Photoactive Earth-Abundant Iron Pyrite Catalysts for Electrocatalytic Nitrogen Reduction Reaction

Chia-Che Chang, Shin-Ren Li, Hung-Lung Chou,* Yi-Cheng Lee, Shivaraj Patil, Ying-Sheng Lin, Chun-Chih Chang, Yuan Jay Chang, and Di-Yan Wang*

Small, Just Accepted Manuscript
Publication Date (Web): October 14, 2019
The generation of ammonia, hydrogen production and nitrogen purification are considered as energy intensive processes accompanied with large amount of CO2 emission. The electrochemical method assisted by photo energy has been widely utilized for the chemical energy conversion. In this work, the earth-abundant iron pyrite (FeS2) nanocrystals grown on carbon fiber paper (FeS2/CFP) was found to be an electrochemical and photoactive catalysts for nitrogen reduction reaction (NRR) under ambient temperature and pressure. The electrochemical results revealed that FeS2/CFP achieved a high Faradaic efficiency (FE) ~14.14% and NH3 yield rate~ 0.096 mg/min at 0.6 V versus RHE electrode in 0.25 M LiClO4. During proceeding electrochemical catalytic reaction, the crystal structure of FeS2/CFP remained cubic pyrite phase analyzed by in-situ XRD measurement. Also, With near infrared laser irradiation (808 nm), NH3 yield rate of FeS2/CFP catalyst can be slightly improved to (0.1 mg/min) with high FE of 14.57%. Furthermore, density functional theoretical (DFT) calculations demonstrated that N2 molecule had strong chemical adsorption energy on the iron atom of FeS2. Overall, the iron pyrite-based materials have proven to be a potential electrocatalyst with photoactive behavior for ammonia production in practical applications.
Cover letter 53077

13 May. 2019. our work "Creation of three-dimensional textured graphene/Si Schottky junction photocathode for enhanced photoelectrochemical efficiency and stability" has been accepted by Advanced Energy Materials

Creation of three-dimensional textured graphene/Si Schottky junction photocathode for enhanced photoelectrochemical efficiency and stability

Che-Kuei Ku, Po-Hsien Wu, Cheng-Chu Chung, Chun-Chi Chen, Kai-Jie Tsai, Hung-Ming Chen, Yu-Cheng Chang, Cheng-Hao Chuang, Chuan-Yu Wei, Cheng-Yen Wen, Tzu-Yao Lin,1 Hsuen-Li Chen, Yen-Shang Wang, Zhe-Yu Lee, Jun-Ru Chang, Chih-Wei Luo, Di-Yan Wang,* Bing Joe Hwang,* Chun-Wei Chen*

This work demonstrates a novel three-dimensional pyramid-like graphene/p-Si Schottky junction photocathode for H2 production based on the unique advantages of excellent carrier transport, high transparency and superior corrosion protection of graphene. The formation of graphene/Si Schottky junctions with 3D architecture is a promising approach to improve the performance and durability of Si-based photoelectrochemical systems for water splitting or solar-to-fuel conversion.

123 4942d

Apr. 2019. our work "Plasmon-Enhanced Hydrogen Evolution on Specific Facet of Silver Nanocrystals" has been published on Chemistry of Materials in ASAP.

Plasmon-Enhanced Hydrogen Evolution on Specific Facet of Silver Nanocrystals

Tsung-Rong Kuo,*ab, Yi-Cheng Lee,c Hung-Lung Chou,*d Chuan-Yu Wei,e Cheng-Yen Wen,e Swathi MG,c Yi-Hsuan Chang,c Xi-Yu Pana and Di-Yan Wang*c

