Efficient CO2 electroreduction on Pd-based core-shell nanostructure with tensile strain

•Core-shell nanocatalysts are fabricated to study the strain effect on CO2 reduction.•The catalytic performance follows the trend of Au@Pd > Pd > AuCu@Pd.•The catalytic activity is positively related to the tensile strain effect.•The increased tensile strain with thinner shell thickness enhances catalytic activity.