The electrochemical urea oxidation (UOR) involves the generation of gases bubbles, which often cause the blockage of the electrode surface leading to decline activity. Herein, we report the growth of Ni 5 P 4 nanosheets on nickel foam as bifunctional electrode (CA-Ni 5 P 4 @NiO x /NF) for urea electrolysis. The results indicated that a thin layer of amorphous NiOx formed on the surface of Ni 5 P 4 nanosheets to yield a unique crystalline@amorphous core–shell structure, which can be maintained during long time urea electrolysis. The outstanding UOR performance of CA-Ni 5 P 4 @NiO x /NF was attributed to the unique structure, which not only combine the good conductivity and abundant active sites, but also rendered the CA-Ni 5 P 4 @NiO x /NF superhydrophilic and aerophobic that significantly facilities the release of gases bubbles formed during UOR to avoid the blockage of the active sites. As a result, the CA-Ni 5 P 4 @NiO x /NF electrode exhibited excellent performance for UOR, which only needs 1.45 V (vs. RHE) to deliver a current of 100 mA/cm 2 . When used as anode for direct urea fuel cell (DUFC), it could reach a maximal power density as high as 3.4 mW/cm 2 with an OCV of 0.76 V. The CA-Ni 5 P 4 @NiO x /NF also exhibited excellent activity for hydrogen evolution reaction (HER), with -0.089 V (vs. RHE) to deliver a current of 10 mA/cm 2 . The electrolyzer constructed with CA-Ni 5 P 4 @NiO x as both anode and cathode could run for more than 10 h at a high current load about 100 mA/cm 2 without appreciable potential change, indicating the superb stability of the CA-Ni 5 P 4 @NiO x electrode. Our work provides new insights for understanding as well as the development of advanced electrode for DUFC and urea electrolysis.
Rational design of efficient catalysts with high activity and prolonged stability to overcome the sluggish kinetics of electrocatalytic water splitting is imperative but challenging. The optimization of electrocatalysts’ components and geometric structure is deemed an effective strategy. Herein, Fe, Co co-doped Ni5P4 hierarchical cube-on-sheet nanoarrays grown on coal-based carbon nanofibers (FeCo-Ni5P4@C–CNFs) was synthesized by electrospinning, hydrothermal methods, coprecipitation, and phosphorization. Benefiting from metal doping with a strong interaction for electron transfer, the cube-on-sheet architecture with excellent superhydrophilic and aerophobic properties for mass transportation, and self-supported C–CNFs as a conductive substrate with remarkable structural durability, the obtained FeCo-Ni5P4@C–CNFs displays superior bifunctional electrocatalytic properties. In 1.0 M KOH electrolyte, the overpotentials of hydrogen evolution and oxygen evolution reactions are only 46 and 221 mV at a current density of 10 mA cm–2, respectively. In addition, the assembled FeCo-Ni5P4@C–CNFs electrolyzer requires a low cell voltage of 1.50 V at 10 mA cm–2. This study offers a method for the rational design of highly active electrocatalysts and also enriches the means of component and structure modulation of transition metal phosphides.
Jing Yu,Yumeng Tian,Zaiwen Lin,Qi Liu,Jingyuan Liu,Rongrong Chen,Hongsen Zhang,Jun Wang
Combining a variety of factors to optimize the performances of electrocatalysts has become a new breakthrough for the development of low-cost electrolytic catalysts. In this work, we constructed N-doped carbon fibers as the substrate, which could provide high electronic conductivity and large surface area for the load of active catalysts, as well as close incorporation. The nanosheets morphology of NiSe 2 /Ni 5 P 4 is conducive to enlarging the specific surface area and exposing more active sites. The electrical conductivity is improved by the selenide and carbon nano-fiber substrate. The multiple features, including the unique structure characteristics, heterostructure of NiSe 2 and Ni 5 P 4 , and high electroconductivity , endow NiSe 2 /Ni 5 P 4 with superior catalytic activity towards water splitting. As a result, the overpotentials at the cathode current density of 10 and 100 mA cm −2 upon NiSe 2 /Ni 5 P 4 nanosheets are 112 and 350 mV in 0.5 M H 2 SO 4 . For oxygen evolution reaction (OER), the overpotential of NiSe 2 /Ni 5 P 4 nanosheets at a current density of 10 mA cm −2 in alkaline electrolyte is 316 mV. Furthermore, the bifunctional NiSe 2 /Ni 5 P 4 nanosheets exhibit excellent working stability for both HER, OER and overall water splitting, showing potential application in hydrogen energy.
危险品化学品经营许可证（带存储）