Hu Wenbin and Zhong Cheng team of Tianjin University: using the strategy of "electrochemical deposition based on organic-inorganic double template" to prepare mesoporous self-supporting palladium nanotube array catalyst

Formic acid fuel cell and formate fuel cell as a new type of green energy system have been widely concerned, but they are seriously constrained by the lack of high-performance and low-cost formic acid / formate oxidation (FAO / for) catalysts in the process of commercialization PD based catalysts have lower raw material price, higher low voltage activity and higher tolerance to carbon monoxide poisoning than Pt based catalysts However, it is still a big challenge to obtain the best performance of FAO / for bifunctional catalysis with the least amount of palladium Recently, Hu Wenbin and Zhong Cheng team of Tianjin University proposed a strategy of "electrochemical deposition based on organic-inorganic double template" to prepare mesoporous self-supporting palladium nanotube array catalyst (p-pdnta) The organic-inorganic composite double sacrificial template was obtained by in-situ loading the liquid crystal film formed by self-assembly of phytanol on the inner wall of AAO The template can accurately guide the nucleation point, deposition rate and growth direction of PD in the electrochemical deposition process, and obtain stable PD nanotube arrays with an average thickness of only 12 nm The liquid crystal template can create a large number of mesopores and high surface energy anisotropic secondary structures on the wall of PD nanotube The presence of mesopores makes the electrochemical active area of p-pdnta catalyst 3.4 times that of commercial Pd / C catalyst At the same time, p-pdnta catalyst showed excellent dual function catalytic performance of FAO and for, respectively, 8.5 times and 6.5 times of commercial Pd / C due to its unique medium transport characteristics and high active site density brought by secondary structure Furthermore, the influence of the surface chemistry of the liquid-solid interface on the formation of noble metal nanotubes in the electrodeposition cell was studied, and the formation mechanism of noble metal nanotubes / wires was proposed This achievement was published in advanced energy materials (DOI: 10.1002/aenm.201900955) under the title of "mesoporous decision of freestanding palladium nanotube arrays boosts the electrocatalys capabilities toward formal acid and format oxidation", and recommended as the current cover story The mesopores were further modified on the ultra-thin PD nanotubes, which greatly improved the electrochemical activity area The one-dimensional nanotube array structure perpendicular to the collector ensures the fast transport of reactants and products in the system and avoids the loss of active area caused by agglomeration of common powder catalysts Figure 1 Schematic diagram of p-pdnta catalyst preparation process by electrochemical deposition of organic-inorganic double template (source: advanced energy materials) Figure 2 Morphology and mesoporous structure of p-pdnta catalyst (source: advanced energy materials) light field image and high angle ring dark field image display of transmission electron microscope, liquid crystal sacrificial mode The existence of the plate greatly improves the transmittance of the nanotubes to the incident electron beam to obtain the translucent contrast and the black spots uniformly distributed in the dark field image, which proves the existence of a large number of mesopores on the nanotube wall Figure 3 Product morphology, deposition site, growth direction and rate (source: advanced energy materials) under different electrolyte concentrations The influence of different electrolyte concentrations and the presence of liquid crystal template on the formation of PD nanotubes / lines reveals the influence of surface chemical properties of solid-liquid interface in electroplating cell on The determination of the formation of PD nanotubes Figure 4 FAO / for dual function catalytic performance of p-pdnta catalyst (source: advanced energy materials) p-pdnta catalyst shows excellent electrocatalytic performance for the oxidation of formic acid and formate radical in acid and alkaline medium This special bifunctional catalytic property is at the forefront of PD based catalysts To sum up, this work achieved a further breakthrough on the basis of the preparation of conventional one-dimensional nanostructured noble metal catalysts The unique organic-inorganic double templates were used to obtain stable self-supporting mesoporous PD nanotube arrays, and showed great potential for electrocatalysis At the same time, the mechanism that the surface chemistry of solid-liquid interface affects the morphology of the products in the process of electrodeposition was studied systematically, and a new idea to precisely control the electrodeposition process of precious metals was proposed The first authors of this paper are Dr Ding Jia, School of materials, Tianjin University and Dr Liu Zhi, School of materials, Shanghai Jiaotong University.