Carbon dioxide (CO2) emissions are a major contributor to the global climate change. Strategies to reduce CO2 emissions are being considered. Among them, the carbon capture and sequestration (CCS) technology is being proposed as a viable approach for CO2 mitigation. However, this technology is suffered from high energy inputs and costs, making it economically challenging for widespread adoption. Developing efficient semiconductor-based photocatalysts that can harness solar energy appears to be a promising methodology to capture and recycle CO2 as a fuel feedstock. The conversion efficiency of these photocatalysts, however, is generally very low due to various limiting factors, such as fast electron-hole recombination rates, narrow light absorption range, and backward reactions. Thus, developing strategies to overcome the above limitations is an important task in this field.
Here we report a facile development of highly efficient and massively parallel (108 cm-2) copper oxide (CuO) nanowires coated with ultrathin zinc oxide (ZnO) layers by a few pulsed cycles of atomic layer deposition (ALD). The nanowires have a unique 1D structure with many discrete ZnO nano-islands coated on single crystalline CuO surface. The size and coverage of the ZnO islands could be easily tuned by varying the ALD cycles. These nanowires were subjected to UV–vis radiation-based CO2 photoreduction under saturated humidity conditions. The photocatalyst exhibits ultra-high CO2 conversion efficiency with a peak carbon monoxide (CO) yield of ~1.9 mmol/g-cat/hr. The materials combination of ZnO and CuO obviates the use of expensive and noble metal catalysts. The epitaxy observed between CuO nanowire and ZnO allows favorable and recombination-free electron transfer from the CuO nanowire to the ZnO. The island morphology of the ZnO creates exposed regions of both CuO and ZnO surfaces on the nanowires.