36 research outputs found
Copper-based Photocatalysts with Well-defined Morphologies for Photocatalytic and Photoelectrochemical Applications
No full textWith growing interest in well-defined architectured photocatalysts, cuprous oxide (Cu2O) stands as a promising material due to its earth abundancy, ease in synthesis and band potential suitability for redox reactions. Severe photocorrosion is, however, the major hindrance of its practical use. Hence, studies to further understand Cu2O, intrinsically and extrinsically are needed to improve this material.
Arising from a lack of understanding in Cu2O photocorrosion, systematic investigations in this regard were performed. It was revealed that Cu2O self-oxidation is the dominant photocorrosion pathway, where hole was readily consumed for self-oxidation without external hole scavenger in liquid-based photocatalytic reactions. This work reveals that efficient extraction of hole from Cu2O is vital to improve its photostability. Being a hole scavenger that has high redox potential, Na2SO3 has good scavenging ability that shows more profound improvement than other organic scavengers. With constant H2-evolving rate, Cu2O stabilization is established in Na2SO3 solution.
Following Cu2O stabilization, Chapter 4 demonstrates better performance of rhombic dodecahedral (RD-Cu2O) when compared to cubic Cu2O (CB-Cu2O), due to their distinct carrier dynamic. With the introduction of time resolved microwave conductivity measurement, higher carrier mobility computed for RD-Cu2O was attributed to its lower defect density. This work evaluates all facet-dependent properties including defect density, diverting from conventional justifications, comprised of surface band structure and adsorption ability.
Next, performance of dual faceted-truncated octahedral Cu2O (DF-Cu2O) was compared with single-faceted rhombic dodecahedral Cu2O (SF-Cu2O). Given their similar defect densities, DF-Cu2O is expected to have better activity due to its better charge separation efficiency. However, enhanced photoactivity of SF-Cu2O was observed instead, credited to the higher carrier mobility that has more profound effect to the activity when compared to charge separation efficiency under current experimental conditions.
The last section focuses on transformation of Cu2O into non-oxide photocatalyst via simple yet scalable route: ion-exchange method. Hollow CuxS structure was fabricated under controlled synthesis while irregular-shaped was obtained via direct mixing of precursors. Beneficial role of hollow cubic structure in suppressing agglomeration and maintaining sufficient active sites was demonstrated
Unraveling the structure-activity-selectivity relationships in furfuryl alcohol photoreforming to H2 and hydrofuroin over ZnxIn2S3+x photocatalysts
No full textZnxIn2S3+x has emerged as a promising candidate for alcohol photoreforming based on C-H activation and C-C coupling. However, the underlying structure-activity-selectivity relationships remain unclear. Here we report on ZnxIn2S3+x with varying Zn:In:S ratios for visible-light-driven furfuryl alcohol reforming into H2 and hydrofuroin, a jet fuel precursor, via C-H activation and C-C coupling. S-• radicals are directly identified as the catalytically active sites responsible for C-H activation in furfuryl alcohol, promoting selectivity toward H2 and hydrofuroin. The optimum ZnxIn2S3+x activity derives from a trade-off between enhanced carrier dynamics and diminished visible light absorption as the x value in ZnxIn2S3+x increases. Further, a higher Zn-S:In-S layer ratio prolongs the S-• lifetime in the Zn-S layer, promoting C-H activation and delivering a higher C-C coupling product selectivity. The findings represent a step toward further establishing sulfide-based photocatalysts for sustainable H2 production via organic photoreforming.Denny Gunawan, Jodie A. Yuwono, Priyank V. Kumar, Akasha Kaleem, Michael P. Nielsen, Murad J.Y. Tayebjee, Louis Oppong-Antwi, Haotian Wen, Inga Kuschnerus, Shery L.Y. Chang, Yu Wang, Rosalie K. Hocking, Ting-Shan Chan, Cui Ying Toe, Jason Scott, Rose Ama
