Sustainable Electrosynthesis of Hexamethylenetetramine via Paired Electrolysis of Nitrate and PET Waste
Jingtao Zhou, Jiu Chen, Rui Shi, Zhengxiao Guo, Edmund C. M. Tse, Fulai Liu, Yong ChenABSTRACT
Hexamethylenetetramine (HMTA) is a critical organonitrogen compound widely used in the defense, pharmaceutical, and polymer industries. Conventional HMTA production relies on toxic formaldehyde (HCHO) and energy‐intensive Haber–Bosch‐derived ammonia (NH 3 ) as feedstocks. This study demonstrates a sustainable electrocatalytic approach for the direct synthesis of HMTA via paired electrolysis, using nitrate (NO 3 − ) and polyethylene terephthalate (PET) waste as nitrogen and carbon sources, respectively. With iron‐doped nickel phosphide (Fe–Ni 2 P) as a bifunctional catalyst, the system achieves concurrent cathodic NO 3 − reduction to NH 3 with a Faradaic efficiency of ∼ 96.0%, and anodic oxidation of PET‐derived ethylene glycol to electrophilic *HCHO intermediates. These resulting intermediates subsequently condense with nucleophilic NH 3 to form HMTA with ∼75.2% carbon selectivity. Mechanistic studies reveal that Fe doping induces charge redistribution and upshifts the d‐band center, thereby facilitating the adsorption and activation of reactants and lowering the energy barrier for *HCHO intermediate formation and desorption—a critical step enabling subsequent C─N coupling. This work establishes a mild and sustainable electrocatalytic route for HMTA synthesis from environmental waste, underscoring the potential of paired electrolysis in valorizing waste into valuable organonitrogen chemicals.