High-Throughput Synthesis and Screening of Pt-Based Ternary Electrocatalysts Using a Microfluidic-Based Platform

Pt-based electrocatalysts have received extensive attention owing to their wide applications in various fields, including fuel cells, hydrogen production, degradation of organic pollutants, electrochemical sensors, and oxidation of small molecules. Therefore, the efficient synthesis and screening of high-performance Pt-based electrocatalysts is necessary for accelerating their further development and application in these fields. The conventional method for developing the advanced materials and optimizing their synthesis parameters is time-consuming, inefficient, and costly. Microfluidic high-throughput techniques have the great potential for optimizing the synthesis parameters of Pt-based electrocatalysts. However, microfluidic high-throughput synthesis without performance evaluation cannot maximize its advantages. Therefore, it is highly desirable to develop a platform that combines the high -throughput synthesis of materials and the evaluation of their properties in a high-throughput fashion to improve the overall screening efficiency of the novel materials. In this study, a versatile microfluidic high-throughput platform, combining the high-throughput synthesis and screening of materials, was constructed. The microfluidic chip generated 20-level concentration gradients of the three different precursors. Microreactor arrays with 100 microchannels were used for the material synthesis and electrochemical characterization. A wide range of concentration combinations of the three different precursor solutions was achieved using the microfluidic chip. Five groups of Pt-based ternary electrocatalysts (100 different components in total) were synthesized and electrochemically characterized using the designed platform. The obtained Pt -based electrocatalysts exhibited a loose particle morphology, and were composed of small nanoparticles. The efficient preparation of Pt-based electrocatalysts with controllable compositions was also achieved through the high-throughput synthesis platform. The catalytic performance of the Pt-based catalysts towards oxygen evolution reaction (OER) was characterized by chronoamperometry. The optimal composition of Pt-based ternary electrocatalysts for OER was directly determined using the designed platform. For NiPtCu, the samples with a relatively high atomic percentage (approximately 50%) of Pt (i.e., Ni0.30Pt0.56Cu0.14, Ni0.17Pt0.52Cu0.31 and Ni0.12Pt0.48Cu0.40) exhibited higher electrocatalytic activity and stability, whereas the samples with a relatively high atomic percentage (> 50%) of Cu possessed lower activity and stability. For AuPtNi and AuPtCu, the samples wherein Au and Pt accounted for a large proportion of the sample (i.e., Ni or Cu < 10%) and the atomic ratios of Au : Pt were (3-4) : 1, e.g., Au0.71Pt0.25Ni0.04 and Au0.77Pt0.18Cu0.05, displayed high electrocatalytic activity and stability. As the atomic fraction of Au decreased, the atomic ratio of Pt and Ni in AuPtNi approached 3 : 1 or that of Pt and Cu in AuPtCu reached to 1 : 1, the samples (Au0.54Pt0.35Ni0.11, Au0.35Pt0.42Cu0.23, Au0.27Pt0.41Cu0.32 and Au0.12Pt0.32Cu0.56) all demonstrated high electrocatalytic activity and stability. The samples (Pt0.06Cu0.94) wherein the atomic percentages of Au and Pt were all less than 10%, exhibited poor electrocatalytic activity and stability. For RhPtNi and RhPtCu, when the atomic percentage of Rh in RhPtNi and RhPtCu was high (50%-90%) and almost no Ni or Cu was present, the samples (Rh0.91Pt0.09 and Rh0.82Pt0.18 for RhPtNi, as well as Rh0.88Pt0.12 and Rh0.75Pt0.21Cu0. 04 for RhPtCu) all had high electrocatalytic activity and stability. As the atomic percentage of Rh decreased and that of Pt increased, the atomic percentages of Rh and Pt were relatively close, Rh0.54Pt0.32Ni0.14 and Rh0.51Pt0.36Cu0.14 showing high electrocatalytic activity and stability. When the atomic percentages of Ni and Cu were high (> 50%), the RhPtNi and RhPtCu samples all showed the relatively poor electrocatalytic activity and stability. These results demonstrate the high efficiency and flexibility of the constructed microfluidic high-throughput platform, which significantly shortens the cycle for the development cycle of new materials and the optimization of their properties.

Automated summary

Pt-based electrocatalysts have been extensively studied for their wide applications in fuel cells, hydrogen production, degradation of organic pollutants, electrochemical sensors, and oxidation of small molecules. The conventional method for developing advanced materials is time-consuming and inefficient, while microfluidic high-throughput techniques offer great potential for optimizing synthesis parameters. However, performance evaluation is necessary to maximize the advantages of microfluidic high-throughput synthesis. Therefore, a versatile microfluidic high-throughput platform combining synthesis and screening of materials was constructed, which showed high efficiency and flexibility in developing new materials and optimizing their properties.