Ni(OH)2 and Co(OH)2 modified g-C3N4 for photocatalytic CO2 reduction

This study presents the synthesis and characterization of composite photocatalysts based on g- C 3 N 4 modified with Ni(OH) 2 and Co(OH) 2 for CO 2 reduction under visible light (λ = 410 nm). XRD, UV-Vis spectroscopy, and high-resolution TEM analyses revealed that the deposition of hydroxides did not disrupt the g-C 3 N 4 structure but caused a slight increase in the interlayer spacing and band gap; Ni(OH) 2 formed nanoparticles of ∼7 nm, whereas Co(OH) 2 crystallized as larger particles of ∼24 nm. TEM showed that after the photocatalytic CO 2 reduction, partial agglomeration of Ni(OH) 2 /NiO occurs. The catalyst containing 0.1 wt.% Ni(OH) 2 exhibited the highest activity – 7.04 μmol·g −1 ·h −1 , achieving a CO 2 reduction rate 1.9 times higher than that of pristine g-C 3 N 4 . The 0.5 wt.% Co(OH) 2 /g-C 3 N 4 photocatalyst was achieved a 1.3-fold increase in activity compared to pristine g-C 3 N 4 . This enhancement is attributed to the formation of a II type heterojunction between g-C 3 N 4 and Ni(OH) 2 , which facilitates charge transfer and suppresses recombination.