Anomalous Size Effect of Pt Ultrathin Nanowires on Oxygen Reduction Reaction.

The classical size effect of Pt particles on oxygen reduction reaction (ORR) suggests that the activity and durability would decrease with reducing the particle size, self-limiting the effectiveness in maximizing the Pt utilization efficiency with the particle-size-reduction strategy. Herein, we discover an anomalous size effect based on Pt nanowires (NWs) with tunable diameters, where the monotonically increasing activity and durability for ORR were observed with decreasing the diameter from 2.4 to 1.1 nm. Our results reveal that the dominant role of increased compressive strain induced by decreasing the diameter of NWs in weakening the adsorption and suppressing the Pt dissolution accounts for this anomalous size effect, where the reduced low-coordinated sites on NWs, the intrinsic structural advantage, is the root. Our findings not only expand the knowledge to the classical size effect but also provide new implications to break through the size limit in the design of Pt-based ORR catalysts.

Stigma, Discrimination, and Hate Crimes in Chinese-Speaking World amid Covid-19 Pandemic.

The Covid-19 pandemic has given rise to stigma, discrimination, and even hate crimes against various populations in the Chinese language-speaking world. Using interview data with victims, online observation, and the data mining of media reports, this paper investigated the changing targets of stigma from the outbreak of Covid-19 to early April 2020 when China had largely contained the first wave of Covid-19 within its border. We found that at the early stage of the pandemic, stigma was inflicted by some non-Hubei Chinese population onto Wuhan and Hubei residents, by some Hong Kong and Taiwan residents onto mainland Chinese, and by some Westerners towards overseas Chinese. With the number of cases outside China surpassing that in China, stigmatization was imposed by some Chinese onto Africans in China. We further explore how various factors, such as the fear of infection, food and mask culture, political ideology, and racism, affected the stigmatization of different victim groups. This study not only improved our understanding of how stigmatization happened in the Chinese-speaking world amid Covid-19 but also contributes to the literature of how sociopolitical factors may affect the production of hate crimes.

Applications of Metal Nanocrystals with Twin Defects in Electrocatalysis.

Electrocatalytic energy conversion is one of the most promising pathways to develop clean and renewable energy technologies, and the development of high-performance electrocatalysts to improve the energy conversion efficiency is of paramount importance. Metal nanocrystals with twin defects possess unique features, including lattice strain and high density of low-coordinated atoms at the twin boundary, endowing them with excellent catalytic performance in various electrocatalytic reactions. Herein, we briefly summarize recent advances in the synthesis of metal nanocrystals with various twin structures, recent breakthroughs related to electrocatalytic applications of twin metal nanocrystals are also overviewed. Finally, the major challenges and perspectives for future development of twin metal nanocrystals in electrochemical applications are proposed.

Unconventional p-d Hybridization Interaction in PtGa Ultrathin Nanowires Boosts Oxygen Reduction Electrocatalysis.

Alloying 3d transition metals with Pt has been discovered as an effective strategy to boost the catalytic activity in oxygen reduction reaction (ORR), which, however, often raises the insufficient catalyst durability issue due to rapid leaching of the 3d metal elements. To overcome this issue and realize enhancements in both the activity and the durability properties, here we report a new catalytic structure based on PtGa ultrathin alloy nanowires (NWs), which feature an unconventional strong p-d hybridization interaction. Relative to commercial Pt catalyst, the optimum Pt4.31Ga NWs catalyst exhibited 10.5- and 12.1-fold enhancement in the ORR mass activity and specific activity, respectively. Particularly, the Pt4.31Ga NWs catalyst showed only 15.8% loss in the mass activity after 30 000 cycles of durability test, as compared to a big decrease of 79.6% for the commercial Pt catalyst. Our mechanistic studies find a strong p-d hybridization interaction between Ga and Pt that accounts for the improved ORR performance via synergistically optimizing the surface electronic structure, enhancing the oxidation resistance of Pt, and suppressing the leaching of lattice Ga. We believe this work provides new perspectives to design active and durable electrocatalysts toward ORR.

Accelerating oxygen evolution electrocatalysis of two-dimensional NiFe layered double hydroxide nanosheets via space-confined amorphization.

NiFe layered double hydroxides (LDHs) have received widespread attention due to their unique structures and inherent electrocatalytic activity towards the oxygen evolution reaction (OER). Extensive studies have been reported to further improve the electrocatalytic activity of NiFe-LDHs via various strategies. However, controlling the degree of amorphization and stabilizing the amorphous zone during the electrocatalytic process are still challenging. Here, we report a facile method to synthesize a space-confined amorphous NiFe-LDH (SCA-NiFe-LDH) by selectively etching the surfaces of electrocatalysts. Due to the successful anchoring of amorphous zones onto the basal planes of the two-dimensional NiFe-LDH, the optimized SCA-NiFe-LDH exhibits high electrocatalytic activity with a low overpotential of 190 mV at 10 mA cm-2, a Tafel slope of 31 mV dec-1 and excellent long-term stability. The substantially enhanced OER performance is attributed to the increased amount of active sites and the modified electronic structure of NiFe-LDH after amorphization.