低能耗半电解水全反应分步制氢气和氧气

Hydrogen gas produced from electrolysis of water can not only be fuels, but also applied to fuel cells to produce electricity, which works with smart grid to serve the so called “hydrogen economy”. Nowadays, diaphragms or membranes are used in electrolysis of water. The drawbacks of the present electrolysis of water are low electrolysis rate, permeation of hydrogen and oxygen via diaphragms, high cost of membranes and high electrolysis voltage. Half electrolysis as a new concept can run one desirable faradaic redox half reaction at a reaction electrode with the aid of a supercapacitor electrode. In this process, the other unwanted faradaic redox half reaction is eliminated, which can reduce the electrical energy consumption. In this project, the half electrolysis concept is applied to electrolysis of water using a two-electrode cell comprising one supercapacitor electrode and the other reaction electrode in aqueous solution as an electrolyte. When charging the supercapacitor electrode, hydrogen evolution would occur at the reaction electrode as a negative electrode. When discharging supercapacitor electrode, oxygen evolution would occur at the reaction electrode as a positive electrode. The half electrolysis of water would realize the whole reaction of electrolysis of water by stepwise producing hydrogen and oxygen gases without diaphragms or membranes. Therefore, the half electrolysis of water can prevent the gas permeation, reduce the cost of the whole instrument, increase the electrolysis rate and reduce the energy consumption of electrolysis. This project aims at verifying the scientific principle and technical feasibility of the course of stepwise producing hydrogen and oxygen gases in the instrument of the half electrolysis of water. The research contents include the material selection, preparation and designation of the supercapacitor and reaction electrodes, the voltage in the half electrolysis of water and its mechanism, and the influence of electrolyzer configuration on the half electrolysis of water.

电解水产生的氢气既可用作燃料，又可用于燃料电池产生电，与智能电网一道形成氢经济。现在使用的电解水技术都需使用隔膜，存在电解速率低、气体易混合、隔膜成本高、电解电压高等缺点。全新的半电解概念依靠超级电容电极辅助，在一个反应电极上仅仅发生需要的半反应，消除不需要的半反应，能降低电解能耗。本项目将半电解概念引入电解水，用水溶液作电解液，用电容电极和反应电极构成两电极电解池。对电容电极充电时（正极），反应电极（负极）制氢气；对电容电极放电时（负极），反应电极（正极）制氧气。半电解水将分步实现制氢气和氧气的全反应，无需隔膜。因此，半电解水能避免气体混合、降低装置成本、提高电解速率、降低电解能耗。本项目旨在验证半电解水装置分步制氢气和氧气过程的科学原理和技术可行性，研究涉及电容电极和反应电极的材料筛选、制备与匹配设计、半电解水电解电压及机理和电解池结构对半电解水的影响。

电解水产生的氢气既可用作燃料，又可用于燃料电池产生电，与智能电网一道形成氢经济。现在使用的电解水技术都需使用隔膜，存在电解速率低、气体易混合、隔膜成本高、电解电压高等缺点。本项目采用半电解水实现连续、分步制氢气和氧气的全反应，无需隔膜，解决了气体混合，降低了电解能耗。在酸性、中性和碱性盐水电解液中，半电解依靠超级电容电极辅助，在一个反应电极上仅仅发生氢气和氧气逸出的半反应。对电容电极充电时，反应电极制氢气；对电容电极放电时，反应电极制氧气。在碱性海水电解液中，相比传统电解水，半电解水无需石棉隔膜，用相同的商业电容电极和铂线电极制氢气和氧气，无氯气生成，能节省14%的电能。用纳米铂碳电极替换铂线电极，制氢气和氧气的法拉第效率为98.0%和96.3%。在电容电极的优化方面，发展了一步分子级活化法制备活性炭，用低温裂解法制备出碳纳米点/石墨烯柔性膜。以柚子皮为前驱体通过一步分子级活化法制备的活性炭的产率为16.7%，在碱性水系电解液中的比电容为219 F/g。碳纳米点/石墨烯柔性膜在酸性水系电解液中的比电容为266 F/g。它们的比电容均高于商业活性炭YP50f。通过半电解水以及优化超级电容电极，本项目实现了分步制氢气和氧气的全反应，减少了隔膜成本，降低了能耗。