Photo-catalytic reduction of CO$_{2}$ using Au--ZnO heterostructured nano-pyramids

Au-ZnO heterostructures were synthesized to create Au nanoparticles ($\sim$ 5 nm) attached to the basal surface of pyramid-shaped ZnO nanocrystals ($\sim$ 20 nm). The Au-ZnO heterostructures showed a large absorption peak around 521 nm which is assigned to the surface plasmon resonance of the Au nanoparticles. The photocatalytic activity of the Au-ZnO sample was evaluated inside a reaction cell purged with a 50 {\%} CO$_{2}$ and 50 {\%} H$_{2}$ gas mixture. The sample was then exposed to a 532 nm pulsed laser source to excite the plasmon resonance of Au and generate heat to drive the catalytic reaction of CO$_{2}$ and H$_{2}$ on the ZnO substrate. The primary products detected with gas chromatography were CO, CH$_{4}$ and C$_{2}$H$_{6}$. A maximum CO$_{2}$ conversion rate of 43.15 $\mu$ mol g$^{-1}$h$^{-1}$ was observed at the available highest laser power.