Reasonable construction of high activity and selectivity electrocatalysts is crucial to achieve efficient ethanol oxidation reaction (EOR). However, the oxidation of ethanol tends to produce CO species that poison the active centers of the EOR electrocatalysts. Herein, a unique amorphous CrO x -protected defect-rich ultrafine Pd nanowires (CrO x -Pd NWs) is developed. On the one hand, the CrO x layer can act as a protective layer to maintain the structure of the nanowire. On the other hand, it can play the role of OH regulator to optimize the adsorption energy barrier of intermediate species in Pd nanowire, thereby enhancing the ability of the catalyst to resist CO poisoning. The CrO x -Pd NWs exhibit excellent EOR performance with 3.64 times higher mass activity and 50 mV lower CO electro-oxidation potential than commercial Pd black. The results show that the CrO x layer promotes the dissociation of H 2 O into OH ads , while the CrO x transfers electrons to neighboring Pd atoms optimizing the electronic configuration of Pd, thus selectively oxidizing ethanol to acetate and preventing the formation of toxic * CO. This work provides an effective strategy for the synthesis of nanowire materials with oxide/metal interfaces and offers new ideas for the design of catalysts that can efficiently drive EOR.
Acidic Cr(VI)-containing wastewater has received increasing attention in recent years. Schwertmannite is a suitable adsorbent for its acid resistance and good adsorption ability. However, it shows poor Cr(VI) adsorption performance under acidic conditions. Herein, inspired by the fast neutralization-mineralization process of acid mine drainage (AMD) triggered by alkaline rocks, a novel nano-scaled schwertmannite (Sch-2.7) with high Cr(VI) adsorption capacity was synthesized at constant pH of 2.7 via adding OH − . Compared with common schwertmannite (Sch), appropriate OH − effectively improved mineral yield (the precipitation efficiency of Fe: 96.75% vs. 29.93%), specific surface area (65.1 m 2 /g vs. 18.9 m 2 /g), surface group content, and further Cr(VI) adsorption ability of Sch-2.7. The maximum adsorption capacity was 54.17 (pH = 3), 61.59 (pH = 4), and 66.5 mg/g (pH = 5) for Sch-2.7, whereas only 20.35, 24.51, and 27.17 mg/g for Sch. On average, the former was 2.53 times higher than the latter. Temperature and coexisting ions had little influences on the sorption process of Sch-2.7. The mechanism analysis demonstrated that the Cr(VI) removal by Sch-2.7 was a more thermodynamic favorable process due to abundant reactive-active components on Sch-2.7 for adsorption reaction. This work provided new insight into performance optimization and application potential on Cr(VI) removal of schwertmannite.
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