Engineering topics

Seo, Sehun

Publications and source records attributed to Seo, Sehun.

3 records

DOE OSTI2023

Organometal Halide Perovskite‐Based Photoelectrochemical Module Systems for Scalable Unassisted Solar Water Splitting

Despite achievements in the remarkable photoelectrochemical (PEC) performance of photoelectrodes based on organometal halide perovskites (OHPs), the scaling up of small-scale OHP-based PEC systems to large-scale systems remains a great challenge for their practical application in solar water splitting. Significant resistive losses and intrinsic defects are major obstacles to the scaling up of OHP-based PEC systems, leading to the PEC performance degradation of large-scale OHP photoelectrodes. Herein, a scalable design of the OHP-based PEC systems by modularization of the optimized OHP photoelectrodes exhibiting a high solar-to-hydrogen conversion efficiency of 10.4% is suggested. As a proof-of-concept, the OHP-based PEC module achieves an optimal PEC performance by avoiding major obstacles in the scaling up of the OHP photoelectrodes. The constructed OHP module is composed of a total of 16 OHP photoelectrodes, and a photocurrent of 11.52 mA is achieved under natural sunlight without external bias. The successful operation of unassisted solar water splitting using the OHP module without external bias can provide insights into the design of scalable OHP-based PEC systems for future practical application and commercialization.

14 SOLAR ENERGY↗

DOE OSTI2023

TaO x electron transport layers for CO 2 reduction Si photocathodes

Electron transport layers (ETLs) used as components of photocathodes for light-driven CO 2 reduction (CO 2 R) in aqueous media should have good electronic transport, be stable under CO 2 R conditions, and, ideally, be catalytically inert for the competing hydrogen evolution reaction (HER). Here, using planar p-Si (100) as the absorbing material, we show that TaO x satisfies all three of the above criteria. TaO x films were synthesized by both pulsed laser deposition (PLD) and radio-frequency (RF) sputtering. In both cases, careful control of the oxygen partial pressure during growth was required to produce ETLs with acceptable electron conductivity. p-Si/TaO x photocathodes were interfaced with ca. 10 nm of a CO 2 R catalyst: Cu or Au. Under front illumination with simulated AM 1.5G in CO 2 -saturated bicarbonate buffer, we observed, for both metals, faradaic efficiencies for CO 2 R products of ~50% and ~30% for PLD TaO x and RF sputtered TaO x , respectively, at photocurrent densities up to 8 mA cm -2 . p-Si/TiO 2 /Cu photocathodes were also evaluated but produced mostly H 2 (>97%) due to reduction of the TiO 2 to Ti metal under CO 2 R conditions. In contrast, a dual ETL photocathode (p-Si/TiO 2 /TaO x /Cu) was selective for CO 2 R, which suggests a strategy for separately optimizing selective charge collection and the stability of the ETL/water interface. The maximum photovoltage obtained with p-Si/TaO x /Cu devices was 300 mV which was increased to 430–460 mV by employing ion implantation to make pn + -Si/TaO x /Cu structures. Photocathodes with RF sputtered TaO x ETLs are stable for CO 2 R for at least 300 min. In conclusion, techno-economic analysis shows that the reported system, if scaled, could allow for an economically viable production of feedstocks for chemical synthesis under the adoption of specific CO 2 credit schemes, thus becoming a significant component of carbon-neutral manufacturing.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Shape-Controlled NaTaO 3 by Flux-Mediated Synthesis

NaTaO 3 is a stable and wide bandgap n-type semiconductor material with many different applications. Here, a flux-mediated synthesis method is presented for NaTaO 3 resulting in highly distinctive, substrate covering shapes via precursor chemistry variation at comparatively low temperatures. It is found that the microstructure of the resulting NaTaO 3 films can be varied from nanocubes to smooth thin films. These shapes and surface chemistries can be correlated by employing density functional theory calculations and surface sensitive X-ray photoemission spectroscopy. This study provides guidance on how to synthesize the material and tailor its shape and surface termination for different applications. Finally, as a proof of concept of one possible application, NaTaO 3 is applied to perovskite solar cells as the electron transport layer, resulting in conversion efficiencies of >19%. Further, this study provides a new strategy for designing ternary oxide thin films for renewable energy applications.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