One-step hydrothermal synthesis of Cu0/P2Mo18/CF tandem catalytic electrode for electrocatalytic nitrate to Ammonia conversion

Electrochemical nitrate reduction reaction (eNO 3 RR) technology offers a sustainable approach for ammonia synthesis due to its high efficiency and environmental compatibility. However, the complex multi-electron reduction process limits catalytic activity and selectivity. Herein, a tandem catalytic system is designed to address this challenge. A Cu 0 /P 2 Mo 18 /CF composite electrode, featuring copper (Cu) nanoparticle- modified P 2 Mo 18 nanocolumns, was prepared via one-step hydrothermal synthesis. The as-fabricated electrode delivers outstanding electrocatalytic performance toward eNO 3 RR. At a potential of −0.7 V vs. RHE, the nitrate (NO 3 − ) removal efficiency and ammonia (NH 3 ) selectivity reach 99% and 91%, respectively, alongside a high NH 3 yield of 666.6 μg·h −1 ·cm −2 . Moreover, the electrode retains superior catalytic activity and stability after 30 consecutive cyclic tests. The superior performance stems from the cascade effect between Cu 0 /Cu + on copper nanoparticles and P 2 Mo 18 . Cu 0 /Cu + facilitates rapid NO 3 − adsorption and reduction to nitrite (NO 2 − ), while electron-rich [P 2 Mo 18 O 62 ] 6− and acidic sites selectively reduce intermediates to NH 3 . In situ characterization further reveals that the reaction pathway proceeds as follows: *NO 3 −  → *NO 2 −  → *NO→*N → *NH → *NH 2  → *NH 3 . This work establishes a polyoxometalate-based cascade catalytic system, providing a novel strategy for designing efficient electrocatalysts for selective nitrate-to-ammonia conversion.