Initial Current Density Research Articles

Stable and efficient hydrogen evolution activity of tungsten-incorporated nanocrystalline perovskite BaSnO3 electrocatalyst

The increasing demand in energy consumption and alarming environmental concern is compelling to develop alternative renewable and clean energy sources. Hydrogen (H2) is identified as a potential candidate due to its abundance, high gravimetric energy density, and no carbon footprint. Presently, splitting of water is a highly promising method for sustainable hydrogen generation, and the key challenge is to develop a stable and high-performing electrocatalysts for H2 evolution reaction (HER) as a renewable energy source. Metal oxides are excellent alternative electrocatalysts to noble metals due to their cost effectiveness, tunability and abundance. Ternary perovskite barium stannate (BaSnO3) has been intensely explored for water splitting and electrocatalysis related applications. Tungsten (W) 1 % incorporated BaSnO3 synthesized by facile hydrogen peroxide route is explored as an electrocatalyst for HER activity in acidic medium for the first time. The pure and W-incorporated BaSnO3 exhibited promising HER activity with an overpotential value of 233 and 295 mV at 10 mA/cm2 with enhanced electrochemical surface area of 7.309 and 3.075 Fcm−2, respectively. A 12-hour stability test not only concluded the durability and performance of H2 evolution activity but also confirmed the enhanced initial current density for the W-incorporated BaSnO3 sample.

N- and Ti3+-codoped TiO2 nanotube-modified SnO2-Sb electrode for the effective degradation of caprolactam wastewater

This study prepared the N- and Ti3+-codoped TiO2 nanotube-modified(TiON) SnO2-Sb electrode. The analysis of the surface topography, structure characteristics, chemical state, electrochemical characteristics of the interlayer and active layers reveals that the doped TiO2 nanotubes arrays exhibit superior electrical conductivity and a higher surface area, which facilitates the binding of enhanced antimony tin oxide(ATO) coating. Compared with TM/ATO electrode without TiON interlayer, stability and catalytic performance of the TM/TiON/ATO electrode were substantially enhanced, which improved by 32 % and nearly 10 times. Simultaneously, influence of initial pH and current density on the degradation effectiveness and electrical energy consumption were studied, and the failure mechanisms analysis of the electrode was analyzed. Research has demonstrated that TM/TiON/ATO exhibits both stability and efficiency, rendering it a highly favorable material for the anode.

Refractory organic matter removal from mature leachate by bipolar electrocoagulation-electrooxidation reactor configurations

In this study, mature leachate treatment with combined electrochemical processes was investigated to benefit from the advantages of electrocoagulation (EC) and electrooxidation (EO) simultaneously. First, control experiments were conducted, the most effective anode-cathode combination for EO was selected as Ti/IrO2-Gr, the number of Al electrodes for EC was determined as 3 and the number of Fe electrodes was determined as 5. Optimization of process parameters of the combined system with Al and Fe electrodes was conducted with Box-Behnken design (BBD). With BBD, the effect of the process parameters (initial pH, current density, and reaction time) on the system responses (COD, UV254, and color removal efficiencies) was determined. The suitability of the created model in the study was analyzed statistically and the results of quadratic models were found compatible with experimental studies. The model's capacity for prediction was also confirmed by validation experiments under optimum conditions. By implementing the optimum conditions, COD, UV254, and color removal efficiencies were determined as 71.5 %, 60.2 %, and 93.2 %, respectively for the combined process with Al electrodes and 79.5 %, 68.0 %, and 97.7 %, respectively for the combined process with Fe electrodes. Correlation of actual and predicted data showed that BBD is reliable for optimizing process parameters of combined processes with Al and Fe electrodes. The obtained results showed that combined processes are more effective than hybrid processes, based on both pollutant removal efficiencies and energy consumption.

