electrodes,　which　is　essential　for　developing　the　next–generation　electro-catalyst　with　exceptional　performance　and　stability.　©　2024　Elsevier　B.V.