Enhanced bioelectrochemical performance by NiCoAl-LDH/MXene hybrid as cathode catalyst for microbial fuel cell

In this work, NiCoAl-layered double hydroxide (LDH)/MXene was successfully prepared through straightforward hydrothermal method. NiCoAl-LDH was tightly and uniformly coated on MXene, forming a kind of porous structure. NiCoAl-LDH/MXene exhibited the (002) (012) (105) (100) crystal planes of hydrotalcite reflection. NiCoAl-LDH/MXene also showed superior catalytic oxygen reduction reaction (ORR) in response current according to electrochemical test (cyclic voltammetry (CV) etc.). The maximum power density and output voltage of NiCoAl-LDH/MXene as cathode in microbial fuel cell (MFC) was 362.404 mW/m² and 450 mV, respectively, which was 1.54 times of MXene-MFC (234.256 mW/m²) and 1.71 times of NiCoAl-LDH-MFC (211.56 mW/m²). The results indicated that NiCoAl-LDH/MXene was a kind of potential cathode catalyst for MFC and was full of future application.     

Platinum nanoparticles decorated Nb2CTx MXene as an efficient dual functional catalyst for hydrogen evolution and oxygen reduction reaction

Here, a dual functional Nb₂CT_x@Pt nanocomposite has been synthesized by in situ reduction method. The Pt loading in the composite has been optimized to get minimum overpotential (141 mV at 10 mA/cm²) for hydrogen evolution reaction (HER) along with a promising Tafel slope of 46.3 mV/dec, while Pt/C shows an overpotential and Tafel slope of 104 mV and 32.4 mV/dec, respectively. The Pt mass activity for Nb₂CT_x@Pt3.8 composite at 100 mV overpotential was 3.44 A g^?1 while the Pt mass activity for conventional Pt/C was 0.7 A g^?1, which shows that the activity of Nb₂CT_x@Pt3.8 composite is approximately 5 times higher than Pt/C. In addition, the catalyst was found to be stable for continuous 500 cycles without any binder molecules. The oxygen reduction reaction (ORR) capability of the material was also evaluated and found that the catalyst exhibited a current density of ?4.28 mA/cm² in the diffusion limiting region in comparison with the current density of ?5.82 mA/cm² for Pt/C at 2600 revolutions per minute (RPM). The Pt mass activity of Nb₂CT_x@Pt3.8 composite for ORR is approximately 10 times higher than Pt/C. The Nb₂CT_x@Pt3.8 composite was able to reduce O₂ completely using the 4-electron pathway with very little peroxide production. From these results, the dual functionality of the Nb₂CT_x@Pt3.8 composite for both HER and ORR has been established.     

A durable and robust Fe–N–C electrocatalyst for oxygen reduction reactions by introducing Ti3C2–TiO2 as radical scavengers

Modern Fe–N–C electrocatalysts are promising as alternatives to expensive Pt-based catalysts for oxygen reduction reactions (ORR). Although the activity of this type of electrocatalyst have been improved over the years, their durability and longevity need critical enhancements for practical applications in fuel cells. Typically, the incomplete oxygen reduction inevitably generates reactive oxygen species, including ·OH and HO₂· radicals, which will fiercely attack the carbon support and directly damage active sites in Fe–N–C electrocatalysts. Herein, a durable and robust Fe–N–C@Ti₃C₂–TiO₂ electrocatalyst for high-efficiency ORR is synthesized, in which Ti₃C₂–TiO₂ could effectively scavenge ·OH radicals or decompose H₂O₂ molecules, and synergistically work with Fe–N–C catalysts to improve the durability. Consequently, the Fe–N–C@Ti₃C₂–TiO₂ electrocatalyst shows prominent ORR performance in both alkaline and acidic electrolytes, low H₂O₂ yield, and long-term stability. This work provides great prospects for the design of highly stable ORR electrocatalysts by introducing radical scavengers as an active defense to proactively eliminate H₂O₂ and its radicals.     

Cr2AlC陶瓷的无压合成及氢氟酸腐蚀行为研究

为了验证是否可以利用氢氟酸刻蚀Cr2AlC制备二维晶体MXene,本文采用气氛保护管式炉,在不同合成温度、保温时间及配比条件下制备出Cr2AlC样品,通过XRD图谱分析找出最佳原料配比为Cr∶ Al∶C =2∶ 1.1∶1,合成温度为1400℃,保温时间为1h.然后在此工艺条件下,制备疏松的样品,并用砂纸打磨去掉含有较多杂质的表层,然后把样品粉磨成大小不同的颗粒.这些颗粒放入氢氟酸中处理,将真空干燥后的反应产物进行XRD分析,结果表明Cr2AlC样品颗粒越小,反应时间越长,反应温度越高,HF酸浓度越高,Cr2AlC越容易被腐蚀,但是反应产物中均不存在二维晶体MXene,证明利用HF酸刻蚀Cr2 AlC制备二维晶体MXene的方法不可行.