Although　aqueous　synthesis　of　nanocrystals　is　advantageous　in　terms　of　the　cost,　convenience,　environmental　friendliness,　and　surface　cleanness　of　the　product,　nanocrystals　of　Pt　and　non-noble　metal　alloys　are　difficult　to　obtain　with　controlled　morphology　and　composition　from　this　synthesis　owing　to　a　huge　gap　between　the　reduction　potentials　of　respective　metal　salts.　This　huge　gap　could　now　be　remedied　by　introducing　a　sulfite　into　the　aqueous　synthesis,　which　is　believed　to　resemble　an　electroless　plating　mechanism,　giving　rise　to　a　colloid　of　Pt-M　(M=Ni,　Co,　Fe)　alloy　nanowires　with　an　ultrasmall　thickness　(ca.　2.6　nm)　in　a　high　yield.　The　sulfite　also　leads　to　the　formation　of　surface　M-S　bonds　and　thus　atomic-level　Pt/M-S(OH)　interfaces　for　greatly　boosted　hydrogen　evolution　kinetics　under　alkaline　conditions.　An　activity　of　75.3　mA　cm(-2)　has　been　achieved　with　3　mu　g　of　Pt　in　1　M　KOH　at　an　overpotential　of　70　mV,　which　is　superior　to　previously　reported　catalysts.