Pyrolysis-Controlled Engineering of Nickel–Nitrogen–Carbon Catalytic Sites on Carbon Supports for Robust and Selective CO₂ Electroreduction to CO

Electrocatalytic carbon dioxide reduction (CO2RR) to carbon monoxide (CO) represents a sustainable pathway for closing the carbon cycle. In this study, polymerized nickel phthalocyanine (NiPPc) was employed as a molecular precursor and immobilized onto a highly conductive Ketjenblack (KB) carbon support through ultrasonic-assisted deposition, forming a NiPPc-KB composite catalyst. The carbon–nitrogen coordination environment was systematically tailored by controlled annealing to optimize the catalytic performance. The resulting Ni-NC/KB-T catalyst series exhibited exceptional selectivity for CO production during CO2RR. Electrochemical evaluations revealed that the Ni-NC/KB-800 catalyst achieved a CO Faradaic efficiency exceeding 90% across a broad potential window (−0.7 to −1.2 V, V vs RHE), with peak performance at −1.1 V (FECO = 99%, JCO = −42.2 mA cm–2). Notably, the catalyst demonstrated robust durability during a 14-h chronoamperometric test, maintaining >94% CO selectivity throughout the stability assessment. This work establishes a rational strategy for engineering efficient Ni-NxCy catalytic sites through the pyrolysis-controlled optimization of molecular precursors on carbon supports, providing insights for designing high-performance CO2RR electrocatalysts.