Fuqiang Liu

University of Massachusetts Lowell | UML · Department of Mechanical Engineering

Electrochemical impedance spectroscopy (EIS) is considered a quick and nondestructive diagnostic tool to characterize the degradation of lithium-ion batteries within a short testing timeframe. In this study, to obtain the relationship between EIS spectra and cell capacity degradation, our previously reported physics-based EIS model is further utili...

Solid-state perovskite solar cells are increasingly being studied for their relatively low material processing cost, high solar absorption coefficient, and promising power conversion efficiency. However, the major hurdles preventing commercialization of these devices, typically consisting of a perovskite light absorber sandwiched between electron a...

The future of sustainable energy will consist of renewable energy integration with the critical enabler-energy storage technologies such as batteries. Specifically, redox flow batteries represent one type of grid-scale energy storage device with long life spans of at least 10 years and capabilities like peak shaving and load leveling. As more exper...

In recent years, there has been an increased interest in hydrogen energy due to a desire to reduce greenhouse gas emissions by utilizing hydrogen for numerous applications. Some countries (e.g., Japan, Iceland, and parts of Europe) have made great strides in the advancement of hydrogen generation and utilization. However, in the United States, ther...

Among several types of redox flow batteries (RFBs) under development, non-aqueous redox flow batteries (NRFBs) have the potential to approach the energy density of lithium-ion batteries, while maintaining the advantages of flow systems, including ability to decouple power and energy ratings, and thermal stability. Despite their promise, NRFBs suffe...

Nondestructive, quick, and accurate diagnosis of lithium-ion batteries are critical tools to extend battery lifetime and ensure safe operation under complicated real-time power demand conditions. In this study, an electrochemical characterization approach coupling impedance spectroscopy with a physics-based model (EIS-Physical) has been demonstrate...

Microscale computed tomography scans of fiber-reinforced composites reveal that fibers are most often not strictly parallel to each other but exhibit varying degrees of misalignment and entanglement. One characteristic of this entanglement is the degree to which fibers stay together as clusters. In this study, a method for identifying and isolating...

Solar energy can be stored via either an indirect route in which electricity is involved as an intermediate step, or a direct route that utilizes photogenerated charge carriers for direct solar energy conversion. In this study, we investigate the fundamental difference between the direct and indirect routes in solar energy conversion using a new ph...

Large scatter of bulk composite properties is linked to the process-induced microstructural variations during composite manufacturing. It is hypothesized that quantification and virtual reproduction of these process-induced variations in the composite microstructure can highlight the effect of processing conditions on the composite microstructure a...

Due to inherent intermittency nature of light, energy must be stored within external batteries in photovoltaic systems, resulting in systems that are fragile and expensive. Internal storage integration can offer highly robust systems at substantially low cost if external batteries are replaced by internal ones. Despite excellent photovoltaic power...

Electrochemical carbon dioxide conversion to more valuable products such as formate (its protonation leads to formic acid, a versatile liquid fuel) is an appealing approach to mitigating the greenhouse gas emission and storing a surplus of renewable energy, but the catalysts developed to date are typically plagued by rapid deactivation. Catalyst de...

The development of Li-ion battery management systems (BMSs) is highly dependent on high fidelity computer simulations. In traditional physics-based models (PBMs), Fick’s law coupled with the Butler–Volmer equation has been employed to describe both Li-ion diffusion and solid/liquid interfacial Li-ion intercalation/deintercalation, but this methodol...

In situ Raman spectroscopy was employed to probe Li-ion concentration in liquid electrolytes at the cathode LiFePO4 particle surface in an optically transparent lithium ion battery. A Raman laser beam size of 2 μm was utilized so that Li-ion transport dynamics at the particle-level could be revealed. The variation of Li+ concentration in the LiPF6/...

Long-term performance and lifetime of vanadium redox flow batteries (VRFBs) are critical metrics in widespread implementation of this technology. One challenging issue that negatively affects these parameters is the faradaic imbalance, which is not comprehensively investigated in the literature. Faradaic imbalance is known as the shift in the avera...

