(131i) Catalysis for a Sustainable Future: Processes Development, Reactor Design, and Novel Materials Systems for Electrochemical Energy Conversion and Storage

Recently, there has been an extraordinary push for the development of new energy technologies toward a more sustainable and green economy. Despite this, the world’s reliance on fossil fuels is likely to continue until alternative solutions become economically viable. It is essential to create methods for generating energy—or energy carriers—from renewable sources and to convert this energy into useful work with maximum efficiency and minimal environmental impact. To that effect, our research focuses on designing and developing catalysts and catalytic systems and processes that can help change the energy landscape for a sustainable future. More specifically, our research directions are three fold as follows: (1) Developing and preparing novel nanostructures as well as deep fundamental understanding of their formation mechanism and surface chemistry, (2) Investigating their catalytic activity, selectivity, and durability from the materials’ level as well as the interfacial microenvironment as defined by the reaction chemistry and conditions, electrolyte nature, reactor design, among others, and (3) Advanced characterization methods (both in situ and ex situ) to probe the catalysts as well as the MEAs evolution and degradation mechanism under various reactions conditions. In what follows is a showcase demonstrating our effort in designing and fabricating integrated seawater electrolyzer with H2-Cl2 fuel cell for marine carbon dioxide removal.

Marine carbon dioxide removal (mCDR) has emerged as a promising strategy for greenhouse gas removal (GHG-R) to support global net-zero emission targets and mitigate climate change. We present an mCDR approach that integrates seawater electrolyzer with a H₂- Cl₂ fuel cell to achieve ocean de-acidification via CO₂ capture, while supplying renewable electricity by converting the Cl₂ byproduct back to the power grid. This system offers several advantages: (a) increases CO₂ ocean update, while generating natural carbonate minerals for marine ecosystem recovery and production of precursors for carbon-neutral cement, (b) Cl₂ and H₂ byproducts from seawater electrolysis are used to power fuel cell, which generates electricity to support renewable energy grid.

In this work, we designed a seawater-resilient electrolyzer operated by robust, non-leaching catalysts compatible with marine environments. For chlorine evolution reaction (CER), we synthesized RuTiO_x dimensionally stable anode (DSA) with various Ru/Ti ratio following solid state sintering method. In DI water, our zero-gap proton exchange membrane (PEM) electrolyzer recorded a cell potential of 1.7 V at current density (j) = 250 mA/cm². Using seawater feeds, the total cell potential increased to 2.7 V at the same j value. The potential difference is attributed to the combination of HER and CER from seawater along with the energy required for pH swing in the anolyte and catholyte. For long term stability, the electrolyzer was then operated at 250 mA/cm² for >70 h. The resulting products of chlorine in the anolyte and sodium hydroxide in the catholyte were quantified. Selectivity toward CER is characterized by using electrochemical mass spectrometry (EC-MS), demonstrating the catalysts selectivity > 90. Techno-economic analysis of our zero-gap showed that capturing a ton CO2 per day would yield an overall potential profit of > $800,000 after taking into consideration all capital and operating costs. This suggests that the electrolysis products themselves can jump start an enormous mineral extraction industry from the ocean to pay for carbon capture. This work establishes the foundation for developing a scalable, renewable-energy-driven, environmentally friendly, and cost-effective system for mCDR.