Materials Strategies Tackling Interfacial Issues in Catalyst Layers of Proton Exchange Membrane Fuel Cells.

The most critical challenge for the large-scale commercialization of proton exchange membrane fuel cells (PEMFCs), one of the primary hydrogen energy technologies, is to achieve decent output performance with low usage of platinum (Pt). Currently, the performance of PEMFCs is largely limited by two issues at the catalyst/ionomer interface, specifically, the poisoning of active sites of Pt by sulfonate groups and the extremely sluggish local oxygen transport toward Pt. In the past few years, emerging strategies are derived to tackle these interface problems through materials optimization and innovation. This perspective summarizes the latest advances in this regard, and in the meantime unveils the molecule-level mechanisms behind the materials modulation of interfacial structures. This paper starts with a brief introduction of processes and structures of catalyst/ionomer interfaces, which is followed by a detailed review of progresses in key materials toward interface optimization, including catalysts, ionomers, and additives, with particular emphasis on the role of materials structure in regulating the intermolecular interactions. Finally, the challenges for the application of the established materials and research directions to broaden the material library are highlighted.

Manipulating Pt-skin of porous network Pt-Cu alloy nanospheres toward efficient oxygen reduction.

Designing Pt-skin on the catalyst surface is critical to developing efficient and stable electrocatalysts toward oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. In this paper, an acidic reductant is proposed to synchronously manipulate in-situ growth of Pt-skin on the surface of alloyed Pt-Cu nanospheres (PtCuNSs) by a facile one-pot synthesis in an aqueous solution. Ascorbic acid can create a Pt-skin of three atomic layers to make the typical PtCu-alloy@Pt-skin core/shell nanostructure rather than the uniform alloys generated by using alkaline reductants. Surfactant as soft-template can make the alloyed PtCuNSs with a three-dimensional porous network structure. Multiple characterizations of XRD, XPS and XAFS are used to confirm Pt-alloying with Cu and formation of core/shell structure of such a catalyst. This PtCuNSs/C exhibits a half-wave potential of 0.913 V (vs. RHE), with mass activity and specific activity about 3.5 and 6.4 times higher than those of Pt/C, respectively. Fuel cell tests verify the excellent activity of PtCuNSs/C catalyst with a maximum power density of about 1.2 W cm-2. Moreover, this catalyst shows excellent stability, achieving a long-term operation of 40,000 cycles. Furthermore, theoretical calculations reveal the enhancement effect of characteristic PtCu-alloy@Pt-skin nanostructure on both catalytic ORR activity and stability.

Magnetic Nanobeads and De Novo Growth of Electroactive Polymers for Ultrasensitive microRNA Detection at the Cellular Level.

Detection of biomarkers at the cellular level can provide more accurate and comprehensive information that is important for early diagnosis of diseases and evaluation of new drugs. However, the interference of a large number of components in cells and the requirement of high sensitivity bring great challenges for their detection. Herein, a robust and enzyme-free electrochemical platform was proposed for microRNA-21 (miRNA-21) detection by integrating the efficient separation of magnetic nanobeads (MBs) with the multisignal amplification of strand displacement amplification (SDA) and electrochemically mediated atom transfer radical polymerization (eATRP). The eATRP is capable of de novo growth of a number of electroactive polymers on the electrode surface for signal amplification. Compared to simple hybridization, SDA and eATRP can enhance the signals by ∼35-fold, achieving high signal-to-noise ratio for low-abundant target detection. Owing to their superparamagnetism and strong magnetic response ability, MBs endow the method with excellent specificity and anti-interference ability to detect miRNA-21 in cells. Using MBs as capture carriers, SDA and eATRP for signal amplification, and gold nanoflower (AuNF)-modified electrodes as working electrodes, as low as 0.32 aM miRNA-21 was detected. Furthermore, the successful detection of miRNA-21 in cells indicated the great prospect of this method in the early diagnosis of cancers, life science research, and single-entity electrochemical detection.