Single Direct Methanol Fuel Cell Research Articles

Effect of TiO2 and Al2O3 Addition on the Performance of Chitosan/Phosphotungstic Composite Membranes for Direct Methanol Fuel Cells.

Composite chitosan/phosphotungstic acid (CS/PTA) with the addition of TiO2 and Al2O3 particles were synthesized to be used as proton exchange membranes in direct methanol fuel cells (DMFCs). The influence of fillers was assessed through X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, liquid uptake, ion exchange capacity and methanol permeability measurements. The addition of TiO2 particles into proton exchange membranes led to an increase in crystallinity and a decrease in liquid uptake and methanol permeability with respect to pristine CS/PTA membranes, whilst the effect of the introduction of Al2O3 particles on the characteristics of membranes is almost the opposite. Membranes were successfully tested as proton conductors in a single module DMFC of 1 cm2 as active area, operating at 50 °C fed with 2 M methanol aqueous solution at the anode and oxygen at the cathode. Highest performance was reached by using a membrane with TiO2 (5 wt.%) particles, i.e., a power density of 40 mW cm-2, almost doubling the performance reached by using pristine CS/PTA membrane (i.e., 24 mW cm-2).

Light doping of tungsten into copper-platinum nanoalloys for boosting their electrocatalytic performance in methanol oxidation

Coupling the bi-functional mechanism with compressive lattice strain might be an effective way to boost the electrocatalysis of platinum (Pt)-based nanoparticles for methanol oxidation reaction (MOR). This strategy weakens the chemisorption of poisoning CO-like intermediates generated during MOR on the active Pt sites by lowering their d-band center. In this context, we herein report the synthesis of ternary copper-tungsten-platinum (CuWPt) nanoalloys with light doping of W element by simply co-reducing their precursors at elevated temperature. In this ternary alloy system, the presence of only small amount of W element not only weakens the chemisorption of CO-like intermediates by lowering the Pt d-band center through compressive lattice strain, but also cleans the active Pt sites by "hydrogen spillover effect", endowing the as-prepared CuWPt nanoalloys at an appropriate Cu/W/Pt ratio with good activity for MOR. In specific, the ternary CuWPt alloy nanoparticles at a Cu/W/Pt molar ratio of 21/4/75 show a specific activity of 2.5 mA·cm⁻² and a mass activity of 2.11 A·mg⁻¹ with a better durability, outperforming those ternary CuWPt alloy nanoparticles at other Cu/W/Pt ratios, binary CuPt alloys and commercial Pt/C catalyst as well as a large number of reported Pt-based electrocatalysts. In addition, a single direct methanol fuel cell (DMFC) assembled using ternary CuWPt nanoalloys as anodic catalysts shows a power density of 24.3 mW·cm⁻² and an open-circle voltage of 0.6 V, also much higher than those of the single DMFC assembled from commercial Pt/C catalysts.

Effect of the Anode Structure on the Stability of a Direct Methanol Fuel Cell

The stability of a direct methanol fuel cell (DMFC) was investigated by two single DMFCs with different anode structure membrane electrode assembly (MEA) under discharging at the constant current m...

Palladized dysprosium fluoride nanorods as a new performance catalyst in direct methanol fuel cell

Fuel cells are a new type of batteries that produce electricity from a continuous source of alcohols as long as fuel is inserted. In this study, decorated palladium nanoparticles (PdNPs) on dysprosium fluoride (DyF3) nanorods (DyFNRs)-multiwalled carbon nanotubes (MWCNTs) were used for electrooxidation of methanol. DyFNRs were synthesized by the hydrothermal method, and the proposed multifunctional catalyst (DyFNRs/MWCNT-PdNPs) was identified by several methods such as X-ray diffraction, elemental mapping images, field emission scanning electron microscopy, energy dispersive analysis of X-rays, and transmission electron microscopy which demonstrated a uniform distribution and high dispersion of the PdNPs on the supports. The electrocatalytic activity toward methanol electrooxidation on glassy carbon electrode (GCE) with DyFNRs/MWCNT-PdNPs (DyFNRs/MWCNT-PdNPs/GCE) was investigated by cyclic voltammetry (CV) and chronoamperometry (CA). Experimental results showed a high improvement in oxidation potential and peak current of methanol electrooxidation by DyFNRs/MWCNT-PdNPs in comparison to DyFNRs and PdNPs. The values of the catalytic rate constant (k) and physical dimension (Ds) for methanol oxidation on the DyFNRs/MWCNT-PdNPs/GCE catalyst were calculated 0.008 s−1 and 1.43, respectively. Moreover, the order of reaction was determined to be 0.43 and 0.13 for CH3OH and NaOH, repectively. Finally, the synthesized catalyst was evaluated in direct methanol fuel cell (DMFC). The single DMFC with proposed anodic catalyst, DyFNRs/MWCNT-PdNPs, indicated a power density of 4.4 mW·cm−2 at a current density of 18 mA·cm−2 in alcohol (1 M) and NaOH (1 M).