Perovskite solar cells (PSCs) are remarkably efficient. Recent years have witnessed a surge in PSC researches in both material development and structure optimization. In a PSC, a lead halide perovskite absorber is typically sandwiched between layers of hole and electron transport materials (i.e., HTM and ETM, respectively) to facilitate the extract...

Vertically aligned one-dimensional (1D) materials offer numerous advantages for photoelectrochemical (PEC) energy conversion due to highly accessible surface area, direct charge transport pathway along the aligned direction, and suppressed electron-hole recombination. Hierarchical 1D-2D materials generate heterogeneous interfaces that can modify in...

Greater levels of solar energy storage provide a promising path for sustainable and reliable utilization of the renewable energy source. One of the greatest challenges towards large-scale implementation of this technology is improving storage capacity and efficiency. The conventional solar-storage architecture, where rechargeable batteries and sola...

Greater levels of solar energy storage provide an effective solution to the inherent nature of intermittency, and can substantially improve reliability, availability, and quality of the renewable energy source. Here we demonstrated an all-vanadium (all-V) continuous-flow photoelectrochemical storage cell (PESC) to achieve efficient and high-capacit...

Photoelectrochemical (PEC) devices, which use solar energy to drive charge transfer, have been considered as a low cost and effective approach to harvest energy from the sun. Dye sensitization designs are promising alternative to traditional semiconductor-based cells, as they can absorb a wide spectrum of light and provide free energy for PEC react...

Fundamental understanding of vanadium ion transport and the detrimental effects of cross-contamination on vanadium redox flow battery (VRFB) performance is critical for developing low-cost, robust, and highly selective proton-conducting membranes for VRFBs. The objective of this work is to examine the effect of conductivity and diffusivity, two key...

Application of nanostructured materials in electrochemical and photoelectrochemical devices could yield a dramatic improvement in energy storage, conversion, and generation efficiency because they dramatically alter the surface reaction rates and charge transport throughout the materials. In this work, one-dimensional TiO2 nanobelts have been explo...

Conductive biodegradable materials are of great interest for various biomedical applications, such as tissue repair and bioelectronics. They generally consist of multiple components, including biodegradable polymer/non-degradable conductive polymer/dopant, biodegradable conductive polymer/dopant or biodegradable polymer/non-degradable inorganic add...

Direct capture and storage of abundant but intermittent solar energy using storage devices are of paramount importance in development of sustainable energy, yet the daunting challenge is to enhance the conversion efficiency. Here we report an all-vanadium (all-V) photoelectrochemical storage cell (PESC) using geometry-enhanced ultra-long TiO2 nanob...

Biodegradable conductive polymers are currently of significant interest in tissue repair and regeneration, drug delivery and bioelectronics. However, biodegradable materials exhibiting both conductive and elastic properties have rarely been reported to date. To that end, an electrically conductive polyurethane (CPU) was synthesized from polycaprola...

With a demonstrated high Faradaic efficiency of 95%, an all-vanadium (all-V) photoelectrochemical storage cell (PESC) has been deemed as a promising candidate for efficiently capturing and storing solar energy.(1, 2) In this work, we further enhanced photocurrent of the existing all-V PESC by 5X by utilizing forced convective transport of the react...

Unique morphology-tunable Au/Pd core–shell nanoparticles were synthesized by galvanic replacement of preformed Cu on hollow Au cores using different PdCl2 concentrations. The nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electrochemical analysis. The...

A series of bimetallic PdxRuy/C (x:y = 4:1, 2:1, 1:1, and 1:2) nanoparticles have been synthesized by reducing PdCl2 and RuCl3 on carbon support by sodium borohydride for electrochemical oxidation of formic acid. Particularly, the extent of PdRu alloying was intentionally kept low and constant (around 2%) in order to understand the effect of Ru com...