Solar driven ammonia synthesis with Co-TiOx and Ag nanowires enhanced Cu2ZnSnS4 photocathodes
No full textRestoring ammonia from waste nitrate stands as a promising strategy for reducing reliance on the energyintensive Haber-Bosch process and tackling environmental pollutants. Advancing the catalytic aspects of photoelectrochemical (PEC) ammonia synthesis via waste nitrate reduction is of great importance to enhance its viability for sustainable chemical production. However, this process still suffers from low ammonia faradaic efficiency (FE) with high operational potential due to its involvement in multi-electron reactions. Herein, we integrated a cobalt-doped TiOx (Co-TiOx) cocatalyst and Ag nanowires (NWs) electron extraction layer onto TiOx/CdS/Cu2ZnSnS4 (CZTS) photocathode, achieving nearly 100 % ammonia FE and an onset potential of ~0.49 V vs. RHE. Evidenced by the in-situ synchrotron-radiated FTIR (SR-FTIR) and theoretical calculations, the increased ratio of surface oxygen vacancy sites (Vo) induced by Co-TiOx is crucial for the key reaction intermediates adsorption (i.e. *NO3 and *NO2) for subsequent ammonia production. Moreover, the transparent Ag NWs facilitates the electron extraction from TiOx/CdS/CZTS to the surface catalytic sites. Powered by CZTS solar cells, a standalone solar-to-ammonia system has been demonstrated with outstanding activity and catalytic performance.Shujie Zhou, Kaiwen Sun, Cui Ying Toe, Jialiang Huang, Ao Wang, Jodie Yuwono, Priyank Kumar, Tao Wan, Doudou Zhang, Zhipeng Ma, Jitraporn Vongsvivut, Dewei Chu, Xiaojing Hao, Rose Ama
Atomically Dispersed Cu Catalysts on Sulfide-Derived Defective Ag Nanowires for Electrochemical CO2 Reduction
No full textPublished: February 2, 2023Single-atom catalysts (SACs) have shown potential for achieving an efficient electrochemical CO2 reduction reaction (CO2RR) despite challenges in their synthesis. Here, Ag2S/Ag nanowires provide initial anchoring sites for Cu SACs (Cu/Ag2S/Ag), then Cu/Ag(S) was synthesized by an electrochemical treatment resulting in complete sulfur removal, i.e., Cu SACs on a defective Ag surface. The CO2RR Faradaic efficiency (FECO2RR) of Cu/Ag(S) reaches 93.0% at a CO2RR partial current density (jCO2RR) of 2.9 mA/cm2 under −1.0 V vs RHE, which outperforms sulfur-removed Ag2S/Ag without Cu SACs (Ag(S), 78.5% FECO2RR with 1.8 mA/cm2jCO2RR). At −1.4 V vs RHE, both FECO2RR and jCO2RR over Cu/Ag(S) reached 78.6% and 6.1 mA/cm2, which tripled those over Ag(S), respectively. As revealed by in situ and ex situ characterizations together with theoretical calculations, the interacted Cu SACs and their neighboring defective Ag surface increase microstrain and downshift the d-band center of Cu/Ag(S), thus lowering the energy barrier by ∼0.5 eV for *CO formation, which accounts for the improved CO2RR activity and selectivity toward related products such as CO and C2+ products.Zhipeng Ma, Tao Wan, Ding Zhang, Jodie A. Yuwono, Constantine Tsounis, Junjie Jiang, Yu-Hsiang Chou, Xunyu Lu, Priyank V. Kumar, Yun Hau Ng, Dewei Chu, Cui Ying Toe, Zhaojun Han, and Rose Ama
Recent advances in suppressing the photocorrosion of cuprous oxide for photocatalytic and photoelectrochemical energy conversion
No full textIdentifying Key Design Criteria for Large-Scale Photocatalytic Hydrogen Generation from Engineering and Economic Perspectives
No full textPhotocatalytic
hydrogen (H2) generation has emerged
as a promising approach for direct conversion of solar energy into
green H2 fuel. Prior works predominantly focused on photocatalyst
material development and optimization with photoreactor and system
design receiving considerably less attention. Further, significantly
less focus has been devoted to the economic feasibility study of photoreactor
systems. Therefore, this Perspective contemplates photoreactor design
and scale up from an economic viewpoint. The economics of two popular
large-scale photoreactor designs, (i) panel and (ii) slurry based,
are evaluated. This Perspective suggests that the design of a photocatalytic
slurry system is approximately 12% more cost effective than a panel
photoreactor system under the base-case scenario in producing 10 kg
