Informed by results from the Ni-Cu system (Figure ) and theoretical calculations (Figure ), we expand our study to consider the role of TM electronic structure (work function and Ed vs EF ) and H * affinity (H chemisorption energy ) on NO3RR FE and selectivity to ammonium. We focus our discussion on potentials with nominal competition between HER and NO3RR (-0.4, -0.5, and -0.6 VRHE; Figures and), with data for additional potentials provided as Supplementary Figures and and Supplementary Table .