Toward an Understanding of the Enhanced CO₂ Electroreduction in NaCl Electrolyte over CoPc Molecule‐Implanted Graphitic Carbon Nitride Catalyst

Abstract Direct CO₂ electrolysis in seawater enables the simultaneous conversion of CO₂ into CO and the chlorine ions into Cl₂, further meeting downstream industry needs such as phosgene synthesis and also facilitating the net consumption of CO₂. As a result, the direct implementation of CO₂ electrolysis in seawater is urgently required. Herein, a CoPc molecule‐implanted graphitic carbon nitride nanosheets (CoPc/g‐C₃N₄) electrocatalyst is prepared via a simple mechanochemistry method. The CoPc/g‐C₃N₄ with a negatively charged surface and preferential adsorption capability for Na⁺ can achieve appreciable faradaic efficiency (FE, 89.5%) toward CO with a current density of 16.0 mA cm⁻² in natural seawater and also realize long‐term operation for 25 h in simulated seawater. Process monitoring further reveals that the chlorine ions in NaCl electrolyte can modulate the reaction microenvironment around the anode, which in turn has positive effects on the CO₂RR in cathode. The CO₂RR overall splitting in the simulated seawater exhibits a maximum FE of 98.1% towards CO at cell voltage of 3 V. This work describes the development of a carbon‐coupled CoPc molecular catalyst that can drive the CO₂ electrolysis in simulated seawater and provides a promising and energy‐saving coupled reaction system for direct coproduction of CO and Cl₂.