Effect of NH3 Etching on Fe-N-C Catalyst for Oxygen Reduction Reaction in Direct Methanol Fuel Cell

Globally, because of the consumption of fossil fuel, the proton exchange membrane fuel cells (PEMFC) have received great attention. Direct methanol fuel cells(DMFC) have been applied into many fields, such as computers, global positioning systems(GPS) and portable devices. Platinum catalysts are considered as one of the most efficient catalysts for the oxygen reduction reaction(ORR),which is one of the most essential process for the DMFC. However, due to the high cost, the development of the DMFC calls for the non-precious metal catalyst, such as the Fe-N-C catalyst. We report a process to synthesize a Fe-N-C catalyst. Firstly, 80 ml 1.5M HCl, 2 ml aniline, 3 ml cyanamide, and 3 g ferric chloride were fixed and stirred for 20 min, with 5 g (NH4)2S2O8 dissolved into 80 ml 1.5M HCl dropped slowly. The mixture after being stirred for 4 h was mixed with the BP2000 carbon black dissolved into 80 ml 1.5M HCl for 40 min. Secondly,the mixture was heated at 80 degrees and stirred at 300rpm until dried. After being boiled in 2M H2SO4 for 5 h at 90 ℃ and milled at 400rpm for 3h, the sample was filtered and dried. Finally, half of the precursor was calcined for 2.5 h in N2, and 0.5 h in NH3 at 900℃, and the others were calcined in N2 for 3 h. After being heated for 5 h in 0.5 M H2SO4 at 90℃, and calcined for 3 h in N2 at 900℃ to gain the catalyst. The catalysts were named Fe-N-C00 and Fe-N-C30 separately. For RDE and RRDE tests on the Fe-N-C catalyst, the ink was prepared by mixing 15mg catalyst dissolved into 525µl ethanol and 145µl Nafion, which was stirred for 40min to achieve a good dispersion. 7µl ink was coated on the surface of RDE, making the loading of the catalyst 800µg cm-2. The staircase voltammetry(SCV) tests were conducted at the speed of 1600rpm in O2-saturated 0.5M H2SO4 solution. The half-wave of the potential of Fe-N-C00 catalysts were about 20mV lower than Fe-N-C30(0.685V vs 0.705V). According to the Koutecky-Levich equation, we calculated the electron transfer number was 3.97, and the productivity of H2O2 was 1.3%, which proved a four-electrons transfer process. The Fe-N-C catalyst used as the cathodic catalyst,which was sprayed onto a carbon paper gas diffusion(GDL,SGL 29BC), was applied into a single DMFC. A Nafion® 117 membrane from Dupont worked as the electrolyte. The membrane was pre-treated following a standard procedure before use. A commercial Pt-Ru (30% Pt-Ru/C)catalyst was used as anodic catalyst.The anode gas diffusion electrode (GDE), the cathode GDE and the membrane were put together in sequence and hot-pressed by 135℃and 5MPa for 5 min to form a MEA separately. The loading of the catalysts including Fe-N-C and Nafion was 4mg cm-2,and the ratio of the Fe-N-C catalyst was 55%. The polarization curve of the DMFC with the different MEA was tested to reflect the effect of Fe-N-C00 and Fe-N-C30 catalyst on DMFC. Figure 1