Optimization and kinetic analysis of electrocoagulation-assisted adsorption for treatment of young landfill leachate

An investigation was conducted on the electrocoagulation treatment of high-strength young landfill leachate using an electrode made of aluminium in a batch electrochemical cell reactor. An iron sheet of 1 m⨯1 m⨯1.1 m (L: B: H) was used to construct the two landfill simulating reactors, both the reactors were operated at different conditions, i.e., one without rainfall (S1) and the other with rainfall (S2). Both reactors have 51% wet and 49% dry waste, which is the typical waste composition of India, and the quantity of waste taken was 450 kg; hence, the generated leachate was treated. This work focuses on the utilization of electrocoagulation as the sole treatment method where coagulation and adsorption occur simultaneously for young landfill leachate. The study employed a central composite design (CCD) to systematically vary the initial pH, current density (CD), and reaction time to examine their impact on the removal efficiency of COD (Chemical oxygen demand), TOC (Total organic carbon), and TSS (Total Suspended Solids). The optimum conditions obtained were a pH of 7.35, a CD of 15.29 mA/cm2, and a reaction duration of 57 min. When the conditions were optimized, the COD, TSS, and TOC removal efficiencies were 83.56%, 73.12%, and 85.58%, respectively. Also, the electrodes depleted 2.78 g of Al/L. In addition, pseudo-first-order and pseudo-second-order kinetics were employed to examine the elimination of contaminants by adsorption on aluminium hydroxide, thereby confirming the adsorption process. After investigation through energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD), with the produced sludge confirmed that electrocoagulation removed a significant amount of metals from landfill leachate.

Improved bacterial elimination in wastewater through electrocoagulation: hydrogen generation, adsorption of colloidal bacteria-flocks, and electric field bactericidal action

ABSTRACT Electrocoagulation (EC) has emerged as a promising method for wastewater treatment, offering efficient removal of various contaminants, including bacteria. This study investigates the mechanisms underlying bacterial removal in EC processes, mainly the hydrogen-mediated foam, the effect of operational parameters, including initial pH, current density, and reaction time, and evaluates the associated energy consumption. The EC reactor employed aluminum electrodes and operated at a current intensity of 3.0 A. It demonstrated a notable bacterial removal efficiency, with 120.102 UFC ml−1 of mesophyll floral aerobic bacteria removed through colloid bacteria-flocs precipitation, 440.102 UFC ml−1 via bacterial-bulls flotation from foam, and 117.102 UFC ml−1 through attraction at the electrodes’ plate surface. We found that the EC process leads to the formation of aluminum hydroxide and ferrous hydroxide precipitates, which adsorb bacteria and facilitate their removal from the wastewater via electrostatic forces with an energy consumption of 45 kWh/m3. Overall, this research provides valuable insights into the mechanisms governing bacterial removal in EC and highlights the importance of energy consumption analysis for optimizing wastewater treatment processes.

Synergistic Mo and W single atoms co-doped surface hydroxylated NiFe oxide as bifunctional electrocatalysts for overall water splitting

Two novel defect engineering strategies, surface hydroxylation and single atom (SA) doping, are explored to fabricate a high performance bifunctional water electrolysis catalyst, synergistic Mo and W SAs co-doped surface hydroxylated NiFe oxide (FN-MoWact). The product catalyst achieves ultralow overpotentials of 196 and 246 mV for oxygen evolution reaction (OER) and decent overpotentials of 79 and 246 mV for hydrogen evolution reaction (HER) at current densities of 10 and 500 mA cm−2, respectively. For overall water splitting, the FN-MoWact//FN-MoWact couple requires ultralow cell voltages of 1.504 and 1.729 V to deliver current densities of 10 and 500 mA cm−2, respectively, and remains stable after a 100-hour operation at an initial current density of 534 mA cm−2. The enhanced electrocatalytic activities are attributed to surface hydroxylation and doping of synergistic Mo and W SAs. The two defect engineering modifications, as supported by analyses of density functional theory calculations and in-situ X-ray absorption spectroscopy, lead to a proper reduction in metal-oxygen covalency, thus minimizing the energy difference of the rate-determining step of the OER process, and create surface active sites with a d-band center located closer to the Fermi level, thus properly strengthening proton binding to enhance HER activities.

