Unravelling　the　influence　of　strain　and　geometric　effects　on　the　electrochemical　reduction　of　carbon　dioxide(CO2RR)on　Cu-based(or　Pd-based)alloys　remains　challenging　due　to　complex　local　microenvironment　variables.Herein,we　employ　two　PdCu　alloys(nanoparticles　and　nanodendrites)to　demonstrate　how　CO2RR　selectivity　can　shift　from　CO　to　HCOO-.Despite　sharing　consistent　phases,exposed　crystal　facets,and　overall　oxidative　states,these　alloys　exhibit　different　local　strain　profiles　due　to　their　distinct　geometries.By　integrating　experimental　data,in-situ　spectroscopy,and　density　functional　theory　calculations,we　revealed　that　CO2　prefers　adsorption　on　tensile-strained　areas　with　carbon-side　geometry,following　a*COOH-to-CO　pathway.Conversely,on　some　compressive-strained　regions　induced　by　the　dendrite-like　morphology,CO2　adopts　an　oxygen-side　geometry,favoring　an　*OCHO-to-HCOO　pathway　due　to　the　downshift　of　the　d-band　center.Notably,our　findings　elucidate　a　dominant　*OCHO-to-HCOO-pathway　in　catalysts　when　featuring　both　adsorption　geometries.This　research　provides　a　comprehensive　model　for　local　environment　of　bimetallic　alloys,and　establishes　a　clear　relationship　between　the　CO2RR　pathway　shift　and　variation　in　local　strain　environments　of　PdCu　alloys.