Performance of passive DMFC with expanded metal mesh current collectors

This article assesses the feasibility of the expanded metal mesh as the current collector in the passive direct methanol fuel cell (DMFC). A single passive DMFC fixture is designed and fabricated. An acrylic supporting plate is incorporated in the cell fixture for compressing the EMCC against MEA to achieve a proper contact between the MEA and expanded metal mesh current collector (EMCC). The performance of the passive DMFC is carried out and compared with different combinations of the supporting plates and EMCCs. For this purpose, open circuit voltage, the polarization test, and electrochemical impedance spectroscopy are conducted. It is found that the configurations of the supporting plate affect the performance of the cell, and the maximum performance can be achieved by optimizing its open ratio by varying the rib configuration and rib thickness. The results reveal that the passive DMFC with EMCC gives better performance as compared to the conventional passive DMFC with circular perforated current collector and the EMCC also facilitates more fuel spreading at anode catalyst layer and increases operating temperature. Furthermore, it is seen that the mesh type and geometry of the EMCC affect the cell performance, and the passive DMFC with the coarse mesh, wider strand width and thicker EMCC produce better cell performance.

A gradient activation method for direct methanol fuel cells

To realize gradient activation effect and recover catalytic activity of catalyst in a short time, a gradient activation method has firstly been proposed for enhancing discharge performance and perfecting activation mechanism of the direct methanol fuel cell (DMFC). This method includes four steps, i.e. proton activation, activity recovery activation, H2-O2 mode activation and forced discharging activation. The results prove that the proposed method has gradually realized replenishment of water and protons, recovery of catalytic activity of catalyst, establishment of transfer channels for electrons, protons, and oxygen, and optimization of anode catalyst layer for methanol transfer in turn. Along with the novel activation process going on, the DMFC discharge performance has been improved, step by step, to more than 1.9 times higher than that of the original one within 7.5h. This method provides a practicable activation way for the real application of single DMFCs and stacks.

A poly(vinyl alcohol)-based composite membrane with immobilized phosphotungstic acid molecules for direct methanol fuel cells

Phosphotungstic acid (H3PW12O40, HPW) molecules were anchored onto carbon nanotubes (CNTs) by electrostatic self-assembly using poly(diallyldimethylammonium chloride) (PDDA); subsequent incorporation of these particles into poly(vinyl alcohol) (PVA) afforded a methanol-blocking membrane for direct methanol fuel cell (DMFC) application. The prepared membrane exhibited a significantly higher proton conductivity of 9.4mScm−1 at 60°C and satisfactory proton conductivity stability over a 120-h test than a PVA membrane. Moreover, the composite membrane showed a decrease in the methanol permeability by ∼40% compared to a PVA membrane (6.10×10−7cm2s−1) and much better proton-to-methanol selectivity because of a higher dimensional stability after the incorporation of CNTs. A single DMFC based on the prepared membrane exhibited a maximum power density of 16mWcm−2 at 60°C. Thus, CNT-PDDA-HPW/PVA membranes have a great potential as an alternative proton exchange membrane for DMFC application.

Systemic modeling and analysis of DMFC stack for behavior prediction in system-level application

In this paper, a systemic model based on the equivalent circuit modeling method is developed in order to analyze the electrical behavior of direct methanol fuel cell (DMFC) stack in complex systems. The systemic model consists of the polarization curve subsystem, the long time discharge subsystem, and the temperature distribution of catalyst layer subsystem. The effect of various operating parameters on the behavior of the DMFC stack is evaluated by the systemic model. In addition, the systemic model is applied to design a DMFC stack with 4 single DMFCs connected in series. The simulated current-power profiles and time-power profiles are validated by the experimental results of the designed DMFC stack. Numerical results such as the effect of assembly pressure and the temperature distribution of catalyst layer are also discussed. Based on the numerical results, the most appropriate assembly pressure for the DMFC stack is 1.5 MPa. The total energy released at the current of 400 mA is the maximum according to both the simulated and experimental results. This systemic model provides a meaningful method to design DMFC stacks in the view of the system-level.

Sulfonated poly(ether ether ketone)-based hybrid membranes containing graphene oxide with acid-base pairs for direct methanol fuel cells

The graphene oxide (GO) sheets are functionalized by histidine molecules and incorporated into sulfonated poly (ether ether ketone) (SPEEK) matrix to fabricate hybrid polymer electrolyte membranes for direct methanol fuel cells (DMFCs). The loading of functionalized GO is varied to investigate its influence on cross-sectional morphology, crystalline structure, polymer chain stiffness, thermal stability and fractional free volume of membrane, etc. The acidic −SO3H groups (proton donors) in SPEEK and basic imidazole groups (proton acceptors) in histidine molecules form acid-base pairs and transport protons synergistically, thus yielding efficient proton channels inside the hybrid membranes. The maximum proton conductivity (at 100% RH) of hybrid membranes is elevated by 30.2% compared with the plain SPEEK membrane at room temperature. The functionalized GO flakes also confer the hybrid membranes low methanol permeability in the range of 1.32–3.91×10−7cm2s−1. At the filler content of 4wt%, the hybrid membrane shows a superior selectivity of 5.14×105Sscm−3 and its maximum power density of single DMFC cell (43.0mWcm−2) is 80.7% higher than that of plain SPEEK membrane.