Trading Off Initial PEM Fuel Cell Performance versus Voltage Cycling Durability for Different Carbon Support Morphologies

Tailored design of carbon supports and their pore morphologies is crucial to achieve the ambitious durability and performance targets for future proton exchange membrane fuel cells (PEMFCs). We compared platinum catalysts supported on solid Vulcan carbon, porous Ketjenblack carbon, and accessible porous modified Ketjenblack carbon in a voltage cycling-based accelerated stress test (AST) with frequent intermittent characterizations. We derived how catalyst morphologies affect cell performance and electrochemical properties (electrode roughness factor, ORR activity, oxygen transport resistances) at beginning-of-life (BoL) and in various states of degradation up to 200,000 voltage cycles. We confirmed the enhanced Pt surface area retention of porous carbon-supported catalysts, ascribed to well-shielded Pt particles in internal pores, but find that this comes at the expense of lower initial high current density performance already at BoL. Accessible porous carbon-supported catalysts with wider pores mostly retain those durability benefits while, simultaneously, maximizing H2/air performance at all current densities due to improved oxygen transport. We also tracked changes in catalyst accessibility throughout voltage cycling by analyzing local oxygen transport resistances and relative humidity-dependent platinum utilization. We propose that catalysts with porous carbon supports undergo oxidative pore opening, followed by continuous migration of internal Pt particles to the external carbon surface.

Synthesis and Electrocatalytic Performance Study of Sulfur Quantum Dots Modified MoS2.

The electrolysis of water for hydrogen production is currently receiving significant attention due to its advantageous features such as non-toxicity, safety, and environmental friendliness. This is especially crucial considering the urgent need for clean energy. However, the current method of electrolyzing water to produce hydrogen largely relies on expensive metal catalysts, significantly increasing the costs associated with its development. Molybdenum disulfide (MoS2) is considered the most promising alternative to platinum for electrocatalyzing the hydrogen evolution reaction (HER) due to its outstanding catalytic efficiency and robust stability. However, the practical application of this material is hindered by its low conductivity and limited exposure of active sites. MoS2/SQDs composite materials were synthesized using a hydrothermal technique to deposit SQDs onto MoS2. These composite materials were subsequently employed as catalysts for the HER. Research findings indicate that incorporating SQDs can enhance electron transfer rates and increase the active surface area of MoS2, which is crucial for achieving outstanding catalytic performance in the HER. The MoS2/SQDs electrocatalyst exhibits outstanding performance in the HER when tested in a 0.5 M H2SO4 solution. It achieves a remarkably low overpotential of 204 mV and a Tafel slope of 65.82 mV dec-1 at a current density of 10 mA cm-2. Moreover, during continuous operation for 24 h, the initial current density experiences only a 17% reduction, indicating high stability. This study aims to develop an efficient and cost-effective electrocatalyst for water electrolysis. Additionally, it proposes a novel design strategy that uses SQDs as co-catalysts to enhance charge transfer in nanocomposites.

Operando carbon corrosion measurements in fuel cells using boron-doped carbon supports

