Redox Flow Batteries using Carbon Dioxide; from electrocatalysis to cell engineering

人们普遍认为，减少二氧化碳排放、清洁能源生产及其储存是21世纪最严峻的技术挑战之一。大规模采用许多清洁能源技术的一个主要缺点是能源生产周期的间歇性(峰谷对比)，需要高效的储能设备。电化学技术在清洁能源的产生和储存(如各种电池、燃料电池和超级电容器)和将二氧化碳转化为有用的化学品(通过电还原)方面都得到了深入的研究。本发现研究计划首次将这两个先前分离的领域统一在申请人发明的基于负极上的二氧化碳/甲酸(或甲酸盐阴离子)氧化还原对的新型氧化还原液流电池技术中。在使用可再生能源的电池充电过程中，二氧化碳被还原为甲酸(或甲酸盐阴离子，取决于pH值)，作为能量存储介质。在正极上，采用了液流电池中常用的氧化还原电偶(例如，溴-溴)。在电池放电循环中，电能是通过反转反应产生的(例如，在负极，甲酸被氧化回二氧化碳)。二氧化碳/甲酸-溴/溴氧化还原液流电池在298K时的理论比能量密度为每公斤反应物547Wh。这种方法如果成功，可以提供工业二氧化碳排放器(如燃煤发电厂、水泥和钢铁制造厂等)。采用碳中性能源发电和储存技术，同时减少向大气排放的二氧化碳。换句话说，这是一种将二氧化碳废物转化为能源的新方法。

Mitigation of carbon dioxide emissions, clean energy generation and its storage are widely recognized as among the most stringent technological challenges of the twenty first century. A major drawback for large scale adoption of many clean energy technologies is the intermittent nature of the energy generation cycle (peak vs. off-peak) requiring efficient energy storage devices. Electrochemical technologies are intensely investigated for both clean energy generation and storage (e.g., various batteries, fuel cells and supercapacitors) and CO2 conversion to useful chemicals (by electro-reduction). The present discovery research program proposes to unite for the first time these two previously separate fields in a novel redox flow battery technology invented by the applicant based on the CO2 / formic acid (or formate anion) redox couple at the negative electrode. During battery charging using renewable energy source, CO2 is reduced to formic acid (or formate anion, depending on pH), which acts as energy storage medium. At the positive electrode, a redox couple commonly used in flow batteries (e.g., bromide – bromine) is employed. In the battery discharge cycle electric power is produced by reversing the reactions (e.g., at the negative electrode formic acid is oxidized back to CO2). The theoretical specific energy density of the carbon dioxide/formic acid – bromide/bromine redox flow battery is 547 Wh per kg of reactants at 298 K. This approach, if successful, could provide industrial CO2 emitters (e.g., coal fired power plants, cement and steel manufacturing plants etc.) with a carbon-neutral energy generation and storage technology, while reducing the CO2 emitted to the atmosphere. In other words, it is a novel approach for conversion of CO2 waste to energy.