Gao Xintong, Bai Xiaowan, Wang Pengtang, Jiao Yan, Davey Kenneth, Zheng Yao, Qiao Shi-Zhang
School of Chemical Engineering, The University of Adelaide, Adelaide, SA, Australia.
Nat Commun. 2023 Sep 20;14(1):5842. doi: 10.1038/s41467-023-41588-w.
Renewable energy-based electrocatalytic oxidation of organic nucleophiles (e.g.methanol, urea, and amine) are more thermodynamically favourable and, economically attractive to replace conventional pure water electrooxidation in electrolyser to produce hydrogen. However, it is challenging due to the competitive oxygen evolution reaction under a high current density (e.g., >300 mA cm), which reduces the anode electrocatalyst's activity and stability. Herein, taking lower energy cost urea electrooxidation reaction as the model reaction, we developed oxyanion-engineered Nickel catalysts to inhibit competing oxygen evolution reaction during urea oxidation reaction, achieving an ultrahigh 323.4 mA cm current density at 1.65 V with 99.3 ± 0.4% selectivity of N-products. In situ spectra studies reveal that such in situ generated oxyanions not only inhibit OH adsorption and guarantee high coverage of urea reactant on active sites to avoid oxygen evolution reaction, but also accelerate urea's C - N bond cleavage to form CNO intermediates for facilitating urea oxidation reaction. Accordingly, a comprehensive mechanism for competitive adsorption behaviour between OH and urea to boost urea electrooxidation and dynamic change of Ni active sites during urea oxidation reaction was proposed. This work presents a feasible route for high-efficiency urea electrooxidation reaction and even various electrooxidation reactions in practical applications.
基于可再生能源的有机亲核试剂(如甲醇、尿素和胺)的电催化氧化在热力学上更有利,并且在经济上更具吸引力,有望取代电解槽中传统的纯水电氧化来制氢。然而,由于在高电流密度(例如,>300 mA cm)下存在竞争性析氧反应,这降低了阳极电催化剂的活性和稳定性,因此具有挑战性。在此,以低成本尿素电氧化反应为模型反应,我们开发了氧阴离子工程化的镍催化剂,以抑制尿素氧化反应过程中的竞争性析氧反应,在1.65 V时实现了323.4 mA cm的超高电流密度,N产物的选择性为99.3±0.4%。原位光谱研究表明,这种原位生成的氧阴离子不仅抑制OH吸附,保证尿素反应物在活性位点上的高覆盖率以避免析氧反应,而且加速尿素的C-N键断裂形成CNO中间体以促进尿素氧化反应。据此,提出了OH与尿素之间竞争性吸附行为促进尿素电氧化以及尿素氧化反应过程中镍活性位点动态变化的综合机理。这项工作为实际应用中的高效尿素电氧化反应乃至各种电氧化反应提供了一条可行的途径。