The recent advances in electrocatalysis for oxygen reduction reaction (ORR) for proton exchange membrane fuel cells (PEMFCs) are thoroughly reviewed. This comprehensive Review focuses on the low- and non-platinum electrocatalysts including advanced platinum alloys, core–shell structures, palladium-based catalysts, metal oxides and chalcogenides, carbon-based non-noble metal catalysts, and metal-free catalysts. The recent development of ORR electrocatalysts with novel structures and compositions is highlighted. The understandings of the correlation between the activity and the shape, size, composition, and synthesis method are summarized. For the carbon-based materials, their performance and stability in fuel cells and comparisons with those of platinum are documented. The research directions as well as perspectives on the further development of more active and less expensive electrocatalysts are provided.

http://repository.ust.hk/ir/bitstream/1783.1-77094/1/acs.chemrev.5b00462_withlink.pdf

Recent Advances in Electrocatalysts for Oxygen Reduction Reaction

This article provides an up-to-date perspective on the use of anion-exchange membranes in fuel cells, electrolysers, redox flow batteries, reverse electrodialysis cells, and bioelectrochemical systems (e.g. microbial fuel cells). The aim is to highlight key concepts, misconceptions, the current state-of-the-art, technological and scientific limitations, and the future challenges (research priorities) related to the use of anion-exchange membranes in these energy technologies. All the references that the authors deemed relevant, and were available on the web by the manuscript submission date (30th April 2014), are included.

/pdf/anion-exchange-membranes-in-electrochemical-energy-systems-46uquenb56.pdf

Anion-exchange membranes in electrochemical energy systems

The development of low-cost, efficient, and stable electrocatalysts for the oxygen reduction reaction (ORR) is desirable but remains a great challenge. Herein, we made a highly reactive and stable isolated single-atom Fe/N-doped porous carbon (ISA Fe/CN) catalyst with Fe loading up to 2.16 wt %. The catalyst showed excellent ORR performance with a half-wave potential (E1/2) of 0.900 V, which outperformed commercial Pt/C and most non-precious-metal catalysts reported to date. Besides exceptionally high kinetic current density (Jk) of 37.83 mV cm−2 at 0.85 V, it also had a good methanol tolerance and outstanding stability. Experiments demonstrated that maintaining the Fe as isolated atoms and incorporating nitrogen was essential to deliver the high performance. First principle calculations further attributed the high reactivity to the high efficiency of the single Fe atoms in transporting electrons to the adsorbed OH species.

Isolated Single Iron Atoms Anchored on N-Doped Porous Carbon as an Efficient Electrocatalyst for the Oxygen Reduction Reaction

Spinels with the formula of AB2O4 (where A and B are metal ions) and the properties of magnetism, optics, electricity, and catalysis have taken significant roles in applications of data storage, biotechnology, electronics, laser, sensor, conversion reaction, and energy storage/conversion, which largely depend on their precise structures and compositions. In this review, various spinels with controlled preparations and their applications in oxygen reduction/evolution reaction (ORR/OER) and beyond are summarized. First, the composition and structure of spinels are introduced. Then, recent advances in the preparation of spinels with solid-, solution-, and vapor-phase methods are summarized, and new methods are particularly highlighted. The physicochemical characteristics of spinels such as their compositions, structures, morphologies, defects, and substrates have been rationally regulated through various approaches. This regulation can yield spinels with improved ORR/OER catalytic activities, which can furth...

Spinels: Controlled Preparation, Oxygen Reduction/Evolution Reaction Application, and Beyond

High-performance electrode materials are the key to advances in the areas of energy conversion and storage (e.g., fuel cells and batteries). In this Review, recent progress in the synthesis and electrochemical application of transition metal carbides (TMCs) and nitrides (TMNs) for energy storage and conversion is summarized. Their electrochemical properties in Li-ion and Na-ion batteries as well as in supercapacitors, and electrocatalytic reactions (oxygen evolution and reduction reactions, and hydrogen evolution reaction) are discussed in association with their crystal structure/morphology/composition. Advantages and benefits of nanostructuring (e.g., 2D MXenes) are highlighted. Prospects of future research trends in rational design of high-performance TMCs and TMNs electrodes are provided at the end.

