Preparation of Nano-flower-shaped Carbon Loaded Ag-ZnO Using Lignin Template Method and Its Photocatalytic CO₂ Conversion

Using lignin(AL) as a template, nanoscale lignin-loaded zinc oxide(ZnO/AL) composite materials were prepared. Silver nanoparticles(AgNPs) were loaded onto this base material, and a nano-flower-shaped carbon loaded silver-zinc oxide(Ag-ZnO/C) composite material was prepared through high-temperature calcination. The composite materials were characterized using scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), and X-ray photoelectron spectroscopy(XPS), and their ability for photocatalytic conversion of CO₂ was evaluated. The research results showed that when using lignin as a template, ZnO/AL could maintain the nano-flower morphology and structure during the subsequent calcination processes, and lignin could reduce silver ions in situ to AgNPs, uniformly loading them on the ZnO petal layers. Energy-dispersive X-ray spectroscopy(EDX) results showed that Ag-ZnO/C composite material was mainly composed of C(14.7%), O(14.4%), Zn(34.1%) and Ag(18.0%) elements. Combined with TEM, XRD, and XPS analysis, the successful preparation of the Ag-ZnO/C composite material was confirmed. The ability of photocatalytic CO₂ conversion of the composite materials with different Ag⁺/Zn²⁺ ratios of 1∶2(Ag_0.1-ZnO_0.2/C) and 1∶10(Ag_0.1-ZnO_1.0/C) was compared. Photocurrent response and impedance spectroscopy test results indicated that Ag_0.1-ZnO_1.0/C had higher photocurrent intensity, lower resistance, and superior photocatalytic activity. The photocatalytic CO₂ conversion by Ag_0.1-ZnO_1.0/C showed consistently low CH₄ production, and the CO yield could reach 114.9 μmol/g after 10 hours of reaction.