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1. Dual hydrogen production from electrocatalytic water reduction coupled with formaldehyde oxidation via a copper-silver electrocatalyst

   https://doi.org/10.1038/s41467-023-36142-7  

   Li, Guodong ; Han, Guanqun ; Wang, Lu ; Cui, Xiaoyu ; Moehring, Nicole K. ; Kidambi, Piran R. ; Jiang, De-en ; Sun, Yujie ( January 2023 , Nature Communications)

   The broad employment of water electrolysis for hydrogen (H₂) production is restricted by its large voltage requirement and low energy conversion efficiency because of the sluggish oxygen evolution reaction (OER). Herein, we report a strategy to replace OER with a thermodynamically more favorable reaction, the partial oxidation of formaldehyde to formate under alkaline conditions, using a Cu₃Ag₇electrocatalyst. Such a strategy not only produces more valuable anodic product than O₂but also releases H₂at the anode with a small voltage input. Density functional theory studies indicate the H₂C(OH)O intermediate from formaldehyde hydration can be better stabilized on Cu₃Ag₇than on Cu or Ag, leading to a lower C-H cleavage barrier. A two-electrode electrolyzer employing an electrocatalyst of Cu₃Ag₇(+)||Ni₃N/Ni(–) can produce H₂at both anode and cathode simultaneously with an apparent 200% Faradaic efficiency, reaching a current density of 500 mA/cm²with a cell voltage of only 0.60 V.

    

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2. Stable Fe 2 P 2 S 6 Nanocrystal Catalyst for High‐Efficiency Water Electrolysis

   https://doi.org/10.1002/smtd.201900632  

   Chang, Jinfa ; Wang, Guanzhi ; Belharsa, Anas ; Ge, Junjie ; Xing, Wei ; Yang, Yang ( November 2019 , Small Methods)

   A crucial step toward clean hydrogen (H₂) energy production through water electrolysis is to develop high‐stability catalysts, which can be reliably used at high current densities for a long time. So far, platinum group metals (PGM) and their oxides, for example, Pt and iridium oxide (IrO₂) have been well‐regarded as the criterion for hydrogen and oxygen evolution reactions (HER and OER) electrocatalysts. However, the PGM catalysts usually undergo severe performance decay during the long‐term operation. Herein, the in situ growth of iron phosphosulfate (Fe₂P₂S₆) nanocrystals (NCs) catalysts on carbon paper synthesized by combing chemical vapor deposition with solvent‐thermal treatment is reported to show competitive performance and stability as compared to the state‐of‐the‐art PGM catalysts in a real water electrolyzer. A current density of 370 mA cm⁻²is achieved at 1.8 V when using Fe₂P₂S₆NCs as bifunctional catalysts in an anion exchange membrane water electrolyzer. The Fe₂P₂S₆NCs also show much better stability than the Pt‐IrO₂catalysts at 300 mA cm⁻²for a continuous 24 h test. The surface generated FeOOH on Fe₂P₂S₆is the real active site for OER. These results indicate that the Fe₂P₂S₆NCs potentially can be used to replace PGM catalysts for practical water electrolyzers.

    

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3. A Highly Active Star Decahedron Cu Nanocatalyst for Hydrocarbon Production at Low Overpotentials

   https://doi.org/10.1002/adma.201805405  

   Choi, Chungseok ; Cheng, Tao ; Flores Espinosa, Michelle ; Fei, Huilong ; Duan, Xiangfeng ; Goddard, III, William A. ; Huang, Yu ( December 2018 , Advanced Materials)

   The electrochemical carbon dioxide reduction reaction (CO₂RR) presents a viable approach to recycle CO₂gas into low carbon fuels. Thus, the development of highly active catalysts at low overpotential is desired for this reaction. Herein, a high‐yield synthesis of unique star decahedron Cu nanoparticles (SD‐Cu NPs) electrocatalysts, displaying twin boundaries (TBs) and multiple stacking faults, which lead to low overpotentials for methane (CH₄) and high efficiency for ethylene (C₂H₄) production, is reported. Particularly, SD‐Cu NPs show an onset potential for CH₄production lower by 0.149 V than commercial Cu NPs. More impressively, SD‐Cu NPs demonstrate a faradaic efficiency of 52.43% ± 2.72% for C₂H₄production at −0.993 ± 0.0129 V. The results demonstrate that the surface stacking faults and twin defects increase CO binding energy, leading to the enhanced CO₂RR performance on SD‐Cu NPs.

