多维度纳米三元过渡金属氧化物用于双功能电解水制氢催化剂

Multi-Dimensional Ternary Nano-Transition Metal Oxides as Bifunctional Electrocatalysts for Water Electrolysis to Hydrogen Production

摘要:

由于低廉的成本、简易的制备方法和优异的电化学性能，过渡金属氧化物被认为是一种有前景的碱性电解水制氢催化剂，但其形貌的电化学性能研究目前尚少。本文设计了一种多维度（一维、二维）齿轮形貌的纳米过渡金属氧化物碱性电解水制氢催化剂（NF/NCFO-g）。在1M KOH溶液、100 mA cm^-2电流密度的条件下，NF/NCFO-g展现出了0.23 V的阳极过电位和0.29 V的阴极过电位，以及196 mV dec^-1（阳极）和233 mV dec^-1（阴极）的Tafel斜率，优于一维纳米针状结构（NF/NCFO-n）和二维纳米片状结构（NF/NCFO-s）催化剂。NF/NCFO-g具备优异的电催化性能得益于一维纳米针的“顶端优势”和二维片状结构的表面电荷效应的协同作用。“顶端优势”使得电荷大量聚集在尖端处，从而压缩了内层电容宽度，而二维表面电荷有助于形成更多的氧空位活性位点，进而优化过渡态的反应能量。此外，在高电流密度下，一维纳米针结构能够增强亲水性而减小气泡半径，从而加速了气泡的释放。

Abstract:

Transition metal oxides are considered as potential catalysts for hydrogen production in alkaline water electrolysis due to their low cost， easy fabrication， and excellent electrochemical properties. But the investigation of their morphology on catalyst performance is insufficient. In this paper， multi-dimensional （one-dimensional （1D）， two-dimensional （2D）） gear-shaped transition metal oxide catalysts （NF/NCFO-g） are designed and used as bifunctional electrocatalysts for hydrogen production. In the 1 M KOH solution and a 100 mA cm-2 current density， NF/NCFO-g exhibited anodic overpotential of 0.23 V and a cathodic overpotential of 0.29 V， as well as Tafel slopes of 196 （anodic） and 233 mV dec-1 （cathode）， which are superior to both 1D （NF/NCFO-n） and 2D （NF/NCFO-s） catalysts. The synergistic effect between the “apical advantage” of the 1D nanoneedle and the surface charge effect of the 2D sheet structure are responsible for the excellent electrocatalytic performance of NF/NCFO-g. The “apical advantage” causes a large amount of charge to accumulate at the tip， rendering the inner layer capacitance width being reduced， while the surface charge of 2D sheet structure helps form more oxygen vacancy active sites， resulting in an optimized reaction energy of the transition state. In addition， at high current densities， the 1D nanoneedle structure enhances hydrophilicity and reduces the bubble radius， thus accelerating the bubbles release.