Effect of Trivalent Metal Cations in Layered Double Perovskites on Highly Selective CO2 Photoreduction to CO

Trivalent metal cation engineering in vacancy-ordered layered double perovskites (LDP) is a useful strategy to tune photocatalytic activity. However, the regulatory mechanism of cation composition on photocatalytic performance still lacks in-depth understanding. This study explores vacancy-ordered LDP with the formula Cs4CdX2Cl12 (X = Bi, Sb) for photocatalytic CO2 reduction. The catalytic performance is fine-tuned by regulating the composition of M(III)-site metal ions. The yields of CO and CH4 from Cs4CdSb2Cl12 MCs were measured at 23.81 and 2.68 μmol g-1, resulting in a CO selectivity of 89.9%. Cs4CdBi2Cl12 demonstrated higher yields, with CO and CH4 produced at 90.77 and 2.53 μmol g-1, achieving a CO selectivity of 97.2%. In addition, in situ diffuse reflectance infrared Fourier transform spectra reveal that the modulation of metal ions at the M(III)-position can enhance the photocatalytic activity of Cs4CdX2Cl12 (X = Bi, Sb) MCs. Density functional theory (DFT) analysis suggests that Bi displays a lower energy barrier than Sb for the rate-determining step, thus facilitating the effective photocatalytic reduction of CO2 to CO. These findings highlight the influence of metal cation selection on structural properties and catalytic performance.