                                                                 TOC 2e2b8

Hydrogen evolution reaction (HER) from electrocatalytic water splitting is a promising technology to provide clean energy with low environmental impact for the future. In this work, plasmonic silver nanocubes (AgNCs) with (100) facet and silver nanooctahedrons (AgNOs) with (111) facet were applied as the light-harvesting catalysts for enhancing hydrogen production in the plasmon-activated HER electrochemical system. As light harvesters, AgNCs and AgNOs can efficiently absorb light ranging from ultraviolet to near-infrared to generate hot electrons for facilitating electrocatalytic HER. Both AgNCs and AgNOs revealed the light-harvesting capability to improve HER activities with laser irradiation. Moreover, the current densities of AgNOs with (111) facet were higher than those of AgNCs with (100) facet for electrocatalytic HER under irradiations with three different laser wavelengths. The density function theory (DFT) simulations revealed the adsorption energy of the surfaces followed the order Ag(111) < Ag(100), indicating that the hydrogen could be easily desorbed on the Ag(111) surface for HER. Both the experimental HER results and DFT simulations expressed that AgNOs with (111) facet were the excellent light harvesters in this study. Based on the DFT simulations of the H-Ag(111) and H-Ag(100) systems, the findings could be extended to other plasmon-enhanced HER electrochemical systems and would enable electrocatalysts to be tailored at the atomic level.

10 Jan 2019. our work "Insights into Dynamic Molecular Intercalation Mechanism for Al-C Battery by Operando Synchrotron X-ray Techniques" has been accepted by Carbon

Recently, a novel rechargeable Al ion battery (AIB) with high performance has been developed. Owing to its low cost, high-rate capability, excellent cyclability, and non-flammability, AIB provides a safe alternative to many commercial batteries used in the energy storage system. To improve its performance, identifying molecular structure and arrangement of chloroaluminate anion (AlCl4) intercalated in the graphite layer remains a great challenge. In this work, operando analysis of X-ray diffraction (XRD) measurement and X-ray absorption (XAS) spectroscopy were performed to investigate the intercalation of AlCl4 anion and related molecular arrangement in the graphite layers. The intercalated stage and intercalant gallery height of graphite cathode electrode during AIB battery operation were observed to be stage 3 and 9.22 Å, respectively. Furthermore, the spectral evolution from ex-situ XAS at the Al and Cl K-edge was associated with closely packed intercalation of AlCl4- molecules. With density functional theory (DFT) calculation, three simulated models of intercalated AlCl4 molecules in the graphite layer were revealed successfully, which explained possible molecular structures at different charging states. This analytical methodology paves the way for better understanding the structural transformation of molecular ions de-/ intercalation in graphite layers.

1 866a7

9 Jan 2019. our work "Enhanced Luminescence and Stability of Cesium Lead Halide Perovskite CsPbX3 Nanocrystals by Cu2- Assisted Anion Exchange Reactions has been accepted by The Journal of Physical Chemistry C

Inorganic CsPbX3 perovskite nanocrystals (NCs) have exhibited great optical properties, such as tunable emission wavelength, narrow emission line-widths, and high photoluminescent quantum yields. However, the unstable crystal structure of perovskite CsPbX3 NCs lead to a deterioration in optical performance. In this work, it is demonstrated that inorganic perovskite NCs, including CsPbCl3 and CsPbBr3-xClx NCs with excellent photoluminescence quantum yield and optical stability can be improved via anion exchange reaction treated with a new halide precursor consisting of copper halide (CuX2)-oleylamine (OLA) complexes. Unlike traditional perovskite synthesized processes for better crystalline structures operated at high temperatures, this work offers an economical method operable at the room temperatures. The treated CsPbX3 perovskite nanocrystals were characterized by in situ photoluminescence (PL) spectra and in-situ X-ray diffraction (XRD) and exhibited stable crystalline structures and enhanced photoluminescence. Cu2+ ions were only absorbed on the surface of perovskite NCs confirmed by the X-ray absorption spectroscopy (XAS) analysis. Density functional theory calculation explained that the origin of high stability and good crystallinity for treated perovskite NCs stemmed from adsorption of CuCl2 on perovskite’s surface to passivate defect sites during the recrystallization process.

TOC d8973