北京大学郭少军团队报道了原子层IrOx实现的配体效应促进水氧化电催化。相关研究成果于2024年7月8日发表于国际顶尖学术期刊《美国化学会志》。

由阳极偏压驱动的原位形成的IrO_x（x≤2）层是用于析氧反应（OER）电催化的Ir基材料的重要活性位点。一旦被限制在原子厚度内，这种IrOx层就具有有利的配体效应和最大化的具有较低O配位数的活性Ir位点。然而，由于对表面重建动力学的理解不足，获得IrOx的原子层在实验上仍然具有挑战性。

该文中，研究人员报道了一种使用金属间IrVMn纳米颗粒，原位诱导超薄IrO_x层（O-IrVMn/IrO_x）形成的材料设计思想，以实现配体效应，从而实现优异的OER电催化。理论计算预测，源自有序原子排列的强电子相互作用，可以有效地阻碍过渡金属的过度浸出，使氧配位的空位最小化。线性X射线吸收近边缘光谱分析、扩展X射线吸收精细结构拟合结果和X射线光电子能谱共同证实，由于不饱和O配位的存在，Ir在O-IrVMn/IrO_x中以较低的氧化态存在。

因此，O-IrVMn/IrO_x具有优异的酸性OER性能，在10 mA cm^–2下的过电位仅为279 mV，在1.53 V（相对于RHE）下的高质量活性为2.3 A mg^–1，超过了大多数报道的Ir基催化剂。此外，O-IrVMn/IrO_x也显示出优异的催化稳定性，在电化学氧化下只有0.05at.%Ir溶解，远低于无序的D-IrVMn/IrO_x（0.20at.%）。密度泛函理论计算表明，增强的配体效应优化了OER中涉及的多种中间体的吸附能，并稳定了所形成的催化IrOx层。

附：英文原文

Title: Atomic-Layer IrOx Enabling Ligand Effect Boosts Water Oxidation Electrocatalysis

Author: Heng Luo, Fangxu Lin, Qinghua Zhang, Dawei Wang, Kai Wang, Lin Gu, Mingchuan Luo, Fan Lv, Shaojun Guo

Issue&Volume: July 8, 2024

Abstract: An in situ formed IrOx (x ≤ 2) layer driven by anodic bias serves as the essential active site of Ir-based materials for oxygen evolution reaction (OER) electrocatalysis. Once being confined to atomic thickness, such an IrOx layer possesses both a favorable ligand effect and maximized active Ir sites with a lower O-coordination number. However, limited by a poor understanding of surface reconstruction dynamics, obtaining atomic layers of IrOx remains experimentally challenging. Herein, we report an idea of material design using intermetallic IrVMn nanoparticles to induce in situ formation of an ultrathin IrOx layer (O-IrVMn/IrOx) to enable the ligand effect for achieving superior OER electrocatalysis. Theoretical calculations predict that a strong electronic interaction originating from an orderly atomic arrangement can effectively hamper the excessive leaching of transition metals, minimizing vacancies for oxygen coordination. Linear X-ray absorption near edge spectra analysis, extended X-ray absorption fine structure fitting outcomes, and X-ray photoelectron spectroscopy collectively confirm that Ir is present in lower oxidation states in O-IrVMn/IrOx due to the presence of unsaturated O-coordination. Consequently, the O-IrVMn/IrOx delivers excellent acidic OER performances with an overpotential of only 279 mV at 10 mA cm–2 and a high mass activity of 2.3 A mg–1 at 1.53 V (vs RHE), exceeding most Ir-based catalysts reported. Moreover, O-IrVMn/IrOx also showed excellent catalytic stability with only 0.05 at. % Ir dissolution under electrochemical oxidation, much lower than that of disordered D-IrVMn/IrOx (0.20 at. %). Density functional theory calculations unravel that the intensified ligand effect optimizes the adsorption energies of multiple intermediates involved in the OER and stabilizes the as-formed catalytic IrOx layer.

DOI: 10.1021/jacs.4c05165

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.4c05165