In situtransformation of Pd into β-PdH is the origin of the high selectivity for CO in the electrochemical CO2reduction reaction using Pd as the electrocatalyst.

Electrochemical CO2 reduction reaction (CO2RR) with renewable electricity is a potentially sustainable method to reduce CO2 emissions. Palladium supported on cost‐effective transition‐metal carbides (TMCs) are studied to reduce the Pd usage and tune the activity and selectivity of the CO2RR to produce synthesis gas, using a combined approach of studying thin films and practical powder catalysts, in situ characterization, and density functional theory (DFT) calculations. Notably, Pd/TaC exhibits higher CO2RR activity, stability and CO Faradaic efficiency than those of commercial Pd/C while significantly reducing the Pd loading. In situ measurements confirm the transformation of Pd into hydride (PdH) under the CO2RR environment. DFT calculations reveal that the TMC substrates modify the binding energies of key intermediates on supported PdH. This work suggests the prospect of using TMCs as low‐cost and stable substrates to support and modify Pd for enhanced CO2RR activity.

The emergence of the SARS‐CoV‐2 pandemic and airborne particulate matter (PM) pollution has led to remarkably high demand for face masks. However, conventional respirators are intended for single use and made from nondegradable materials, causing serious concern for a plastic‐waste environmental crisis. Furthermore, these facemasks are weakened in humid conditions and difficult to decontaminate. Herein, a reusable, self‐sustaining, highly effective, and humidity‐resistant air filtration membrane with excellent particle‐removal efficiency is reported, based on highly controllable and stable piezoelectric electrospun poly (l‐lactic acid) (PLLA) nanofibers. The PLLA filter possesses a high filtration efficiency (>99% for PM 2.5 and >91% for PM 1.0) while providing a favorable pressure drop (≈91 Pa at normal breathing rate) for human breathing due to the piezoelectric charge naturally activated by respiration through the mask. The filter has a long, stable filtration performance and good humidity resistance, demonstrated by a minimal declination in the filtration performance of the nanofiber membrane after moisture exposure. The PLLA filter is reusable via common sterilization tools (i.e., an ultrasonic cleaning bath, autoclave, or microwave). Moreover, a prototype of a completely biodegradable PLLA nanofiber‐based facemask is fabricated and shown to decompose within 5 weeks in an accelerated degradation environment.

There is high demand in the medical field for rapid fabrication of biodegradable patches at low cost and high throughput for various instant applications, such as wound healing. Bioprinting is a promising technology, which makes it possible to fabricate custom biodegradable patches. However, several challenges with the physical and chemical fidelity of bioprinted patches must be solved to increase the performance of patches. Here, we presented two hybrid hydrogels made of alginate-cellulose nanocrystal (CNC) (2% w/v alginate and 4% w/v CNC) and alginate-TEMPO oxidized cellulose nanofibril (T-CNF) (4% w/v alginate and 1% w/v T-CNC) via ionic crosslinking using calcium chloride (2% w/v). These hydrogels were rheologically characterized, and printing parameters were tuned for improved shape fidelity for use with an extrusion printing head. Young’s modulus of 3D printed patches was found to be 0.2–0.45 MPa, which was between the physiological ranges of human skin. Mechanical fidelity of patches was assessed through cycling loading experiments that emulate human tissue motion. 3D bioprinted patches were exposed to a solution mimicking the body fluid to characterize the biodegradability of patches at body temperature. The biodegradation of alginate-CNC and alginate-CNF was around 90% and 50% at the end of the 30-day in vitro degradation trial, which might be sufficient time for wound healing. Finally, the biocompatibility of the hydrogels was tested by cell viability analysis using NIH/3T3 mouse fibroblast cells. This study may pave the way toward improving the performance of patches and developing new patch material with high physical and chemical fidelity for instant application.