    

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4. Discovery of LaAlO3 as an efficient catalyst for two-electron water electrolysis towards hydrogen peroxide

   https://doi.org/10.1038/s41467-022-34884-4  

   Baek, Jihyun ; Jin, Qiu ; Johnson, Nathan Scott ; Jiang, Yue ; Ning, Rui ; Mehta, Apurva ; Siahrostami, Samira ; Zheng, Xiaolin ( November 2022 , Nature Communications)

   Electrochemical two-electron water oxidation reaction (2e-WOR) has drawn significant attention as a promising process to achieve the continuous on-site production of hydrogen peroxide (H₂O₂). However, compared to the cathodic H₂O₂generation, the anodic 2e-WOR is more challenging to establish catalysts due to the severe oxidizing environment. In this study, we combine density functional theory (DFT) calculations with experiments to discover a stable and efficient perovskite catalyst for the anodic 2e-WOR. Our theoretical screening efforts identify LaAlO₃perovskite as a stable, active, and selective candidate for catalyzing 2e-WOR. Our experimental results verify that LaAlO₃achieves an overpotential of 510 mV at 10 mA cm⁻²in 4 M K₂CO₃/KHCO₃, lower than those of many reported metal oxide catalysts. In addition, LaAlO₃maintains a stable H₂O₂Faradaic efficiency with only a 3% decrease after 3 h at 2.7 V vs. RHE. This computation-experiment synergistic approach introduces another effective direction to discover promising catalysts for the harsh anodic 2e-WOR towards H₂O₂.

    

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5. 2D Copper Tetrahydroxyquinone Conductive Metal–Organic Framework for Selective CO 2 Electrocatalysis at Low Overpotentials

   https://doi.org/10.1002/adma.202004393  

   Majidi, Leily ; Ahmadiparidari, Alireza ; Shan, Nannan ; Misal, Saurabh N. ; Kumar, Khagesh ; Huang, Zhehao ; Rastegar, Sina ; Hemmat, Zahra ; Zou, Xiaodong ; Zapol, Peter ; et al ( February 2021 , Advanced Materials)

   Metal–organic frameworks (MOFs) are promising materials for electrocatalysis; however, lack of electrical conductivity in the majority of existing MOFs limits their effective utilization in the field. Herein, an excellent catalytic activity of a 2D copper (Cu)‐based conductive MOF, copper tetrahydroxyquinone (CuTHQ), is reported for aqueous CO₂reduction reaction (CO₂RR) at low overpotentials. It is revealed that CuTHQ nanoflakes (NFs) with an average lateral size of 140 nm exhibit a negligible overpotential of 16 mV for the activation of this reaction, a high current density of ≈173 mA cm⁻²at −0.45 V versus RHE, an average Faradaic efficiency (F.E.) of ≈91% toward CO production, and a remarkable turnover frequency as high as ≈20.82 s⁻¹. In the low overpotential range, the obtained CO formation current density is more than 35 and 25 times higher compared to state‐of‐the‐art MOF and MOF‐derived catalysts, respectively. The operando Cu K‐edge X‐ray absorption near edge spectroscopy and density functional theory calculations reveal the existence of reduced Cu (Cu⁺) during CO₂RR which reversibly returns to Cu²⁺after the reaction. The outstanding CO₂catalytic functionality of conductive MOFs (c‐MOFs) can open a way toward high‐energy‐density electrochemical systems.

    

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