Carbonaceous materials are the most common catalyst supports in proton exchange membrane fuel cell (PEMFCs), yet their corrosion is one of the limiting factors in achieving high durability. Herein, we doped carbon supports with boron (B) to increase the corrosion-resistance of the support. Two types of B-doped carbons were synthesized and studied as platinum support materials. They varied in their morphologies, surface areas, and the types of boron species. The durability of Pt/B-doped carbon catalysts was investigated using the US-DOE catalysts’ supports accelerated stress test (AST) and a mass-spectrometer connected to the fuel cell effluent stream to quantify the mass of corroded carbon support in operando. The addition of boron to the carbon increased the stability of Pt catalysts in long-term usage of PEMFC. After 4000 AST cycles, more than 50 % of initial current density was preserved for the boron-containing systems, while less than 30 % of it remained with Vulcan carbon (Pt/V). Also, the Pt/B-doped carbon samples demonstrated better electrochemical active surface area (ECSA) stability when compared to Pt/V. Carbon loss measurements showed that B-doped carbons have higher resistance to electrochemical corrosion than unmodified carbon. Specifically, the substitutional boron-doped carbon demonstrated an extremely high stability and low corrosion rate.

Combined effects of annealing treatment and compounding with FeOOH cocatalyst on efficiency and stability of BiVO4/Ag3PO4 photoanode

Bismuth vanadate (BiVO4) is a promising metal oxide photoabsorber for photoanode applications but is limited by its relatively short hole diffusion length resulting in severe charge complexation and limited performance. Herein, Ag3PO4 was compounded on BiVO4 through photodeposition of Ag followed by solution oxidation. The annealing of the composite BiVO4/Ag3PO4 heterojunction at 400 °C precipitated some Ag from Ag3PO4 on BiVO4/Ag3PO4 to form a new ternary photoanode BiVO4/Ag3PO4/Ag. Compared to the unannealed sample, the light trapping and crystal quality enhanced, resulting in increased photocurrent density of the annealed BiVO4/Ag3PO4 photoanode (4.46 mA cm−2) by 59.9 % when compared to the unannealed photoanode (2.79 mA cm−2). To further optimize the photoanode, co-catalyst iron hydroxyl oxide (FeOOH) was deposited to yield BiVO4/Ag3PO4/Ag/FeOOH photoanode with maximum photocurrent density of 4.71 mA cm−2 at 1.23 V (vs. reversible hydrogen electrode, VRHE), equivalent to about 3.7-fold the value of BiVO4 photoanode. The photoanode maintained 90.8 % of its initial current density after 3 h stability tests. Besides, the photoelectrocatalytic degradation of Rhodamine B pollutant by BiVO4/Ag3PO4/Ag and BiVO4/Ag3PO4/Ag/FeOOH photoanode showed performance enhancement when compared to BiVO4/Ag3PO4. Overall, the proposed strategy looks very promising for the rational fabrication of high-efficiency heterojunction photoanodes.

Protective Properties of Calcareous Deposit Layer for Cathodically Polarized AH36 Steel in Natural Seawater

A calcareous deposit is a by-product of the cathodic polarization in seawater environments. This study presents the results of evaluating the anticorrosion and anti-macro-biofouling effectiveness of a calcareous deposit layer on the surface of the cathodically polarized AH36 structural steel in tropical seawater. The polarization is induced with initial current densities at which the calcareous deposit layer formed with both aragonite and brucite for 12 months continuously. The protective properties of the layer were compared with those of the passive layer from corrosion products under the same environmental conditions. The macro-biofouling in the tropical seawater is observed in the closed and open surfaces of the steel. The comparison of the anticorrosion property shows that, to some degree, the calcareous deposit layer contributes to surface passivation, as in the case of the corrosion product layer. In addition, the composition of the brucite and aragonite in the calcareous layer in the study plays a role as a macro-biofouling growth-limiting factor.

Analysis of the influence and mechanism of the pollution condensation environment on the electrochemical migration behaviour of printed circuit board with immersion silver

A refrigeration device was developed to induce condensation on printed circuit board with immersion silver (PCB-ImAg). Results show that in a condensation environment with low relative humidity, an electrolyte film can still be formed that allows conduction between the two poles of PCB-ImAg, allowing the thermodynamic conditions for electrochemical migration (ECM) to be reached and creating the risk of short-circuit failure. Under high relative humidity, the main body of ions that underwent ECM on the surface of PCB-ImAg was Cu2+ and as the relative humidity of the environment increases, the short-circuit failure time shortens, and the initial current density increases.

