Anchoring Pd single atoms through S vacancies of defective nickel–sulfur for efficient electrocatalytic polyethylene terephthalate oxidation coupled with hydrogen evolution

Abstract

Electrocatalytically upgrading polyethylene terephthalate (PET) plastic waste into valuable chemicals is deemed a promising avenue that meets the requirements of sustainable development. Rational fabrication of efficient single-atom catalysts is highly desired, and seeking adequate matrixes to anchor single atoms with strong metal–support interaction is important in improving catalytic performance. Herein, Pd single atoms are precisely anchored into S vacancies of defective Ni₃S₂ (d-Ni₃S₂) to synthesize Pd/d-Ni₃S₂ via a stepwise hydrothermal–photoreduction method. The Pd/d-Ni₃S₂ exhibits superior electrocatalytic performance toward ethylene glycol (EG) oxidation to formic acid (FA), with high selectivity (94.3%) and Faraday efficiency (95.6%). Further operando characterizations (Raman, infrared, and electrochemical impedance spectroscopies) and DFT calculations disclose that the introduction of Pd single atoms promotes the structure reconstruction of d-Ni₃S₂, along with the adsorption of optimized reactants and diminished energy barriers of the rate-determining step, consequently resulting in enhanced electrocatalytic performance. Furthermore, a membrane-electrode assembly (MEA) flow cell system is constructed to couple anode PET hydrolysate oxidation with cathode hydrogen evolution, providing a green and energy-saving approach for PET waste upcycling and simultaneous hydrogen production.