An Equivalent Circuit Model of Direct Methanol Fuel Cell for Polarization Analysis

This paper presents a gray-box equivalent circuit model (ECM) in order to predict the performance of direct methanol fuel cell (DMFC) unit. The ECM is composed of electronic components ranging from operational amplifier resistors to diodes. The current–voltage profiles and current–power profiles of this ECM are validated by the simulation results of the COMSOL model. Afterward, the influences of methanol concentration, operating temperature, and oxygen concentration on the performance of the single passive DMFC are all validated experimentally. All validations show that the ECM provides a good approximation of the behavior of the DMFC. In addition, a simulated application of a circuit system employing the ECM is explained. The simulated result is validated experimentally. This research makes it possible to analyze the behavior of a DMFC in real applications.

Nanostructured Transition Metal Nitride (MN) As a Potential Support for Pt(Ru) Anode Electro-Catalyst for Direct Methanol Fuel Cells (DMFCs)

The rapid depletion of fossil fuels and increased environmental pollution due to vast fossil-fuel consumption is a thrust for efficient use of energy and exploration of renewable and clean energy sources.1 Generation of electricity from renewable energy sources, such as solar, wind without producing carbon dioxide-an undesired green house pollutant, offers enormous potential for meeting future energy demands. In this direction, fuel cell technology has gained special attention as it provides promising and sustainable approach for the production of continuous power with reduced greenhouse gas emissions and higher efficiencies compared to combustion based technologies. In particular, direct methanol fuel cells (DMFCs) have got attention as power sources due to advantages like use of methanol as fuel which has higher energy density (3800 kcal/l) than hydrogen (658 kcal/l, used as a fuel in proton exchange membrane fuel cells), safety and ease of handling the fuel (than H2) and low operating temperature. This offers quick start-up and extended durability of system components. The simple system design would be reflected as an ease in operation, reduced cost and high reliability. Hence, they are considered to be an ideal energy source for applications like automobile, portable devices, stationary systems, etc.2One of the major constraints in the development of high performance DMFCs is the low power density of the system due to poor catalytic performance at the electrodes and high capital cost due to use of expensive noble metal electro-catalysts. Hence, it is important to explore new electro-catalyst with reduced noble metal content at both anode and cathode to enhance the efficiency and power density of DMFC. Currently, Pt(Ru) alloy has been identified as a most active anode electro-catalyst for methanol electro-oxidation in DMFC. The synthesis of high surface area Pt(Ru) electro-catalyst is important to improve the reaction kinetics. In addition, efficient utilization of electro-catalyst by achieving high electrochemical active surface area is important, which can be accomplished by dispersing Pt(Ru) electro-catalyst on support with high surface area and superior electrical conductivity. The present study explores highly conductive nanostructured transition metal nitride (MN) as a potential support for Pt(Ru) electro-catalyst for methanol eletcro-oxidation. High surface area Pt(Ru)/MN (~125 m2/g) has been synthesized by wet chemical approach employing non-halide precursors of Pt and Ru. The electrochemical characterization has been carried out in 1 M methanol and 0.5 M sulfuric acid, used as fuel and electrolyte, using Pt wire as counter electrode and Hg/Hg2SO4 as reference electrode (+0.65 V with respect to NHE) and Pt loading of 0.3 mg/1cm2 at 400C. Pt(Ru)/MN shows promising performance for methanol oxidation, showing ~52% improved catalytic activity at ~0.65 V (vs NHE) in half-cell configuration and ~56% higher maximum power density in single DMFC study (Fig. 1) than that of commercial JM-Pt(Ru). This is attributed to well-dispersion of Pt(Ru) on MN (support of surface area of ~125 m2/g) offering high utilization of noble metals Pt and Ru, along with superior electrochemical active surface area and low charge transfer resistance for Pt(Ru)/MN than that of JM-Pt(Ru). Pt(Ru)/MN also shows superior electrochemical stability in half-cell configuration and single DMFC study than JM-Pt(Ru) electro-catalyst. Thus, the present study demonstrates the potential of MN as a support in improving the electrochemical activity of Pt(Ru) electro-catalyst, in the aim of achieving superior electrochemical performance and stability with reduced noble metal content for the electro-catalyst of DMFC. This portends significant reduction in the overall capital cost of DMFC system. Results of the synthesis, structural characterization and electrochemical activity of these electro-catalysts will be presented and discussed.