Positive electrode materials in a lithium-ion battery play an important role in determining capacity, rate performance, cost, and safety. In this chapter, the structure, chemistry, thermodynamics, phase transition theory, and stability of three metal oxide positive materials (layered, spinel, and olivine oxides) are discussed in detail. In addition...

Guanidinium based blend anion exchange membranes (AEMs) for direct methanol alkaline fuel cells have been fabricated and studied. The guanidinium prepolymer is first synthesized through a simple polycondensation process with the ion exchange moieties incorporated directly into the polymer backbone, and then is used to make guanidinium - chitosan (G...

While Li-ion cells offer excellent electrochemical performance for several applications including electric vehicles, they also exhibit poor thermal transport characteristics, resulting in reduced performance, overheating and thermal runaway. Inadequate heat removal from Li-ion cells originates from poor thermal conductivity within the cell. This pa...

The properties of a supporting electrolyte are critically important to any photo- or electrochemical cells. In this study, we conducted studies on and characterized an all-vanadium photoelectrochemical storage cell (all-V PESC) for highly efficient solar energy storage using methanesulfonic acid (MSA) as a promising supporting electrolyte. Linear s...

Solar energy conversion and storage by photoelectrochemical cell (PEC) have been undertaken colossal studies in the past four decades. However, how to efficiently utilize solar energy despite of intermittent nature of sunlight still remains a challenge. In this paper, a WO 3 /TiO 2 hybrid photoelectrode was coupled with our newly-developed all-vana...

An all-vanadium redox photoelectrochemical cell with a carbon coated TiO2 photoelectrode was designed to convert/store solar energy as a promising alternative to photogeneration of hydrogen. In this study, a facile high-temperature sintering approach was employed to tailor the amount of the carbon coating at the TiO2 photoanode. Considerable enhanc...

Solar energy conversion and storage by photoelectrochemical cell (PEC) have been undertaken colossal studies in the past four decades. However, how to efficiently utilize solar energy despite of intermittent nature of sunlight still remains a challenge. In this paper, a WO 3 /TiO 2 hybrid photoelectrode was coupled with our newly-developed all-vana...

The charge and discharge of lithium ion batteries are often accompanied by electrochemically driven phase-transformation processes. In this work, two in situ and operando methods, that is, micro-Raman spectroscopy and X-ray diffraction (XRD), have been combined to study the phase-transformation process in LiFePO4 at two distinct length scales, name...

Environmental pollution has been a severe issue for mankind and the immediate impact on our lives includes global warming as well as poor air quality. Besides, energy crisis attracts a lot concern as our demands for energy increase while the available energy resources are near depletion. A popular candidate that can be a solution for the above-men...

Commercial lithium-ion cells with the same LiCoO2/graphite electrodes were cycled at high-rate discharge, high-rate charge, and both high-rate charge and discharge until the capacity reached 60%. Periodic baseline characterization tests were performed including internal pressure, discharge capacity, and electrochemical impedance spectroscopy (EIS)....

A commercial lithium-ion cell with LiCoO2/graphite electrodes was cycled at high-rates (2C) at room temperature. Periodic measurements were performed including internal pressure measurement, discharge capacity, and electrochemical impedance spectroscopy (EIS). Poor cell cyclability was demonstrated with 39% capacity fade after 250 cycles. Both the...

A one-step and fast microwave technique was developed to synthesize graphene-supported TiN nanoparticles (TiN-G) directly from graphene and dihydroxybis (ammonium lactato) titanium (IV). During the synthesis graphene served as a reductant and template to reduce the Ti-precursor into TiN and then uniformly disperse TiN nanoparticles on it. Pt/TiN-G...

A highly-efficient all-vanadium photoelectrochemical storage cell has been demonstrated in this work. This storage cell takes advantage of fast electrochemical kinetics of vanadium redox couples of VO2+VO2+ and V3+/V2+, and appears as a promising alternative to photoproduction of hydrogen from water. Continuous photocharging for 25 h revealed a VO2...

