Achieving Efficient Electrocatalytic CO2-Involved N-Methylation on Cu–Ni–Al Heterostructured Catalysts

Using CO₂ as the carbon source for electrocatalytic C-N coupling with organic amino compounds to achieve N-methylation reactions offers an appealing route for synthesizing valuable N-containing chemicals, mitigating CO₂ emissions, and storing renewable energy but is challenging. Herein, we report the first work to design heterostructured Cu-Ni-Al electrocatalysts for N-methylation. Using 4-hydroxypiperidine (PD) as a substrate, high electrocatalytic performance with a 1-methyl-4-piperidinol (MPD) faradaic efficiency (FE) of 29.3%, a N-methylation selectivity of 100%, a C-selectivity of 78.3%, and a formation rate of 15.4 mmol g^-1 h^-1 was achieved in the H-cell. It also showed remarkable recycling stability. Control experiments and in situ measurements confirmed the key role of the CuO/NiAl₂O₄ heterostructure for the N-methylation reaction. Moreover, a combination of experimental and density functional theory (DFT) calculations demonstrated that CO₂ converted to the *H₂CO intermediate on the CuO/NiAl₂O₄ heterostructure, which underwent chemical condensation and subsequent reduction with nucleophilic amino compounds on the CuO/NiAl₂O₄ heterostructure, leading to high efficiency toward N-methylation. Further investigation showed that this system could also be extended to other amino compounds.