image: Schematic illustration of H-type PEM-ECMR with PEM separator and Ti-based membrane anode (Left); Photo of the tubular Co3O4/Ti membrane electrode (Middle); SEM images of the Co3O4 nanoarrays (Right). view more
Credit: ©Science China Press
This study is led by Prof. Zhen Yin (College of Chemical Engineering and Materials Science, Tianjin University of Science and Technology), Prof. Jianxin Li (State Key Laboratory of Separation Membranes and Membrane Processes, Tiangong University) and Prof. Ding Ma (College of Chemistry and Molecular Engineering, Peking University).
A robust electrochemical strategy with efficient and stable membrane anode (Co3O4 NNs/Ti membrane electrode) constructed with Co3O4 nanoneedle arrays (Co3O4 NNs) and the titanium membrane for the electrochemical oxidation of refractory organic pollutants and simultaneous production of high-purity hydrogen over the cathode in wastewater under the neutral condition. The membrane electrodes with 3D array nanostructures were constructed via the assembly of 1D structures consisting of small Co3O4 nanoparticles (NPs) and anchored on the membrane surface via an in-situ growth process without binders and additives, which substantially facilitated the electrochemical reactions. The 3D nanoarray of Co3O4 could dramatically enhance the intimate interfacial adhesion with substrates, and thus facilitate the electron transport and charge transfer at the interface of electrode and electrolyte, leading to abundant catalytic active sites. The diffusion/mass transfer limitation for traditional plate electrodes was overcome via the loading of 3D nanoarray on the surface of membrane pore and the flow-through configuration.
The Co3O4 NNs/Ti membrane electrode in a flow-through mode exhibited superior decontamination efficiency and excellent stability for wastewater treatment during the EAOP. A finite element numerical method via the COMSOL Multiphysics was employed to investigate the surface electric field distribution of membrane electrodes with different catalytic nanostructures. Meanwhile, in situ Raman experiments were performed in Na2SO4 solution to understand the catalytic sites of Co3O4 NNs/Ti membrane electrode under an electric field. The degradation mechanism of phenol with the Co3O4 NNs/Ti membrane electrode was also discussed according to the analyses of permeate solution. Finally, in order to produce high-purity hydrogen, we designed a H-type ECMR (PEM-ECMR) with Nafion membrane as separator and the Co3O4 NNs/Ti anode, demonstrating superior degradation performances for phenol and dye water, stable pure hydrogen production and excellent long-term stability. The present work demonstrates that the PEM-ECMR cell is flexible and practical for decentralized wastewater treatment and pure hydrogen production under a low electric field.
“It would be a promising alternative route for simultaneous clean fresh water recovery and sustainable hydrogen energy production, whose energy cost can be further reduced if it powered with renewable energy in the future, such as solar energy. Moreover, the wastewater from industrial effluents can be used as hydrogen source via water electrocatalysis combined with pollutant electrooxidation process” Zhen says.
This work will inspire further development of electrochemical processes, modular decentralized water treatment systems, and technological advancements for the treatment of contaminated water in parallel with renewable energy production in the future.
See the article:
Yin, Z., Zhang, K., Ma. N. et al. Catalytic membrane electrode with Co3O4 nanoarrays for simultaneous recovery of water and hydrogen from wastewater, Sci. China Mater. (2022). https://doi.org/10.1007/s40843-022-2168-y.
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Science China Materials