In
hydrogen production, the anodic oxygen evolution reaction (OER)
limits the energy conversion efficiency and also impacts stability
in proton-exchange membrane water electrolyzers. Widely used Ir-based
catalysts suffer from insufficient activity, while more active Ru-based
catalysts tend to dissolve under OER conditions. This has been associated
with the participation of lattice oxygen (lattice oxygen oxidation
mechanism (LOM)), which may lead to the collapse of the crystal structure
and accelerate the leaching of active Ru species, leading to low operating
stability. Here we develop Sr–Ru–Ir ternary oxide electrocatalysts
that achieve high OER activity and stability in acidic electrolyte.
The catalysts achieve an overpotential of 190 mV at 10 mA cm–2 and the overpotential remains below 225 mV following 1,500 h of
operation. X-ray absorption spectroscopy and 18O isotope-labeled
online mass spectroscopy studies reveal that the participation of
lattice oxygen during OER was suppressed by interactions in the Ru–O–Ir
local structure, offering a picture of how stability was improved.
The electronic structure of active Ru sites was modulated by Sr and
Ir, optimizing the binding energetics of OER oxo-intermediates.
The electrocatalytic urea oxidation reaction (UOR) provides more economic electrons than water oxidation for various renewable energy‐related systems owing to its lower thermodynamic barriers. However, it is limited by sluggish reaction kinetics, especially by CO2 desorption steps, masking its energetic advantage compared with water oxidation. Now, a lattice‐oxygen‐involved UOR mechanism on Ni4+ active sites is reported that has significantly faster reaction kinetics than the conventional UOR mechanisms. Combined DFT, 18O isotope‐labeling mass spectrometry, and in situ IR spectroscopy show that lattice oxygen is directly involved in transforming *CO to CO2 and accelerating the UOR rate. The resultant Ni4+ catalyst on a glassy carbon electrode exhibits a high current density (264 mA cm−2 at 1.6 V versus RHE), outperforming the state‐of‐the‐art catalysts, and the turnover frequency of Ni4+ active sites towards UOR is 5 times higher than that of Ni3+ active sites.
Rechargeable aqueous zinc‐ion batteries are attractive because of their inherent safety, low cost, and high energy density. However, viable cathode materials (such as vanadium oxides) suffer from strong Coulombic ion–lattice interactions with divalent Zn2+, thereby limiting stability when cycled at a high charge/discharge depth with high capacity. A synthetic strategy is reported for an oxygen‐deficient vanadium oxide cathode in which facilitated Zn2+ reaction kinetic enhance capacity and Zn2+ pathways for high reversibility. The benefits for the robust cathode are evident in its performance metrics; the aqueous Zn battery shows an unprecedented stability over 200 cycles with a high specific capacity of approximately 400 mAh g−1, achieving 95 % utilization of its theoretical capacity, and a long cycle life up to 2 000 cycles at a high cathode utilization efficiency of 67 %. This work opens up a new avenue for synthesis of novel cathode materials with an oxygen‐deficient structure for use in advanced batteries.
In electrochemical energy storage and conversion systems, the anodic oxygen evolution reaction (OER) accounts for a large proportion of the energy consumption. The electrocatalytic urea oxidation reaction (UOR) is one of the promising alternatives to OER, owing to its low thermodynamic potential. However, owing to the sluggish UOR kinetics, its potential in practical use has not been unlocked. Herein, we developed a tungsten‐doped nickel catalyst (Ni‐WOx) with superior activity towards UOR. The Ni‐WOx catalyst exhibited record fast reaction kinetics (440 mA cm−2 at 1.6 V versus reversible hydrogen electrode) and a high turnover frequency of 0.11 s−1, which is 4.8 times higher than that without W dopants. In further experiments, we found that the W dopant regulated the local charge distribution of Ni atoms, leading to the formation of Ni3+ sites with superior activity and thus accelerating the interfacial catalytic reaction. Moreover, when we integrated Ni‐WOx into a CO2 flow electrolyzer, the cell voltage is reduced to 2.16 V accompanying with ≈98 % Faradaic efficiency towards carbon monoxide.
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