Liu Jinchao, Wang Yao, Liao Yifei, Wu Chaoling, Yan Yigang, Xie Haijiao, Chen Yungui
Department of Advanced Energy Materials, College of Materials Science and Engineering, Sichuan University, Chengdu 610065, P. R. China.
Engineering Research Center of Alternative Energy Materials & Devices, Ministry of Education, Chengdu 610065, P. R. China.
ACS Appl Mater Interfaces. 2021 Jun 16;13(23):26948-26959. doi: 10.1021/acsami.1c04325. Epub 2021 Jun 2.
Urea oxidation reaction (UOR) has been proposed to replace the formidable oxygen evolution reaction (OER) to reduce the energy consumption for producing hydrogen from electrolysis of water owing to its much lower thermodynamic oxidation potential compared to that of the OER. Therefore, exploring a highly efficient and stable hydrogen evolution and urea electrooxidation bifunctional catalyst is the key to achieve economical and efficient hydrogen production. In this paper, we report a heterostructured sulfide/phosphide catalyst (NiS-NiP/NF) synthesized via one-step thermal treatment of Ni(OH)/NF, which allows the simultaneous occurrence of phosphorization and sulfuration. The obtained NiS-NiP/NF catalyst shows a sheet structure with an average sheet thickness of ∼100 nm, and this sheet is composed of interconnected NiS and NiP nanoparticles (∼20 nm), between which there are a large number of accessible interfaces of NiS-NiP. Thus, the NiS-NiP/NF exhibits superior performance for both UOR and hydrogen evolution reaction (HER). For the overall urea-water electrolysis, to achieve current densities of 10 and 100 mA cm, cell voltage of only 1.43 and 1.65 V is required using this catalyst as both the anode and the cathode. Moreover, this catalyst also maintains fairly excellent stability after a long-term testing, indicating its potential for efficient and energy-saving hydrogen production. The theoretical calculation results show that the Ni atoms at the interface are the most efficient catalytically active site for the HER, and the free energy of hydrogen adsorption is closest to thermal neutrality, which is only 0.16 eV. A self-driven electron transfer at the interface, making the NiS sides become electron donating while NiP sides become electron withdrawing, may be the reason for the enhancement of the UOR activity. Therefore, this work shows an easy treatment for enhancing the catalytic activity of Ni-based materials to achieve high-efficiency urea-water electrolysis.
有人提出用尿素氧化反应（UOR）取代难以进行的析氧反应（OER），以降低水电解制氢的能耗，因为与OER相比，其热力学氧化电位要低得多。因此，探索一种高效稳定的析氢和尿素电氧化双功能催化剂是实现经济高效制氢的关键。在本文中，我们报道了一种通过对Ni(OH)/NF进行一步热处理合成的异质结构硫化物/磷化物催化剂（NiS-NiP/NF），该过程同时发生了磷化和硫化。所制备的NiS-NiP/NF催化剂呈现出片状结构，平均片层厚度约为100 nm，该片层由相互连接的NiS和NiP纳米颗粒（约20 nm）组成，两者之间存在大量可及的NiS-NiP界面。因此，NiS-NiP/NF在UOR和析氢反应（HER）中均表现出优异的性能。对于整体尿素-水电解，使用该催化剂作为阳极和阴极，要达到10和100 mA cm的电流密度，所需的电池电压仅为1.43和1.65 V。此外，经过长期测试，该催化剂仍保持相当优异的稳定性，表明其在高效节能制氢方面具有潜力。理论计算结果表明，界面处的Ni原子是HER最有效的催化活性位点，氢吸附自由能最接近热中性，仅为0.16 eV。界面处的自驱动电子转移使得NiS侧成为供电子体而NiP侧成为吸电子体，这可能是UOR活性增强的原因。因此，这项工作展示了一种简便的处理方法，可提高镍基材料的催化活性以实现高效尿素-水电解。