Investigation of MEA degradation in a passive direct methanol fuel cell under different modes of operation

Direct methanol fuel cell (DMFC) durability tests were conducted in three different operational modes: continuous operation with constant load (LT1), on–off operation with constant load (LT2) and on–off operation with variable load (LT3). Porous carbon nanofiber (CNF) anode layers were employed in three sets of single passive DMFCs; each membrane electrode assembly (MEA) was run continuously in durability testing for 3000h. The objective of this study is to investigate the degradation mechanisms in an MEA with a porous CNF anode layer under different modes of operation. The polarization curves of single passive DMFCs before and after durability tests were compared. The degradation of DMFC performance under the cyclic LT1 mode was much more severe than that of LT2 and LT3 operation. The loss of maximum power density after degradation tests was 49.5%, 28.4% and 43.7% for LT1, LT2 and LT3, respectively. TEM, SEM and EDS mapping were used to investigate the causes of degradation. The lower power loss for LT2 was mainly attributed to the reversible degradation caused by poor water discharge, which thus reduced the air supply. Catalyst agglomeration was especially observed in LT1 and LT3 and is related to carbon corrosion due to possible fuel starvation. The loss of active catalyst area was a major cause of performance degradation in LT1 and LT3. In addition to this, the dissolution and migration of Ru catalyst from the anode to cathode was identified and correlated with degraded cell performance. In the DMFC, the carbon nanofiber anode catalyst support exhibited higher performance stability with less catalyst agglomeration than the cathode catalyst support, carbon black. This study helps understand and elucidate the failure mechanism of MEAs, which could thus help to increase the lifetime of DMFCs.

Oxygen starvation induced cell potential decline and corresponding operating state transitions of a direct methanol fuel cell in galvanostatic regime

Air maldistribution is frequently encountered in direct methanol fuel cell (DMFC) stacks. To understand the characteristics of different single cells at air maldistribution, the effect of the oxygen stoichiometry (OS) on the behavior of a single DMFC in galvanostatic operation is investigated both experimentally and numerically. Special attention is paid to the cell potential dependence on the OS, based on which the OS is characterized into three distinct ranges. The cell potential varies little in range 1, but decreases dramatically with the OS in range 2, and becomes negative in range 3. The cell characteristics in each range are highlighted in detail. The entire cell acts as a normal DMFC in range 1, but turns to bi-functional mode in range 2 with parasitic hydrogen evolution from the negative electrode (NE) due to partial oxygen depletion. Extremely high current density arises near the air inlet when the cell potential approaches zero, which can lead to high electrode potential in the NE and induce serious ruthenium dissolution. When the OS decreases further to range 3, hydrogen evolution starts to occur in the positive electrode (PE), and the evolved hydrogen can be re-oxidized upstream, leading to coexistence of four electrochemical half-reactions in the PE.

Behavior of a Single Direct Methanol Fuel Cell in Stacks at Air Maldistribution Conditions

The air maldistribution through different individual cells is frequently encountered in direct methanol fuel cell (DMFC) stacks since most stacks utilize parallel flow configuration. This air maldistribution has been recognized as one of the most important causes for the performance loss and even durability loss of DMFC stacks. To better understand the impact of air maldistribution, the behavior of a single DMFC at various air flow rates (AFRs) is investigated both experimentally and numerically. Special attention is paid to the variation of cell voltage with AFR. It is found that the cell voltage drops significantly when the AFR decreases below a critical value. With the further drop of AFR, the cell voltage descends more sharply and even becomes negative at ultralow AFRs. The reasons for this unique behavior of cell voltage with AFR are explored in detail within this work.

