Photoelectrochemical CO2 conversion with tunable semiconductor nanostructures

利用太阳能将二氧化碳（CO2）转化为有价值的化学物质是实现可持续碳循环的一种有吸引力的方式，可以减少我们社会对化石燃料的依赖和温室气体的排放。一个很有前景的概念是“人工光合作用”，它将吸收阳光和催化成分结合在一个仅由阳光、水和二氧化碳提供动力的综合系统中。然而，实际实施受到催化二氧化碳转化的复杂性的阻碍，催化二氧化碳转化遵循多步骤，能源密集型反应导致各种可能的产品。我们的目标是使用可调模型系统来更深入地了解相关半导体-电解质过程的多层相互作用及其对能量转换效率和产物选择性的影响。我们使用光电化学方法，为精确的研究提供必要的控制。我们的关键创新是使用有序（In,Ga）N纳米线阵列作为光电极，具有明确的，可调节的性质（组成，掺杂，形态），影响光收集和电催化行为。我们将研究纳米尺度形态（纳米线长度和直径，阵列几何形状）如何通过影响传输过程来影响催化选择性，以及增强光吸收。我们还将分析半导体电子结构的调谐，特别是导带边缘，如何通过改变反应的热力学驱动力来影响产物的选择性。由于光电化学方法允许通过调节光强度来控制反应速率，我们可以独特地将热力学和动力学效应解耦，从而能够系统地研究影响光电化学CO2转化的复杂相互作用。这些结果将为开发高效和可扩展的太阳能驱动可再生化学合成集成系统提供有价值的见解。

The use of solar energy to convert carbon dioxide (CO2) into valuable chemicals is an attractive way towards a sustainable carbon cycle that reduces our society's fossil fuel dependence and greenhouse gas emissions. One promising concept is "artificial photosynthesis", which combines sunlight-absorbing and catalytic components in an integrated system powered only by sunlight, water and CO2. However, practical implementation is hampered by the complexity of catalytic CO2 conversion which follows multi-step, energy-intensive reactions leading to various possible products. Our goal is to use a tunable model system to gain a deeper understanding of the multilayered interaction of the relevant semiconductor–electrolyte processes and their influence on energy conversion efficiency and product selectivity.We use a photoelectrochemical approach that provides the control necessary for precise studies. Our key innovation is the use of ordered (In,Ga)N nanowire arrays as photoelectrodes with well-defined, adjustable properties (composition, doping, morphology) which affect both light harvesting and electrocatalytic behaviors. We will study how nanoscale morphology (nanowire length and diameter, array geometry) can influence catalytic selectivity by affecting transport processes, as well as enhance light absorption. We will additionally analyze how tuning of the semiconductor electronic structure, particularly the conduction band edge, may affect the product selectivity through varying the thermodynamic driving force for the reaction. Since the photoelectrochemical approach allows control over the reaction rate by modulating the light intensity, we can uniquely decouple thermodynamic and kinetic effects to enable systematic investigation of the complex interplay influencing photoelectrochemical CO2 conversion. These results will provide valuable insights for the development of efficient and scalable integrated systems for sunlight-driven renewable chemical synthesis.