Zhao Li

Bio: Zhao Li is an academic researcher from Villanova University. The author has contributed to research in topics: Materials science & Photocatalysis. The author has an hindex of 1, co-authored 1 publications receiving 2 citations.

Photogenerated hole traps in metal-organic-framework photocatalysts for visible-light-driven hydrogen evolution

Abstract: Efficient electron-hole separation and carrier utilization are key factors in photocatalytic systems. Here, we use a metal-organic framework (NH2-UiO-66) modified with inner platinum nanoparticles and outer cadmium sulfide (CdS) nanoparticles to construct the ternary composite Pt@NH2-UiO-66/CdS, which has a spatially separated, hierarchical structure for enhanced visible-light-driven hydrogen evolution. Relative to pure NH2-UiO-66, Pt@NH2-UiO-66, and NH2-UiO-66/CdS samples, the Pt@NH2-UiO-66/CdS composite exhibits much higher hydrogen yields with an apparent quantum efficiency of 40.3% at 400 nm irradiation and stability over the most MOF-based photocatalysts. Transient absorption measurements reveal spatial charge-separation dynamics in the composites. The catalyst's high activity and durability are attributed to charge separation following an efficient photogenerated hole-transfer band-trap pathway. This work holds promise for enhanced MOF-based photocatalysis using efficient hole-transfer routes.

Tuning the Cobalt–Platinum Alloy Regulating Single‐Atom Platinum for Highly Efficient Hydrogen Evolution Reaction

Abstract: Designing atomically dispersed metal catalysts for the electrocatalytic hydrogen evolution reaction (HER) is a promising strategy to efficiently convert electrical energy to chemical fuels. This strategy, however, still faces the challenge of finding a catalyst with high activity and long‐term durability. Here, single‐atom platinum and cobalt–platinum‐alloy nanocrystals in a nitrogen‐doped porous‐carbon framework (CoPt‐PtSA/NDPCF) is confined. The electrocatalyst exhibits ultralow overpotentials under both alkaline and acidic conditions at a high current density of −300 mA cm−2 and excellent long‐term durability up to 100 h or 10 000 cycles, which are attributed to the synergetic effects of PtSA and tuning of the CoPt alloy in the NDPCF. First‐principles calculations suggested that PtSA aided by the CoPt alloy has high d‐band occupation for promoting the reaction kinetics. This study opens a new avenue for designing heterostructures with the synergic effects of single metal atoms and metal alloys with outstanding performance in the HER.

Defect-Mediated Electron Transfer in Pt-CuInS2/CdS Heterostructured Nanocrystals for Enhanced Photocatalytic H2 Evolution

Abstract: The effective separation of photogenerated electrons and holes is the key to improve photocatalytic activity in hydrogen evolution reaction (HER). However, the mechanism of photoinduced charge transfer between the cocatalyst and the semiconducting heterojunction in a single nanocrystal is vague at present. Herein, the relationships between the crafted cocatalyst and the constructed semiconducting heterojunction in a single nanocrystal were verified. Manipulating these relationships will improve the performance of visible light-driven hydrogen evolution. As a model, we used CuInS2 (CIS) nanocrystals (NCs) modified by the cocatalyst platinum (Pt) NCs and the semiconductor cadmium sulfide (CdS), forming the ternary heterostructured NCs (HNCs). Under visible light irradiation, the photocatalytic activity in hydrogen evolution of Pt-CIS/CdS HNCs is 6.38 and 1.76 times higher than those of pristine CIS NCs and CIS/CdS HNCs, respectively. Transient absorption measurements certified that the high photocatalytic activity in the HER was attributed to the photoinduced electron transfer from the defect-mediated trap state in CIS to the cocatalyst Pt, which was superior to the direct Z-scheme heterojunction between CIS and CdS. This research paves a route for the design of a suitable cocatalyst and the formation of heterostructured semiconducting NCs for boosting the photocatalytic activity in solar energy conversion.

