Unraveling the pH-Dependent Oxygen Reduction Performance on Single-Atom Catalysts: From Single- to Dual-Sabatier Optima,Journal of the American Chemical Society

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Unraveling the pH-Dependent Oxygen Reduction Performance on Single-Atom Catalysts: From Single- to Dual-Sabatier Optima
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2024-01-12 , DOI: 10.1021/jacs.3c11246
Di Zhang _{1,

2} , Zhuyu Wang ₃ , Fangzhou Liu ₃ , Peiyun Yi ₂ , Linfa Peng ₂ , Yuan Chen ₃ , Li Wei ₃ , Hao Li ₁

Affiliation

Metal–nitrogen–carbon (M–N–C) single-atom catalysts (SACs) have emerged as a potential substitute for the costly platinum-group catalysts in oxygen reduction reaction (ORR). However, several critical aspects of M–N–C SACs in ORR remain poorly understood, including their pH-dependent activity, selectivity for 2- or 4-electron transfer pathways, and the identification of the rate-determining steps. Herein, by analyzing >100 M–N–C structures and >2000 sets of energetics, we unveil a pH-dependent evolution in ORR activity volcanos─from a single peak in alkaline media to a double peak in acids. We found that this pH-dependent behavior in M–N–C catalysts fundamentally stems from their moderate dipole moments and polarizability for O* and HOO* adsorbates, as well as unique scaling relations among ORR adsorbates. To validate our theoretical discovery, we synthesized a series of molecular M–N–C catalysts, each characterized by well-defined atomic coordination environments. Impressively, the experiments matched our theoretical predictions on kinetic current, Tafel slope, and turnover frequency in both acidic and alkaline environments. These new insights also refine the famous Sabatier principle by emphasizing the need to avoid an “acid trap” while designing M–N–C catalysts for ORR or any other pH-dependent electrochemical applications.

中文翻译：

揭示单原子催化剂上 pH 依赖性氧还原性能：从单 Sabatier 优化到双 Sabatier 优化

金属-氮-碳（M-N-C）单原子催化剂（SAC）已成为氧还原反应（ORR）中昂贵的铂族催化剂的潜在替代品。然而，ORR 中 M-N-C SAC 的几个关键方面仍然知之甚少，包括它们的 pH 依赖性活性、2 或 4 电子转移途径的选择性以及速率决定步骤的识别。在此，通过分析 > 100 个 M-N-C 结构和 > 2000 组能量学，我们揭示了 ORR 活动火山中 pH 依赖性的演化——从碱性介质中的单峰到酸性介质中的双峰。我们发现，M-N-C 催化剂中这种 pH 依赖性行为从根本上源于其适度的偶极矩和 O* 和 HOO* 吸附物的极化性，以及 ORR 吸附物之间独特的缩放关系。为了验证我们的理论发现，我们合成了一系列分子 M-N-C 催化剂，每种催化剂都具有明确的原子配位环境。令人印象深刻的是，这些实验与我们对酸性和碱性环境中的动力学电流、塔菲尔斜率和周转频率的理论预测相符。这些新见解还完善了著名的Sabatier原理，强调在为 ORR 或任何其他 pH 依赖型电化学应用设计 M-N-C 催化剂时需要避免“酸陷阱”。

更新日期：2024-01-12

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