Choi Yun-Hyuk
School of Advanced Materials and Chemical Engineering, Daegu Catholic University, Gyeongsan 38430, Korea.
Nanomaterials (Basel). 2022 Mar 12;12(6):939. doi: 10.3390/nano12060939.
Herein, we report high electrocatalytic activity of monoclinic VO (M1 phase) for the oxygen evolution reaction (OER) for the first time. The single-phase VO (M1) nanoparticles are prepared in the form of uniformly covering the surface of individual carbon fibers constituting a carbon fiber paper (CFP). The VO nanoparticles reveal the metal-insulator phase transition at 65 °C (heating) and 62 °C (cooling) with low thermal hysteresis, indicating a high concentration of structural defect which is considered a grain boundary among VO nanoparticles with some particle coalescence. Consequently, the VO/CFP shows a high electrocatalytic OER activity with the lowest η (350 mV) and Tafel slope (46 mV/dec) values in a 1 M aqueous solution of KOH as compared to those of the vacuum annealed VO and the hydrothermally grown VO (M1), α-VO, and γ'-VO. The catalytically active site is considered V components and V redox couples in VO. The oxidation state of V is revealed to be more favorable to the OER catalysis compared to that of V in vanadium oxide through comparative studies. Furthermore, the amount of V component is found to be increased on the surface of VO catalyst during the OER, giving rise to the performance degradation. This work suggests V and its redox couple as a novel active component for the OER in metal-oxide electrocatalysts.
在此，我们首次报道了单斜晶系VO（M1相）对析氧反应（OER）具有高电催化活性。单相VO（M1）纳米颗粒以均匀覆盖构成碳纤维纸（CFP）的单根碳纤维表面的形式制备。VO纳米颗粒在65℃（加热）和62℃（冷却）时显示出金属-绝缘体相变，且热滞小，这表明存在高浓度的结构缺陷，该缺陷被认为是VO纳米颗粒之间存在一些颗粒聚结的晶界。因此，与真空退火的VO以及水热生长的VO（M1）、α-VO和γ'-VO相比，VO/CFP在1 M KOH水溶液中表现出高电催化OER活性，具有最低的η（350 mV）和塔菲尔斜率（46 mV/dec）值。催化活性位点被认为是VO中的V组分和V氧化还原对。通过对比研究发现，与氧化钒中的V相比，V的氧化态对OER催化更有利。此外，在OER过程中，VO催化剂表面的V组分含量增加，导致性能下降。这项工作表明V及其氧化还原对是金属氧化物电催化剂中OER的新型活性组分。
