Influences of Na+ co-cation on the structure and performance of Cu/SSZ-13 selective catalytic reduction catalysts

•Na+ addition promotes low temperature turnover rates of Cu/SSZ-13 catalysts.•Na+ addition adversely influences dispersion of isolated Cu-ions.•Na+ addition adversely influences catalyst hydrothermal stability at high Cu loadings.•Co-cation addition to Cu/SSZ-13 can be used in practical SCR catalysts, however care must be taken to control the extents.•Discussions on quantification of isolated Cu-ions with EPR and H2-TPR.