Graphical Cobalt phthalocyanine was supported on N-doped MXene via axial coordination and π-π stacking. The formed axial coordination configuration N−Co−N 4 can effectively break the planar structure of Co-N 4 and enhance the oxygen reduction performance with an E 1/2 of 0.863 V, which is better than the 20 wt.% Pt/C catalyst of 0.85 V. The precise control of electronic configurations of catalytic sites via molecular engineering is significantly desirable for boosting electrocatalytic activity. We reported a new-type composite electrocatalyst with cobalt phthalocyanine supported on N-doped MXene nanosheets (N-MXene/CoPc) through a self-assembly process. Beneficial from the joint action of N sites participation and axial coordination, N-MXene/CoPc exhibits a high ORR activity with positive onset potential (E onset =0.98 V vs. RHE) and half-wave potential (E 1/2 =0.863 V), which is superior over the pristine CoPc (E 1/2 =0.72 V) and the composite with undoped MXene as support (MXene/CoPc, E 1/2 =0.771 V). Additionally, N-MXene/CoPc exhibits an excellent durability with only 8.5 % attenuation after 25000 s of continuous i-t test, while a more obvious decay 18.6 % for 20 wt.% Pt/C. This work not merely reported a robust ORR catalyst, but more provides a reasonable design strategy for nonnoble-metal catalysts through catalyst-support interactions.
Song-Yi Liao,Shuai-Fu Cui,Yue-Zhu Li,Wei-Xiang Cheng,Xing-Wen Huang,Jing Zhang,Ting-Ting Cui,Xu-Gang Shu,Yong-Gang Min
In this work, the wrinkled, flexible, and layered nitrogen-doped Ti 3 C 2 T x (shorten as N-MXene) is synthesized by using cyanamide as N-dopants. The changeable (002) plane spacing and the attached functional groups of N-MXene are detected by XRD and XPS analyses in details, respectively. The microscopic morphology of N-MXene is characterized by SEM and TEM, which demonstrates its wrinkled and flexible characteristics. When the wrinkled N-MXene being added into the LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) as conductive additive, the attained electrodes obtain enhanced electrochemical performances at the appropriate weight ratio (namely 2.5-N-MXene with 2.5 wt.%). The 2.5-N-MXene delivers “extra” capacity of 226.9 mAh/g at 0.1 C (20 mA/g) current density. The “extra” capacity is assigned to Li ions intercalation/extraction from the wrinkled/flexible/layered N-MXene. Moreover, based on the analyses of CV and dQ/dV curves, the wrinkled/flexible N-MXene additive could effectively inhibit the phase transition of M↔H2 of NCM811 and alleviate the volume change of the particles in the circulation. From DFT simulation, the N-MXene is more capable of preventing Ni/Co/Mn from dissolving and migrating to the negative electrode to form dendrites through adsorption. Therefore, the N-MXene should be a very competitive conductive agent to improve the mechanical and electrochemical properties of high nickel cathode materials.
Shuyue Yang,Dongmei Zhang,Jie Xu,Zongping Zhang,Shibing Ni
High theoretical capacity and safety performance endow Li 3 VO 4 with great promising as anode material for Li-ion batteries. However, approaches and inner mechanisms to advance the performance of Li 3 VO 4 are limited. Herein, we demonstrate for the first time, continuously-high pseudocapacitive charge storage triggered by N doped MXene in a Li 3 VO 4 -based electrode, resulting in excellent comprehensive electrochemical performance. The hybrid electrode delivers high discharge capacity of 515.2 mAh g −1 after 500 cycles at 0.1 A g −1 . After periodic rate performance test from 0.1 to 2.0 A g −1 for 410 cycles, the capacity of the hybrid electrode can be fully recovered. Followed by additional 1000 cycles at 0.5 A g −1 , the hybrid electrode still delivers high discharge capacity of 457.6 mAh g −1 . The robust capacitive charge storage induced by N doped MXene and the remarkable comprehensive electrochemical performance are referential for the design of high performance Li 3 VO 4 -based anode material, and the facile approach is beneficial for mass production toward practical application. Graphical abstract Download : Download high-res image (210KB) Download : Download full-size image N doped MXene induced robust pseudocapacitive charge storage in a Li 3 VO 4 electrode is firstly demonstrated responsible for the excellent comprehensive electrochemical performance.
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