/pdf/transition-metal-carbides-and-nitrides-in-energy-storage-and-33qhnc07u1.pdf

Transition Metal Carbides and Nitrides in Energy Storage and Conversion

This chapter introduces the application of biochar in soil water conservation and salinization control in agricultural land of arid desert regions. It begins by discussing the desertification and salinization in arid regions. In then explains the treatment methods and technology of soil water conservation and salinization control in agricultural land of arid desert regions. At the end of chapter the main advantages of biochar in soil water conservation and salinization control over other methods are explained.

Biochar for Soil Water Conservation and Salinization Control in Arid Desert Regions

Graphene-covered FePc as a model of the encapsulated type of catalyst for the oxygen reduction reaction

Simultaneous determination of 20 disperse dyes in foodstuffs by ultra high performance liquid chromatography-tandem mass spectrometry.

The flexible smart wearable device with low cost and high performance is highly desired but rather challenging. In this work, a wearable temperature sensor was developed by integrating the polybutylene terephthalate melt-blown nonwoven fabric (PBT NW) with reduced graphene oxide (rGO) and carbon nanotubes (CNTs) via a simple mechanical ultrasonication method. The microstructures of the rGO/[email protected] NW sensor were investigated by FT-IR, XRD, and SEM techniques, and the thermal and mechanical properties of this sensor were systematically analyzed. The conductive rGO and CNTs could be tightly fixed to the surface of PBT NW. Compared with original PBT NW, the tensile properties of rGO/[email protected] NW sensor were improved. The results of sensing performance tests showed that the prepared temperature sensor had high sensitivity (−0.737% °C−1) and linearity (R2 =0.98) with a resolution of 0.1 °C between 25 °C and 45 °C, a long-term stability and good circularity indicating that our sensor can meet the monitoring requirement of real-time human body temperature. In addition, this sensor could also be used to monitor human respiratory rate. Our study may provide a new idea for the fabrication of the flexible temperature sensor with nonwoven substratefor monitoring the human body and environment temperature. 

Flexible Temperature Sensor Based on RGO/CNTs@PBT Melting Blown Nonwoven Fabric

Federated learning (FL) enables multiple clients to collaboratively train a global model while keeping local data decentralized. Data heterogeneity (non-IID) across clients has imposed significant challenges to FL, which makes local models re-optimize towards their own local optima and forget the global knowledge, resulting in performance degradation and convergence slowdown. Many existing works have attempted to address the non-IID issue by adding an extra global-model-based regularizing item to the local training but without an adaption scheme, which is not efficient enough to achieve high performance with deep learning models. In this paper, we propose a Selective Self-Distillation method for Federated learning (FedSSD), which imposes adaptive constraints on the local updates by self-distilling the global model&#x2019;s knowledge and selectively weighting it by evaluating the credibility at both the class and sample level. The convergence guarantee of FedSSD is theoretically analyzed and extensive experiments are conducted on three public benchmark datasets, which demonstrates that FedSSD achieves better generalization and robustness in fewer communication rounds, compared with other state-of-the-art FL methods. 

Xiaodong Yang

Papers

Biochar for Soil Water Conservation and Salinization Control in Arid Desert Regions

Graphene-covered FePc as a model of the encapsulated type of catalyst for the oxygen reduction reaction

Simultaneous determination of 20 disperse dyes in foodstuffs by ultra high performance liquid chromatography-tandem mass spectrometry.

Flexible Temperature Sensor Based on RGO/CNTs@PBT Melting Blown Nonwoven Fabric

Learning Critically: Selective Self-Distillation in Federated Learning on Non-IID Data