The ability to exfoliate transition metal diborides has led to a renewed interest in their prospect to be applied as catalysts for electrochemical reactions. This is due to an enhanced access to the unprecedented interfaces these nanomaterials offer. In this work, we show that nanosheets exfoliated from TiB₂ exhibit vacancies that facilitate an excellent interface for catalyzing nitrogen reduction reaction (NRR). We found that these nanosheets demonstrate a high selectivity toward NH₃ because of their abiity to preferentially chemisorb and activate N₂. These nanosheets exhibit a superlative NH₃ yield of 318 μg h^–1 cm^–2 at −0.2 V versus RHE with a faradaic efficiency of 57%. We also found how the relative ratios of Ti and B atoms in these nanosheets can affect the NH₃ yield and faradaic efficiency. We supplement these results with DFT studies that indicate that it is the creation of frustrated Lewis pairs along with the Ti–B synergy that induces a push-and-pull effect; this in turn favors N₂ activation and lowers the energy barrier for NRR. Furthermore, we explored B-exposed and Ti-exposed surfaces to understand how different surfaces affect the reaction yield and efficiency and found that Ti-exposed surfaces with boron divacancy have the highest propensity for NRR. The maiden insights presented in this study on the role of transition metal–boron synergy and interfaces present significant additions to the fast-expanding knowledge on nanoscaled metal borides.

中文翻译：

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富含空位的 TiB2 纳米片促进电化学氨合成

剥离过渡金属二硼化物的能力引起了人们对其作为电化学反应催化剂的前景的新兴趣。这是因为这些纳米材料提供了前所未有的界面。在这项工作中，我们表明从 TiB ₂剥离的纳米片表现出空位，有利于催化氮还原反应（NRR）的良好界面。我们发现这些纳米片表现出对NH _{3 的}高选择性，因为它们能够优先化学吸附和激活N ₂。这些纳米片在-0.2 V 下与 RHE 相比表现出318 μg h ^–1 cm ^{–2的最高 NH} ₃产率，法拉第效率为 57%。我们还发现这些纳米片中 Ti 和 B 原子的相对比例如何影响 NH ₃产率和法拉第效率。我们用 DFT 研究补充了这些结果，表明是受挫路易斯对的产生以及 Ti-B 协同作用引起了推拉效应；这反过来有利于 N ₂活化并降低 NRR 的能垒。此外，我们探索了 B 暴露和 Ti 暴露表面，以了解不同表面如何影响反应产率和效率，并发现具有硼双空位的 Ti 暴露表面具有最高的 NRR 倾向。这项研究中提出的关于过渡金属-硼协同作用和界面作用的首次见解为快速扩展的纳米级金属硼化物知识提供了重要补充。