Novel O2-enhanced methanol oxidation performance at Pt–Ru–C sputtered anode in direct methanol fuel cell

We have developed a novel anode catalyst for the direct methanol fuel cell (DMFC). A Pt–Ru–C electrode was prepared by a co-sputtering technique and compared with Pt and Pt–Ru sputtered electrodes for the methanol electro-oxidation reaction. The prepared Pt–Ru–C electrode with a specific atomic ratio showed a remarkable O2-enhanced methanol oxidation performance by O2 addition to methanol as a fuel. For practical utilization, the relationship between the O2-enhanced methanol oxidation activity and the thermal stability of the Pt–Ru–C sputtered electrode was evaluated using a post-annealing treatment. It is found that the O2-enhanced methanol oxidation activity of the Pt–Ru–C electrodes is retained if the annealing temperature is less than or equal to 100 °C. Finally, the DMFC performance was assessed using a single DMFC cell incorporating a membrane electrode assembly with Pt–Ru–C which was hot-pressed at 100 °C. The O2-enhanced methanol oxidation was observed at a single DMFC cell also. Moreover, the enhanced reaction was recognized in DMFC power generation by feeding methanol and oxygen to the anode and oxygen to the cathode.

O2-Enhanced Methanol Oxidation at Pt-Ru-C Ternary Sputtered Electrode

We have developed a novel anode catalyst for the direct methanol fuel cell (DMFC). Pt-C and Pt-Ru-C electrodes were prepared by a co-sputtering technique. These electrodes with a specific atomic ratio showed a remarkable O2-enhanced methanol oxidation performance and the reaction selectivity by O2 addition for methanol as a fuel. For practical utilization, the relationship between the O2-enhanced methanol oxidation activity and the thermal stability of the Pt-C and Pt-Ru-C sputtered electrodes were evaluated by a post annealing treatment. It is found that the O2-enhanced methanol oxidation activity of the Pt-Ru-C electrodes is retained if the annealing temperature is less than or equal to 100 C. Finally, the DMFC performance was assessed using a single DMFC cell incorporating a membrane electrode assembly with Pt-Ru-C which was hot pressed at 100 C.

Behavior of a Single Direct Methanol Fuel Cell in Stacks at Air Maldistribution Conditions

not Available.

Modified Nafion polymer electrolyte membranes by γ-ray irradiation used in direct methanol fuel cells

Modification of the commercial polymer electrolyte membrane (PEM) Nafion 117 by γ-ray irradiation to produce an improved proton exchange membrane for direct methanol fuel cells (DMFCs) was described. The Nafion 117 membrane was exposed under γ-ray irradiation circumstance with the irradiation doses from 103 to 105 Gy. Subsequently the properties of the membrane itself, in terms of swelling ratio, water uptake rate, proton conductivity and methanol permeability, together with the performance of its membrane electrode assembly (MEA) in DMFC were analyzed and contrasted with the untreated material. When the Nafion 117 membrane was exposed under γ-ray irradiation circumstance, the degradation and crosslinking reactions occurred at the same time. Specific scopes of the γ-ray irradiation dose may cause the membrane crosslinking, thus reduce the membrane swelling ratio and decrease the methanol crossover. By reducing the membrane swelling ratio and methanol permeation, the single DMFC with the modified Nafion 117 membrane produced reasonable power density performance as high as 32W/m2 under 2mol/L methanol solution at room temperature.

A 450-mV Single-Fuel-Cell Power Management Unit With Switch-Mode Quasi-${\rm V}^2$ Hysteretic Control and Automatic Startup on 0.35-$\mu$m Standard CMOS Process

This paper presents a power management unit (PMU) for emerging applications powered by low-voltage single direct methanol fuel cell (DMFC). A subthreshold startup scheme and its circuit implementation are proposed to enable low-voltage self-startup feature. A boost switching converter with a switch-mode, quasi-V2 hysteretic control is designed for power conditioning. The PMU is implemented on a standard 0.35-μm CMOS process with VTN/VTP of 0.55 V/ -0.75 V, respectively. Experimental results prove that the PMU automatically starts up with 450-mV single DMFC input. The output voltage of the PMU is well regulated with below 25 mV ripple. With an output power ranging from 20 to 200 mW, an average efficiency above 85.2% is obtained, with a maximum of 89.4%. Load transient recovery times are 11.6 μs/4.2 μs, respectively, in response to the step-up and step-down load changes between 10 and 100 mA.