Facet-Dependent Catalytic Performance of Au Nanocrystals for Electrochemical Nitrogen Reduction
Facet-Dependent Catalytic Performance of Au Nanocrystals for Electrochemical Nitrogen Reduction
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Au 纳米晶体电化学氮还原的面依赖性催化性能
DOI：
10.1021/acsami.0c13414
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
Peng Chen
中科院分区：
文献类型：
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作者：
Weiqing Zhang;Yongli Shen;Fangjie Pang;Darren Quek;Wenxin Niu;Wenjun Wang;Peng Chen
纳米结构金属催化剂由于其优异的电催化性能，包括电化学氮还原（ENRR），引起了人们极大的兴趣。然而，他们的ENRR的工作机制仍然没有完全理解。本文合成了七种单晶面多面体Au纳米晶，并对其进行了系统的比较，以阐明Au晶面与NRR性能之间的关系。结果发现，具有高折射率小面的多面体催化性能优于具有低折射率小面的多面体。具体而言，（321）面包围的Au纳米星显示出2.6 μg h-1cm-2（20 μg h-1 mg-2）的高NH3产生速率和10.2%的法拉第效率（在-0.2 V下），分别是（100）面包围的纳米立方体的3.1倍和5.1倍。理论研究表明，H ~+还原为H ~* 的能垒（ΔGH ~*）越大，越能抑制HER在Au（321）表面的发生，从而保证了较好的NRR选择性。同时，N2 H2 * 在催化剂表面生成的能垒越低，N2 H2 * 分解为N2和2 H * 的能垒越大，NH3的产率越高。本研究提供了ENRR的机理见解和合理设计的金属纳米晶体的电催化。
Nanostructured metal catalysts have attracted great interest due to their extraordinary performance for electrocatalysis including electrochemical nitrogen reduction (ENRR). However, their working mechanisms for ENRR are still not fully understood. Herein, seven monofaceted polyhedral Au nanocrystals were synthesized and systemically compared to elucidate the relation between Au crystal facets and NRR performance. It is found that polyhedra with high-index facets catalytically outperform those with low-index facets. Specifically, Au nanostars enclosed with (321) facets show a high NH3production rate of 2.6 μg h–1cm–2(20 μg h–1mg–2) and faradaic efficiency of 10.2% at −0.2 V, which are 3.1- and 5.1-folds larger than those of nanocubes enclosed with (100) facets. As revealed by theoretical investigation, a larger energy barrier for reduction of H+to H* (ΔGH*) hinders occurrence of HER on the Au(321) surface, thus ensuring better NRR selectivity. Meanwhile, a lower energy barrier for formation of N2H2* on the catalyst surface and a larger energy barrier for decomposing the formed N2H2* back into N2and 2H* jointly favor a higher NH3production rate. This study provides mechanistic insights into ENRR and rational design of metal nanocrystals for electrocatalysis.