One-Step Strategy to Maximize Single-Atom Catalyst Utilization in Nitrate Reduction via Bidirectional Optimization of Mass Transfer and Electron Supply

Single-atom catalysts offer exceptional performance but face practical challenges due to complex synthesis and low efficiency caused by mass transfer resistance. In this study, based on a simple one-step pyrolysis method, we designed a Cu single-atom catalyst with high active site exposure and a locally electron-deficient environment (HE Cu₁-N₄) to achieve maximum utilization efficiency in electrocatalytic nitrate reduction (NO₃RR). Using advanced characterization techniques, we confirmed that its unique 3D structure enhances Cu atom exposure and reduces nitrate (NO₃^-) mass transfer resistance. Synchrotron radiation and DFT calculations showed that adjusting the coordination environment induces a local electron-deficient effect in Cu atoms, increasing the electrostatic attraction to NO₃^-. HE Cu₁-N₄ achieved 100% NH₃ selectivity across a wide range of NO₃^- concentrations, with an NH₃ yield (5.09 mg h^-1 mg_cat^-1) nearly 7-fold higher than that of the conventional unmodified Cu single-atom catalyst (Cu₁-N₂, 0.73 mg h^-1 mg_cat^-1). Under pilot-scale conditions, HE Cu₁-N₄ demonstrated strong resistance to interference and excellent stability in complex water systems. A simple modification method enhanced the utilization efficiency of single atoms in single-atom catalysts, significantly improving the catalytic activity of the material. Moreover, this straightforward synthesis strategy holds promise for the large-scale production of single-atom catalysts, paving the way for practical engineering applications.