Using a photoelectrochemical (PEC) cell to convert solar energy to either electricity or chemical fuels has attracted much attention in the last four decades. However, two major obstacles that hinder wide-spread application of this approach lie in the relatively wide bandgap of chemically stable semiconducotrs, e.g., TiO2, and the rapid recombinati...

Alkaline fuel cells potentially offer improved conversion efficiency and the prospect of using non-noble metal catalysts; however, low conductivity and fast degradation of anion exchange membranes (AEMs) prevent their widespread application. In this work, a series of novel composite AEMs were synthesized by incorporating guanidinium-based polymers...

Non-equilibrium phase transformation and effect of interfacial Li flux on miscibility gap in two-phase transformation of LiFePO4 have been explored in this study. Our previously developed "Mushy-Zone" (MZ) model, accounting for sluggish Li diffusion across the two-phase interface, has been employed to study the non-equilibrium phase transformation...

The Au/Pd core–shell nanoparticles (NPs) were synthesized via galvanic replacement of Cu by Pd on hollow Au cores by adding different concentrations of Na2SO3 solution. It was found that the higher concentration of Na2SO3 that was used, the rougher the Au nanospheres became. However, the rougher Au surface may cause more defects in the Pd layers an...

Au/Pd core-shell nanoparticles (NPs) were employed to study electro-oxidation mechanism of formate-based solutions. A series of combined studies including Raman spectroscopy, electrochemical stripping analysis, and computational simulations were conducted to understand electro-oxidation of formate-based solutions on the Au/Pd NPs. Compared to the c...

Over the past decade, the market for rechargeable Lithium-Ion batteries (LIB) has significantly grown to match the demands of consumer and commercial customers. Applications which require large storage capacity, high C charge and discharge rates, and long term cycling are of particular interest. Due to the long calendar and cycle life requirements...

Sub 10 nm Pdcore@Ptshell nanocrystals (NCs) were prepared by a facile and green reduction method in aqueous solutions using commercially available and nontoxic poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) amphiphilic triblock copolymers as the reductant, stabilizer, and capping agent. The growth mode and morphology of the Pt shel...

A facile method has been developed to synthesize Au/Pd core-shell nanoparticles via galvanic replacement of Cu by Pd on hollow Au nanospheres. The unique nanoparticles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, ultraviolet--visible spectroscopy, and electrochemical measurements. When...

The goal of this work is to study electrical transport within multiphase structures of Li-ion electrodes through numerical microstructure reconstruction and direct evaluation. Li-ion battery electrodes at different compositions were numerically reconstructed mimicking the experimental fabrication process. Electrode material agglomeration and interf...

LiFePO4 (LFP) based lithium-ion batteries possess high energy capacity and safety characteristics that are fundamentally superior to those made with other cathode materials. However, the undesired battery discharge capacity due to sluggish electronic and ionic transport in the orthorhombic olivine structure, especially at high rates, limits its wid...

Au-PtCu core-shell nanoparticles were successfully synthesized via galvanic replacement of Cu by Pt on hollow Au nano-spheres. Characterizations of the nanoparticles were conducted by X-ray diffraction (XRD), transmission electron microscopy (TEM), and electrochemical measurements. Results indicate 2-2.5 times higher specific activity and mass acti...

The photoresponse of bare TiO2 and TiO2/WO3 hybrid electrodes was studied in a photoelectrochemical cell with VO2+ in 3 M sulfuric acid as the electrolyte. Linear sweep voltammetry study on both electrodes under AM1.5 illumination revealed a significant photoresponse enhancement compared to photolysis of water. This is attributed to the hole scaven...

Unique Au/Pd core–shell nanoparticles were synthesized via galvanic replacement of Cu by Pd on hollow Au nano-spheres. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. The Au/Pd nanoparticles exhibit superior formic acid oxi...