Interfacial architecting with anion treatment for enhanced thermoelectric power of flexible ternary polymer nanocomposites

Abstract: Organic polymer thermoelectrics (TEs) that can realize direct heat-to-electricity conversion hold great potential in flexible and wearable applications and thus are receiving tremendous attention. Constructing polymer-based nanocomposites represents an effective approach in achieving high TE performance, while current studies on the underlying mechanisms for the improvement of TE properties in aspects of interfacial nanostructures are insufficient. In this work, flexible ternary nanocomposite films with unique interfacial architectures are developed by sequential electrochemical polymerization of conducting polymers and subsequent anion treatment. The optimized interfacial architectures contribute to enhanced π electron conjugation, which facilitates interfacial charge transfer and favours large-area charge transport. The anion treatment further enables the molecular chains to arrange in a more ordered configuration, leading to improved carrier mobility. As a result, the nanocomposites exhibit high power factors of more than 500 μW m−1 K−2 that outperform most of the literature-reported peer composites. The feasible interfacial architecting and anion treatment methods proposed in this study demonstrate high potential in designing high-performance TE nanocomposites.

Localized Surface Plasmon Resonance Promotes Metal–Organic Framework‐Based Photocatalytic Hydrogen Evolution

Abstract: Combining metal nanoparticles (NPs) featured with localized surface plasmon resonance (LSPR) with metal–organic framework (MOF)-based photocatalysts is a novel means for achieving efficient separation of electron–hole pairs. Herein, the [email protected]2-UiO-66/CdS composites are successfully synthesized by encapsulating Au NPs with LSPR into the NH2-UiO-66 nanocage, further growing CdS NPs on the surface of the NH2-UiO-66, which exhibits higher photocatalytic activity in hydrogen evolution reaction under visible-light irradiation than that of NH2-UiO-66/CdS and CdS, respectively. Transient absorption measurements reveal that MOF is not only a transit station for electrons generated from CdS to Au, but also a receiver for hot electrons generated from plasmonic Au in [email protected]/CdS composites. Thus, the LSPR-induced hot electron transfer from Au NPs is an important manifestation to prolong the carrier lifetime and enhance the photocatalytic performance. This work provides insights into investigating the photoinduced carrier dynamics of nanomaterials with LSPR effects for enhancing the MOF-based photocatalytic performance.

Superb All‐pH Hydrogen Evolution Performances Powered by Ultralow Pt‐Decorated Hierarchical Ni‐Mo Porous Microcolumns

Abstract: Achieving efficient and robust hydrogen evolution reaction (HER) electrocatalysts under all‐pH conditions is significant for clean hydrogen production. Herein, an ultralow Pt‐decorated hierarchical Ni‐Mo porous hybrid, consisting of Ni3Mo3N on MoO2 microcolumns, is developed for all‐pH HER with remarkable catalytic performances, owing to the porous structure, strong metal‐support interaction, along with ultralow Pt nanoparticles and multichannel nickel foam support. The superhydrophilic and aerophilic surfaces favor mass transport during the HER process. Consequently, the porous Pt/Ni‐Mo‐N‐O microcolumns present remarkable HER activity and durability with low overpotentials of 40.6, 101.1, and 89.5 mV to obtain 100 mA cm−2 in basic, neutral, and acid media, respectively. Moreover, the excellent performance in alkaline seawater (40.4 mV@100 mA cm−2) even suppresses most of over‐reported catalysts. More importantly, the two‐electrode cell, assembled with Pt/Ni‐Mo‐N‐O and NiMoO4 as cathode and anode, exhibits excellent performance towards overall‐water electrolysis with an ultralow cell voltage of 1.56 V@100 mA cm−2.

Metal Sulfide Photocatalysts for Hydrogen Generation: A Review of Recent Advances

Abstract: Metal-sulfide nanostructures have piqued the interest of researchers for decades due to their intriguing optoelectronic properties. Indeed, significant advances and improvements have been made in various fundamental aspects for cutting-edge applications, such as water splitting and hydrogen production. Furthermore, rising demand for low-dimensional materials due to lower material consumption and improved performance due to quantum size effects has spurred research on semiconducting metal sulfides. Consequently, size-controllable nanostructures with diverse morphologies have been fabricated and studied for potential applications. However, the photocatalytic hydrogen evolution rate is still limited mainly by fast recombination rate, poor solar energy utilization and lack of surface-active sites for H2 reduction. This review will highlight particularly recent findings in metal-sulfide-based photocatalysts for hydrogen evolution reactions, considering the swift development and excellent research in this field. Following a brief overview of fundamental properties, we will explore state-of-the-art strategies for enhancing H2 generation efficiencies over the pristine, heterostructured and co-catalayzed metal-sulfide photocatalysts.

Flexible and Foldable Films of SWCNT Thermoelectric Composites and an S-Shape Thermoelectric Generator with a Vertical Temperature Gradient.

