This paper presents a combinatorial deposition of a nano-thin film yttria-stabilized zirconia (YSZ) electrolyte deposited on a nanoporous anodic aluminum oxide (AAO) membrane, which serves as a supporting and gas-permeable substrate. The dense YSZ electrolyte was deposited by combining atomic layer deposition (ALD) and sputtering in an attempt to realize a pinhole-free electrolyte on a porous structure with a minimum electrolyte thickness. The YSZ electrolyte with an overall thickness of about 390 nm was successfully fabricated on porous AAO with this combined deposition method, and the open circuit voltage (OCV) of the cell with this electrolyte was verified to reach a high value of 1.14 V at 350 °C under an atmosphere of pure hydrogen and ambient air. The fuel cell performance reached power densities of 88, 129, and 180 mW cm⁻² at 350, 400, and 450 °C, respectively, and has been so far the highest attainable for a nanoscale thin film electrolyte on a porous substrate at such low temperatures. The addition of the pre-ALD YSZ layer also serves to confine the anode morphology and thus enhance the thermal stability of the metal electrodes.

We investigated the effect of electrolyte thickness and operating temperature on the heat and mass transfer characteristics of solid oxide fuel cells. We conducted extensive numerical simulations to analyze single cell performance of a planar solid oxide fuel cell (SOFC) with electrolyte thicknesses from 80 to 100 μm and operating temperatures between 700 °C and 800 °C. The commercial computational fluid dynamics (CFD) code was utilized to simulate the transport behavior and electrochemical reactions. As expected, the maximum power density increased with decreasing electrolyte thickness, and the difference became significant when the current density increased among different electrolyte thicknesses at a fixed temperature. Thinner electrolytes are beneficial for volumetric power density due to lower ohmic loss. Moreover, the SOFC performance enhanced with increasing operating temperature, which substantially changed the reaction rate along the channel direction. This study can be used to help design SOFC stacks to achieve enhanced heat and mass transfer during operation.

The hygroscopic property of particulate matter (PM) influencing light scattering and absorption is vital for determining visibility and accurate sensing of PM using a low-cost sensor. In this study, we examined the hygroscopic properties of coarse PM (CPM) and fine PM (FPM; PM_2.5) and the effects of their interactions with weather factors on visibility. A censored regression model was built to investigate the relationships between CPM and PM_2.5 concentrations and weather observations. Based on the observed and modeled visibility, we computed the optical hygroscopic growth factor, $$f\left( {RH} \right)$$f RH , and the hygroscopic mass growth, $$GM_{VIS}$$G M VIS , which were applied to PM_2.5 field measurement using a low-cost PM sensor in two different regions. The results revealed that the CPM and PM_2.5 concentrations negatively affect visibility according to the weather type, with substantial modulation of the interaction between the relative humidity (RH) and PM_2.5. The modeled $$f\left( {RH} \right)$$f RH agreed well with the observed $$f\left( {RH} \right)$$f RH in the RH range of the haze and mist. Finally, the RH-adjusted PM_2.5 concentrations based on the visibility-derived hygroscopic mass growth showed the accuracy of the low-cost PM sensor improved. These findings demonstrate that in addition to visibility prediction, relationships between PMs and meteorological variables influence light scattering PM sensing.

We demonstrate a new architecture for a low temperature solid oxide fuel cell to enlarge the lateral dimension of the fragile nano thin film electrolyte from the micrometer to millimeter scale with greatly enhanced mechanical stability.

An 8 nm-thick gadolinium-doped ceria (GDC) layer was inserted as a cathodic interlayer between the nanoscale proton-conducting yttrium-doped barium zirconate (BZY) electrolyte and the porous platinum cathode of a micro-solid oxide fuel cell (μ-SOFC), which has effectively improved the cathode reaction kinetics and rendered high cell power density. The addition of the GDC interlayer significantly reduced the cathodic activation loss and increased the peak power density of the μ-SOFC by 33% at 400 °C. The peak power density reached 445 mW/cm² at 425 °C, which is the highest among the reported μ-SOFCs using proton-conducting electrolytes. The impressive performance was attributed to the mixed protonic and oxygen ionic conducting properties of the nano-granular GDC, and also to the high densities of grain boundaries and lattice defects in GDC interlayer that favored the oxygen incorporation and transportation during the oxygen reduction reaction (ORR) and the water evolution reaction at cathode.

Sodium doping increases oxygen vacancy concentration, modulates the electronic structure, and improves CO₂ chemical adsorption, enabling superior CO₂/CO reversible conversion.