H2/day. The analysis also suggests that a cost reduction
of up to 75% can be achieved if the photon conversion efficiency is
increased from 1% to 5%, indicating that research and development
should continue to be undertaken to increase process efficiency via
photocatalyst and system engineering. In addition, other considerations,
such as improving photocatalyst reusability (to give a photocatalyst
lifespan of at least 1 year), reducing photocatalyst cost (using non-noble-metal-based
photocatalysts) and increasing input photon density (installing a
solar concentrator to harness more than 1 Sun intensity), will each
impose an additional 20–30% of the cost
Synergistic Cyanamide Functionalization and Charge-Induced Activation of Nickel/Carbon Nitride for Enhanced Selective Photoreforming of Ethanol
No full textPhotoreforming
is a promising alternative to water splitting for
H2 generation due to the favorable organic oxidation half-reaction
and the potential to simultaneously produce solar fuel and value-added
chemicals. Recently, carbon nitride has received significant attention
as an inexpensive photocatalyst for the photoreforming process. However,
the application of carbon nitride continues to be hampered by its
poor photocatalytic performance. Herein, we report for the first time
a synergistic modification of an in situ photodeposited
Ni cocatalyst on carbon nitride via cyanamide functionalization
and solid/liquid interfacial charge-induced activation using excess
Ni2+ ions. Synergism between the cyanamide functionalization
and charge-induced activation by the excess Ni2+ ions invokes
enhanced activity, selectivity, and stability during ethanol photoreforming.
A H2 evolution rate of 2.32 mmol h–1 g–1 in conjunction with an acetaldehyde production rate
of 2.54 mmol h–1 g–1 was attained
for the Ni/NCN-CN. The H2 evolution rate and elevated acetaldehyde
selectivity (above 98%) remained consistent under prolonged light
illumination. To understand the origin of the complementary promotional
effects, the contributions of cyanamide groups and excess Ni2+ ions to selective ethanol photoreforming are decoupled and systematically
investigated. The cyanamide functionality on carbon nitride was found
to promote hole scavenging for the ethanol oxidation reaction, thereby
enabling effective electron transfer to the Ni cocatalyst for H2 evolution. Concomitantly, excess Ni2+ ions remaining
in solution created a positively charged environment on the photocatalyst
surface, which improved charge carrier utilization and ethanol adsorption.
The work highlights the importance of both carbon nitride functionality
and charge on the photocatalyst surface in developing a selective
photocatalytic reforming system
[[alternative]]According to Fourier series to establish a model to assess different degree of rowing technique
No full text[[abstract]]ABSTRACT
The purpose of the study was to establish the data of motion in different degree college rower. According to the data to establish the regression model that will be applied to assess different degree of rowing technique. In the experiment, bjects (includes collage’s students, players of ROC, players who obtain medals of world’s games) are forty-eight rowers who are age 22.39±1.72 years old, weight 60.44±10.29 Kilos, height 178.81±7.48 cm. The study analyze the motion of rowers in the ConceptⅡ by motion analysis systems and ConceptⅡ rowing systems. We set the of the video camera Shutter speed is 1/500, the frames speed is 30Hz, and the distance from camera to rowers is 15 meters, the stroke of the ConceptⅡ is set 30-31 times for one minute, and the air resistance is set on the level of 5, the rowing distance is 500 meters. The eleven body landmarks (includes head, shoulder, elbow, wrist, oar, hip, knee, ankle, heel, toe and chair) were digitized with the software of the Peak Motus 7.0,and the and body center of mass were estimated by using the Jin-cherng Wang data (1999), and the data of Fourier number were got through the Fourier series analysis. SPSS is tryout the efficient parameters and establish forecast model, and then we could authenticate the degree of the rowers.