Nanodendritic Ir@Pt core-shell bifunctional electrocatalysts were synthesized by a one-pot synthesis method for the first time. Besides good dispersion and uniform composition distribution, Ir@Pt bifunctional electrocatalysts have exhibited outstanding catalytic activity for both oxygen reduction and oxygen evolution reactions in comparison with th...

A quick and efficient approach to prepare nitrogen doped graphene (NG) is proposed in this paper via microwave heating in NH3 atmosphere. Results show that graphene, as an allotrope of carbon, is a good microwave-absorbing material and can reach a high temperature in minutes, facilitating nitrogen incorporation into the structure under NH3. Element...

We report a facile synthesis and characterization of highly-dispersed platinum nanoparticles supported on Ketjen carbon black (Pt/C) as electrocatalysts for polymer electrolyte membrane fuel fells (PEMFCs). Pt particles with size of ∼ 2.6 nm were synthesized through adsorption of Pt acetylacetonate on carbon supports and subsequently thermal decomp...

High-capacity Li-ion batteries are among the best candidates for next generation, clean, and potentially fossil fuels independent electric vehicles. One of the major challenges in Li-ion batteries is to improve mass transport across multiple phase interfaces within complex electrode structures. The goal of this work is to study the role of interfac...

The nonequilibrium phase transformation and particle shape effects in LiFePO4 materials of Li-ion batteries are explored in this work. A continuum model employing the "mushy-zone" (MZ) approach, accounting for sluggish Li diffusion across the two-phase boundary, has been developed to study the kinetically-induced nonequilibrium phenomenon in Li-ion...

Fundamental understanding of catalyst layer nanostructure of hydrogen polymer electrolyte membrane (PEM) fuel cells is critical for improvement in performance and durability. A process based 3D mathematical model has been developed to elucidate the effect of electrode composition, porosity and ionomer weight fraction in catalyst layers on electroch...

Journal of Power Sources j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j p o w s o u r a b s t r a c t Proper water management in a hydrogen-fueled polymer electrolyte membrane (PEM) fuel cell is critical for performance and durability. A mathematical model has been developed to elucidate the effect of thermal cond...

As a key parameter in enabling the operation of high concentration methanol fuel cells, the water transport coefficient through the membrane must be reduced to between 0 and -1/6. We show that this coefficient can be lowered to -0.7 at 60 degrees C and under common cathode flow conditions using fully humidified air. A previously developed membrane...

Various anode diffusion media have been experimentally studied to reduce water crossover in a direct methanol fuel cell (DMFC). A two-phase water transport model was also employed to theoretically study their effects on water transport and saturation level in a DMFC anode. It is found that wettability of the anode microporous layer (MPL) has a dram...

Recent fundamental studies have indicated the key requirement of low water crossover through the electrolyte membrane in order to enable the use of highly concentrated methanol in direct methanol fuel cells for portable electronics applications. In this paper, we shall demonstrate a single cell operated at 60oC with direct feed of methanol concentr...

This paper reports on an experimental approach to measuring the water crossover coefficient distribution for the first time. A straight-channel PEFC of 6cm2 segmented into 10 pieces along the reactant flow direction has been developed. The instrumented cell, combining the functions of current collection and gas sampling with one pin for each segmen...

The net water transport coefficient through the membrane, defined as the ratio of the net water flux from the anode to cathode to the protonic flux, is used as a quantitative measure of water management in a polymer electrolyte fuel cell (PEFC). In this paper we report on experimental measurements of the net water transport coefficient distribution...

A mathematical model for the cathode of a direct methanol fuel cell (DMFC) is developed to investigate two-phase transport in the catalyst layer (CL) and to elucidate the mechanism of cathode mixed potential due to oxidation of crossover methanol. A coupled model of two-phase species transport and multistep electrochemical kinetics, including simul...

The cathode catalyst layer in direct methanol fuel cells (DMFCs) features a large thickness and mass transport loss due to higher Pt loading, and therefore must be carefully designed to increase the performance. In this work, the effects of Nafion loading, porosity distribution, and macro-pores on electrochemical characteristics of a DMFC cathode C...