Cu-doped Co3O4-coated Ti3C2 MXene composite for effective photoelectrochemical CO2 reduction

Since the Industrial Revolution, global CO2 emissions have steadily increased, surpassing 420 ppmv and worsening global warming. This study addresses the urgent need for CO2 removal and reuse by developing a heterogeneous system combining copper-doped cobalt oxide (Cu-doped Co3O4) and titanium carbide (Ti3C2 MXene) for photocatalytic CO2 reduction to formic acid (HCOOH). The proposed mechanism involves CO2 interacting with the catalyst to form an *OCHO state, which then yields HCOOH. This process utilizes hydrothermal synthesis and self-assembly, with structural analysis through XRD, XPS, SEM, and UV-Vis. The Cu doping enhances charge separation in the Co3O4 semiconductor, while MXene improves hydrophilicity and reaction efficiency. Optimally, a 15% MXene and 6% Cu concentration achieved a formic acid production rate of 1.85 mmol·h⁻¹·g⁻¹ under simulated sunlight, indicating the composite's potential in photocatalytic CO2 reduction and sustainable energy applications.