低结晶度AuPt-Ru/CNTs合金异质结作为高效多功能电催化剂

Low-Crystallinity and Heterostructured AuPt-Ru@CNTs as Highly Efficient Multifunctional Electrocatalyst

催化剂的活性与其结构紧密相关,研究催化剂的构效关系以及可控合成高效电催化剂,并探究其催化机制,一直是科学研究的核心。贵金属铂是优异的电解水析氢的催化剂,同时也是直接醇燃料电池阳极氧化的良好催化剂,而贵金属钌是优异的电解水析氧催化剂。这些与燃料电池及氢能相关的重要反应催化剂,可通过合成Pt、Au及Ru的合金催化剂,通过应力效应、电子效应及团簇效应,可有效提高金属催化剂的活性,并实现多功能电催化性能。本文报道了可控合成低结晶度的AuPt-Ru合金异质结,并通过元素扫描分析及X射线衍射分析确认其结构。该催化剂表现出了非常优异的电催化氧化乙醇活性,其归一化到Pt的质量活性达到了为21.4A·mg^(-1),远远高于对照组样品AuPt及RuAuPt混合相催化剂及文献报道样品。催化剂同样表现出了非常好的乙醇氧化稳定性,但是其活性的衰减与其Ru组分的流失紧密相关。我们同时通过电化学原位红外光谱,研究了该催化剂乙醇氧化中间产物,分析了其反应机理。该催化剂同样表现出了优异的碱性电解水析氢及析氧催化活性,其析氢电流10mA·cm^(-2)对应的过电位为30mV,Tafel斜率为45mV·dec^(-1),优于AuPt及RuPtAu对照组样品。该催化剂优异的电化学性能主要归结于其低结晶度和异质结及其伴随的应力效应及团簇效应。本报道提供了一种可控合成具有异质结结构的金属合金催化剂,突出了其对实现多功能、高性能合金电催化剂的重要性。

The catalytic activity of the catalysts is strongly dependent on the structure of the catalysts,and the exploration of their correlation and structure-controlled synthesis of the high-performance catalysts are always at the central.Currently,platinum(Pt)is the optimum catalyst for hydrogen evolution reaction(HER),oxygen reduction reaction(ORR)and alcohol oxidation reaction,while ruthenium(Ru)behaves as the champion catalyst for oxygen evolution reaction(OER)during water splitting.Preparing alloy catalysts with these precious metals can modulate the catalytic activity of these catalysts from the perspective of strain effect,ensemble effect and ligand effect.Here,we developed a strategy to deposit AuPt alloy as a solid solution phase on amorphous Ru supported on CNTs,thus forming AuPt-Ru heterostructures.The well-defined AuPt-Ru heterostructured catalysts were examined by X-ray diffraction and elemental mapping in high-angle annular dark-field scanning transition electron spectroscopy(HAADF-STEM).As compared to the high crystallinity AuPt alloy,AuPt alloy in AuPt-Ru heterostructure became amorphous,and AuPt-Ru showed superior catalytic activity toward ethanol oxidation reaction(EOR),achieving the mass activity of Pt as high as 21.44 A·mg^(-1)due to the high tolerance toward the poisoning species.The intermediates species of the EOR were also examined by in-situ FTIR spectroscopy.The stability of the catalysts toward EOR was also excellent and the degradation in the activity of the catalysts was strongly related to the loss of Ru content during the stability test.The heterostructured AuPt-Ru catalysts also exhibited the excellent alkaline HER and OER performances,superior to those of commercial Pt/C and RuO_(2)catalysts,ascribing to the amorphous state of AuPt-Ru heterostructure,and the modulation by strain and ensemble effects.This work highlights the importance in the design of the multicomponent heterostructures for the synthesis of high-performance and multifunctional electrocatalysts.