The results of study show that we could use the efficient parameters [includes the Hand of first number (H1), Hand of second number (H2), wrist of second number (W2), knee of second number (K2), gravity of second number (M2), relative angle 0f hip joint third number (RH3)] and stepwise regression model (D=2.210 - 1.071H1 - 2.279 H2 - 5.630 W2 + 15.335 K2 + 7.907 M2 + 0.08025RH3) to predicate the degree of rowing technique for the collage’s students in Taiwan.
Key words：Biomechanics, Rowing, Fourier series, Degree, Technique.
Scalable solar-driven reforming of alcohol feedstock to H(2) using Ni/Zn(3)In(2)S(6) photocatalyst
No full textCorrected by: Corrigendum to “Scalable solar-driven reforming of alcohol feedstock to H2 using Ni/Zn3In2S6 photocatalyst” [Chem. Eng. J. 513 (2025) 162965], Chemical Engineering Journal, Volume 515, 1 July 2025, 163701. The authors regret that the published version of the above article contained typographical errors in the areal activity units reported in Sections 3.3 and 4. Specifically, “mol h–1 m–2” should have been written as “mmol h–1 m–2”. These errors have now been corrected in both the PDF and HTML versions of the article. We confirm that this correction does not affect the published results. The authors would like to apologize for any inconvenience caused.Organic photoreforming represents a promising pathway for solar H₂ generation with the coproduction of valuable byproducts. However, its development has been limited by separate studies on photocatalysts or photoreactors, with little focus on cost and scalability. Here we integrate photocatalyst design, upscaled photoreactor engineering, and cost analysis for the solar-driven reforming of alcohol feedstock to H₂. The process was optimized by examining various alcohol compounds and Ni cocatalyst impact on Zn₃In₂S₆ photocatalytic activity. Strong interactions between Zn₃In₂S₆ and both aromatic benzyl alcohol substrate and Ni intensified H₂ evolution and benzaldehyde formation, achieving an apparent quantum yield of 63.8 % at 420 nm and an areal H₂ evolution activity of 278 mmol h⁻¹ m⁻² under simulated sunlight. Using the optimum conditions established in a laboratory environment, an upscaled slurry photoreactor prototype was designed and operated under natural sunlight with a 0.5 m² light receiving area. The upscaled solar-driven reforming of benzyl alcohol over Ni/ Zn₃In₂S₆ delivered a H₂ production rate of 1.67 normal L h⁻¹, corresponding to an areal H₂ evolution activity of 139 mmol h⁻¹ m⁻², with benzaldehyde as the major organic byproduct. A pathway for commercially viable large-scale solar-driven organic reforming was defined through techno-economic assessment. The findings are a crucial advancement in scaling photoreforming towards commercialization.Denny Gunawan, Tahlia Stern, Jiajun Zhang, Jodie A. Yuwono, Jian Pan, Qiyuan Li, Haolin Yu, Michael Gunawan, Rosalie K. Hocking, Cui Ying Toe, Jason Scott, Rose Ama
Tuning the Selectivity of LaNiO3 Perovskites for CO2 Hydrogenation through Potassium Substitution
No full textHerein, we demonstrate a method used to tune the selectivity of LaNiO3 (LNO) perovskite catalysts through the substitution of La with K cations. LNO perovskites were synthesised using a simple sol-gel method, which exhibited 100% selectivity towards the methanation of CO2 at all temperatures investigated. La cations were partially replaced by K cations to varying degrees via control of precursor metal concentration during synthesis. It was demonstrated that the reaction selectivity between CO2 methanation and the reverse water gas shift (rWGS) could be tuned depending on the initial amount of K substituted. Tuning the selectivity (i.e., ratio of CH4 and CO products) between these reactions has been shown to be beneficial for downstream hydrocarbon reforming, while valorizing waste CO2. Spectroscopic and temperature-controlled desorption characterizations show that K incorporation on the catalyst surface decrease the stability of C-based intermediates, promoting the desorption of CO formed via the rWGS prior to methanation
