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-<i>T</i> 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 (FE_CO = 99%, <i>J</i>_CO = -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.