Electrochemical Engineering for Carbon Conversion and Biosensing

Carbon dioxide (CO2) is the primary greenhouse gas emitted through human activities. In 2019, CO2 accounts for over 80 percent of U.S. greenhouse emissions. It has been a consensus that, the accumulation of greenhouse gases is directly related to global warming, an effect that causes irregular rise in average global temperature. Without intervention, the ever-rising temperature will cause a series of cascaded events, which eventually leads to increased draught, more severe storms, rising ocean level, loss of lands and species etc. To curb the global warming, there is a pressing need for new technologies to slow down the carbon emissions. The electroreduction of CO2 (CO2RR), once scaled, seems to be promising solution to reduce the CO2 emission from human activities. Products such as carbon monoxide (CO), ethylene, ethanol and n-propanol can be produced from an electrolyzer, with CO2 and water as feedstock. Even though such device needs to be powered by electricity, when coupled with renewable energy source, the device itself can be zero-emission and the electricity price can be averaged down over the long-term of use. Once the profit generated from the sales of products break-evens with the electricity price, the CO2RR will be self-sustainable and operated without government subsidies. The rest is to scale up and offset the global emission. There are two major challenges in CO2RR technology, scalability and efficiency. To scale-up, the device needs to accomplish certain metrices, including current densities, durability etc. Many engineering optimizations have been done to address the scalability concerns. In this dissertation, we will see examples such as flow-type cells, catalyst nano-engineering, electrolyte engineering and their impact on scalability. Another challenge comes with the energy efficiency, which depends on factors like overpotential, selectivity, counter reactions etc. In an ideal world, 100% of the electrons should be used for producing the target product, at lowest possible voltage. To achieve this, we have designed product-specific catalysts, such as 4H-Au nanoribbons for CO, Cu nanocubes for ethylene, Cu nanowires for ethanol and Cu1@C3N4 (a single atom catalyst) for acetate. Each catalyst shows competitive selectivity and activity for the target product at the time of publication. The fight against climate change is far from over. It’s a fight of the century and a fight by all of us. Our endeavor for the past few years might inspire others in this research field to develop the next generation CO2RR device. But more importantly, I hope our work can encourage more researchers to join this field to advance together