The development of new electrode materials with high specific capacity for excellent supercapacitive storage and energy conversion is highly desirable. The combination of metal and metal oxide with carbon is an effective strategy to achieve active bimetallic nanocatalysts. Herein, we developed a facile method to synthesize CoxMn1-xO@GC and Co/MnO@GC nanocomposites by an in situ conversion of Co-Mn PBAs. The as-prepared carbon hybrids, especially the resulting Co/MnO@GC carbonized under 700 °C (Co/MnO@GC-700), preserve the nanocubic morphology of Co-Mn PBAs and show excellent supercapacitance and OER performance. Specifically, an outstanding specific capacitance of 2275 F g-1 can be obtained with Co/MnO@GC-700 as the electrode material at a current density of 4 A g-1. When used as OER catalysts, Co/MnO@GC-700 shows a low overpotential of only 358 mV at 10 mA cm-2 in 1 M KOH. Moreover, a fabricated asymmetric supercapacitor device (ASC device), in combination with active carbon, shows a high cell voltage of 1.7 V and a considerably high specific capacitance of 246 F g-1 at 2 A g-1. Our nanoarchitecture design derived from PBAs provides a new opportunity for future applications in high-performance energy storage and transformation systems.
As one of the most promising photocatalysts, graphitic carbon nitride (g-CN) shows a visible light response and great chemical stability. However, its relatively low photocatalytic efficiency is a major obstacle to actual applications. Here an effective and feasible method to dramatically increase the visible light photocatalytic efficiency by forming CN/BiFeO ferroelectric heterojunctions is reported, wherein the band alignment and piezo-/ferroelectricity have synergistic positive effects in accelerating the separation of the photogenerated carriers. At the optimum composition of 10 wt% BiFeO, the heterojunction shows 1.4 times improved photocatalytic efficiency than that of the pure CN. Most importantly, mechanical pressing and electrical poling can also improve the photocatalytic efficiencies by 1.3 times and 1.8 times, respectively. The optimized photocatalytic efficiency is even comparable with that of some noble metal based compounds. These results not only prove the improved photocatalytic activity of the CN-ferroelectric heterojunctions, but also provide a new approach for designing high-performance photocatalysts by taking advantage of ferroelectricity.
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