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.
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.
Enhancing the p‐orbital delocalization of a Bi catalyst (termed as POD‐Bi) via layer coupling of the short inter‐layer Bi−Bi bond facilitates the adsorption of intermediate *OCHO of CO2 and thus boosts the CO2 reduction reaction (CO2RR) rate to formate. X‐ray absorption fine spectroscopy shows that the POD‐Bi catalyst has a shortened inter‐layer bond after the catalysts are electrochemically reduced in situ from original BiOCl nanosheets. The catalyst on a glassy carbon electrode exhibits a record current density of 57 mA cm−2 (twice the state‐of‐the‐art catalyst) at −1.16 V vs. RHE with an excellent formate Faradic efficiency (FE) of 95 %. The catalyst has a record half‐cell formate power conversion efficiency of 79 % at a current density of 100 mA cm−2 with 93 % formate FE when applied in a flow‐cell system. The highest rate of the CO2RR production reported (391 mg h−1 cm2) was achieved at a current density of 500 mA cm−2 with formate FE of 91 % at high CO2 pressure.
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Developing efficient electrocatalysts for oxygen evolution reaction (OER) in pH‐neutral electrolyte is crucial for microbial electrolysis cells and electrochemical CO2 reduction. Unfortunately, the OER kinetics in neutral electrolyte is sluggish due to the low concentration of adsorbed reactants, with overpotentials of neutral OER at present much higher than that in acidic or alkaline electrolyte. Here, hydrated metal cations (Ca2+) are sought to be incorporated into the state‐of‐the‐art Ru–Ir binary oxide to tailor the surface oxygen environments (lattice‐oxygen and adsorbed oxygen species) for efficient neutral OER. Using a sol–gel method, ternary Ru–Ir–Ca oxides are synthesized in atomically homogenous manner, and the obtained catalyst on glassy carbon electrode achieves 10 mA cm−2 at a low overpotential of 250 mV, with no degradation for 200 h of operation. In situ X‐ray absorption spectroscopy, in situ 18O isotope‐labeling differential electrochemical mass spectrometry, and 18O isotope‐labeling secondary ion mass spectroscopy studies are carried out. The results reveal that incorporation of Ca2+ can enhance the covalency of metal–oxygen bonds and the electrophilic nature of surface metal‐bonded oxygen sites; and simultaneously facilitate the adsorption of water molecules on catalyst surface, which accelerates the lattice‐oxygen‐involved reaction, thus improving the overall OER performance of RuIrCaOx catalyst.
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