Abstract: Organic thermoelectric (TE) composites and flexible devices have gained a rapid development in recent decade. Herein, a flexible and foldable film of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)/single-walled carbon nanotube (PEDOT:PSS/SWCNT) composite is fabricated by post-treatment with an ionic liquid (IL), and an S-shape TE generator (TEG) is designed to harvest heat from human body via a vertical temperature gradient. After being post-treated with IL of bis(trifluoromethane)sulfonimide lithium salt (LiTFSI), the PEDOT:PSS/SWNCT composite displays an improved electrical conductivity from 1063 ± 80 to 1562 ± 170 S cm-1, with an almost constant Seebeck coefficient of ∼21.9 μV K-1 with a 30 wt % content of SWCNT. The TE properties exhibit excellent stability against repeated bending or folding cycles. Furthermore, an S-shape architecture is designed for TEG assembling, which enables effective utilization of a vertical temperature gradient between the human body and surroundings. The present study proposes a universal strategy for harvesting heat using a wearable TEG via a vertical temperature gradient, which represents great prospects for application in self-powered wearable electronics.

Recent advances in solution assisted synthesis of transition metal chalcogenides for photo-electrocatalytic hydrogen evolution.

Abstract: Hydrogen evolution from water splitting is considered to be an important renewable clean energy source and alternative to fossil fuels for future energy sustainability. Photocatalytic and electrocatalytic water splitting is considered to be an effective method for the sustainable production of clean energy, H2. This perspective especially emphasizes research advances in the solution-assisted synthesis of transition metal chalcogenides for both photo and electrocatalytic hydrogen evolution applications. Transition metal chalcogenides (CdS, MoS2, WS2, TiS2, TaS2, ReS2, MoSe2, and WSe2) have received intensified research interest over the past two decades on account of their unique properties and great potential across a wide range of applications. The photocatalytic activity of transition metal chalcogenides can further be improved by elemental doping, heterojunction formation with noble metals (Au, Pt, etc.), non-chalcogenides (MoS2, In2S3, NiS1-X), morphological tuning, through various solution-assisted synthesis processes, including liquid-phase exfoliation, heat-up, hot-injection methods, hydrothermal/solvothermal routes and template-mediated synthesis processes. In this review we will discuss recent developments in transition metal chalcogenides (TMCs), the role of TMCs for hydrogen production and various strategies for surface functionalization to increase their activity, different synthesis methods, and prospects of TMCs for hydrogen evolution. We have included a brief discussion on the effect of surface hydrogen binding energy and Gibbs free energy change for HER in electrocatalytic hydrogen evolution.

Tuning plasmonic p–n junction for efficient infrared-light-responsive hydrogen evolution

Abstract: Infrared (IR) light, which occupies almost half of all solar energy has been an untapped energy source up to date. The solar fuel production using the IR region of light hold the key to full utilization of solar energy. The localized surface plasmon resonance (LSPR), which is tunable by the size, composition, doping ratios, is a promising phenomenon realizing the light-harvesting ability in the IR region. Here, we report the IR-responsive photocatalyst composed of CdS and plasmonic Cu 9 S 5 , which break the record of IR-light induced photocatalytic hydrogen evolution reaction (apparent quantum yield = 4.4% at 1100 nm). Based on the simulation of the energy band at the p−n junction between plasmonic Cu 9 S 5 and CdS, the careful tuning of the CdS domain size archived the record-breaking photocatalytic activity. The optimization of the “plasmonic” p–n junction is a key for a highly efficient IR-responsive photocatalyst. The IR-responsive photocatalysts composed of cadmium sulfide (CdS) and plasmonic copper sulfide (Cu 9 S 5 ) break the record of IR-light induced photocatalytic hydrogen evolution reaction (apparent quantum yield = 4.4% at 1100 nm), which could be tuned by the built-in potential and acceptor CdS size domain in the plasmonic p−n junction. • The plasmonic IR-responsive photocatalysts break the record of IR-light induced photocatalytic hydrogen evolution reaction (HER). • The built-in potential and acceptor CdS size domain in the plasmonic p−n heterojunction play the key for HER. • Femtosecond time-resolved transient absorption demonstrated that the near infrared light induced hot electron transfer from plasmonic Cu 9 S 5 to CdS, which made the “plasmonic” p−n junction at interfaces with optimization for a highly efficient IR-responsive photocatalyst.