Department of Chemistry and Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva, 8410501, Israel.
Discipline of Chemistry, IIT Gandhinagar Palaj, Gandhinagr, 382355, Gujarat, India.
ChemSusChem. 2023 May 19;16(10):e202202271. doi: 10.1002/cssc.202202271. Epub 2023 Feb 1.
Electrolysis of water is a sustainable route to produce clean hydrogen. Full water-splitting requires a high applied potential, in part because of the pH-dependency of the H and O evolution reactions (HER and OER), which are proton-coupled electron transfer (PCET) reactions. Therefore, the minimum required potential will not change at different pHs. TEMPO [(2,2,6,6-tetramethyl-1-piperidin-1-yl)oxyl], a stable free-radical that undergoes fast electro-oxidation by a single-electron transfer (ET) process, is pH-independent. Here, we show that the combination of PCET and ET processes enables hydrogen production from water at low cell potentials below the theoretical value for full water-splitting by simple pH adjustment. As a case study, we combined the HER with the oxidation of benzylamine by anodically oxidized TEMPO. The pH-independent electrocatalytic oxidation of TEMPO permits the operation of a hybrid water-splitting cell that shows promise to perform at a low cell potential (≈1 V) and neutral pH conditions.
水的电解是生产清洁氢气的一种可持续途径。完全水分解需要施加高的外加电势，部分原因是 H 和 O 演化反应（HER 和 OER）的 pH 依赖性，这些反应是质子耦合电子转移（PCET）反应。因此，在不同 pH 值下，所需的最小电势不会改变。TEMPO（（2,2,6,6-四甲基-1-哌啶-1-基）氧自由基）是一种稳定的自由基，通过单电子转移（ET）过程快速发生电氧化，与 pH 无关。在这里，我们表明，通过简单的 pH 调节，PCET 和 ET 过程的结合可以在低于全水分解理论值的低电池电势下从水中生产氢气。作为一个案例研究，我们将 HER 与 TEMPO 阳极氧化的苄胺氧化结合起来。TEMPO 的 pH 无关的电催化氧化允许混合水分解电池的操作，该电池有望在低电池电势（≈1 V）和中性 pH 条件下运行。
