Shu Weihang, Sun Qi, Guo Mingrui
College of Chemistry and Chemical Engineering, Institute for Sustainable Energy and Resources, Qingdao University Qingdao 266071 Shandong P. R. China
RSC Adv. 2024 Aug 22;14(36):26659-26666. doi: 10.1039/d4ra04644g. eCollection 2024 Aug 16.
In traditional water electrolysis processes, the oxidation and reduction reactions of water are coupled in both time and space, which presents significant challenges. Here, we propose an optimized design for an electrochemical-chemical self-circulating decoupled system. This system uses the continuous Ni/Ni redox process on nickel hydroxide electrode sheets to stepwise couple the urea oxidation-assisted hydrogen production system, separating the hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) into two distinct steps: electrochemical and chemical reactions. In the first electrochemical step, water is reduced at the cathode to produce hydrogen, while the single-electron electrochemical oxidation of Ni(OH) at the anode generates NiOOH. Then, in the second chemical reaction step, NiOOH spontaneously oxidizes urea, causing its decomposition and simultaneously reducing back to the Ni(OH) state. We concurrently investigated the effects of temperature and OH-concentration on the spontaneous oxidation of urea. At 80 °C and with a 1 M KOH concentration containing 50 mg of urea solution, the NiOOH electrode successfully catalyzed the spontaneous decomposition of urea, achieving conversion rate of 100% and faradaic efficiency of 98%.
在传统水电解过程中，水的氧化和还原反应在时间和空间上都是耦合的，这带来了重大挑战。在此，我们提出了一种用于电化学-化学自循环解耦系统的优化设计。该系统利用氢氧化镍电极片上连续的镍/镍氧化还原过程逐步耦合尿素氧化辅助制氢系统，将析氢反应（HER）和尿素氧化反应（UOR）分离为两个不同的步骤：电化学反应和化学反应。在第一个电化学反应步骤中，水在阴极被还原以产生氢气，而镍（OH）在阳极的单电子电化学氧化生成氢氧化氧镍（NiOOH）。然后，在第二个化学反应步骤中，氢氧化氧镍自发氧化尿素，导致其分解并同时还原回氢氧化镍状态。我们同时研究了温度和氢氧根浓度对尿素自发氧化的影响。在80°C和含有50毫克尿素溶液的1 M氢氧化钾浓度下，氢氧化氧镍电极成功催化了尿素的自发分解，转化率达到100%，法拉第效率达到98%。
