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 mgcat-1) nearly 7-fold higher than that of the conventional unmodified Cu single-atom catalyst (Cu1-N2, 0.73 mg h-1 mgcat-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.