Integrated dual-confinement effects of quantum dots and spatial CO2 activation for enhanced photoreduction performance

Abstract

CO2 photoreduction represents a sustainable strategy for mitigating carbon emissions and producing renewable fuels. However, the overall efficiency of this process is fundamentally depressed by the lack of cooperative regulation between charge separation and CO2 activation. To address this challenge, a dual-confinement photocatalytic system composed of Co3S4 quantum dots (QDs) and NiAl-layered double hydroxide (LDH) nanosheets is rationally designed. The quantum confinement of Co3S4 QDs produces discrete energy levels and enables localized accumulation of photogenerated electrons, while the spatial confinement of NiAl-LDH provides hydroxyl-rich surfaces that facilitate CO2 adsorption and intermediate stabilization. The strong electronic interaction establishes an interfacial electric field, which promotes directional electron transfer and forms an electron-rich interfacial domain for CO2 activation. Photoelectrochemical analyses confirm that the dual confinement remarkably accelerates charge separation and prolongs carrier lifetimes. In-situ DRIFTS and density functional theory calculations further demonstrate that the accumulated electrons at the confined interface strongly couple with adsorbed CO2 molecules, enabling efficient electron injection into anti-bonding orbitals and lowering the formation barrier of COOH* intermediates. Consequently, the optimized sample of CSL-6 achieves a CO generation rate of 31.2 μmol•g-1•h-1 and an apparent quantum efficiency of 0.89% at 420 nm, which are approximately 17.8 times and 11.6 times higher than those of the pure NiAl-LDH and Co3S4 QDs, respectively. This study elucidates how dual confinement synchronizes charge migration and surface reaction steps through a coupled electronic–chemical mechanism, providing a mechanistic foundation and design principle for high-efficiency CO2 photoreduction catalysts.