Simulation study of secondary electron multiplication on microwave dielectric window

The phenomenon of dielectric breakdown in microwave windows restricts the enhancement of power capacity in high-power microwave systems. This process starts with the secondary electron multiplication, which significantly influences the breakdown threshold. In this study, we developed 3D simulation models for rectangular, circular, and annular windows to examine the secondary electron multiplication on their surfaces using the particle-in-cell method. Through a comparative study, we assessed the effects of various input powers, initial emission current densities from particle sources, and magnetic fields. Our findings reveal that the initial field emission current density, which ranges from 10−9 to 109 μA/cm2, marginally affects electron multiplication. However, increased microwave power (with power density ranging from 0.1 to 18.75 MW/cm2) accelerates this multiplication. Strong magnetic fields and non-uniform electric fields further enhance the electron multiplication process.

Surface functionalization of nickel foam with two-dimensional conjugated MOFs Fe3(hexaiminotriphenylene)2 for highly efficient oxygen evolution reaction

The design of high-efficient, low-cost, and stable electrocatalysts for oxygen evolution reaction (OER) is highly demanding for energy conversion applications. Metal-organic frameworks (MOFs), with large surface area and flexible molecular species, can supply atom-dispersed metal active coordination sites (M−NX, M−SX, M−OX) for OER and have been regarded as potential catalysts for practical applications. However, it is still challenging to use MOFs as OER catalysts directly due to their low conductivity and poor stability. Herein, we successfully synthesized a 2D c-MOF of Fe3(HITP)2 (HITP = 2,3,6,7,10,11-hexaiminotriphenylene) on the surface of nickel foam (NF) by using a layer-by-layer self-assembly strategy. The Fe3(HITP)2/NF-x electrode (x = 5, 10, 15, 20 is the number of cycles) exhibited impressive OER catalytic activity in alkaline electrolyte (1 M KOH), which is superior or comparable to most of the transition metal-based materials reported. Typically, Fe3(HITP)2/NF-15 were able to fully expose the Fe-N4 catalytic sites with an overpotential of 224 mV at a current density of 10 mA·cm−2 and a Tafel slope of 45.4 mV·dec-1. This was mainly attributed to the higher ECSA value, better kinetic process, and fast charge transfer ability of Fe3(HITP)2/NF. In addition, the current density of Fe3(HITP)2/NF-15 remained at 97.3 % of the initial current density after 24 h i-t stability test, showing excellent catalytic stability. This work provided a novel design strategy for the direct application of MOFs to OER applications.

A hybrid system for Nickel ions removal from synthesized wastewater using adsorption assisted with electrocoagulation.

The presence of heavy metal ions in water environments has raised significant concerns, necessitating practical solutions for their complete removal. In this study, a combination of adsorption and electrocoagulation (ADS + EC) techniques was introduced as an efficient approach for removing high concentrations of nickel ions (Ni2+) from aqueous solutions, employing low-cost sunflower seed shell biochar (SSSB). The combined techniques demonstrated superior removal efficiency compared to individual methods. The synthesized SSSB was characterized using SEM, FT-IR, XRD, N2-adsorption-desorption isotherms, XPS, and TEM. Batch processes were optimized by investigating pH, adsorbent dosage, initial nickel concentration, electrode effects, and current density. An aluminum (Al) electrode electrocoagulated particles and removed residual Ni2+ after adsorption. Kinetic and isotherm models examined Ni2+ adsorption and electrocoagulation coupling with SSSB-based adsorbent. The results indicated that the kinetic data fit well with a pseudo-second-order model, while the experimental equilibrium adsorption data conformed to a Langmuir isotherm under optimized conditions. The maximum adsorption capacity of the activated sunflower seed shell was determined to be 44.247mg.g-1. The highest nickel ion removal efficiency of 99.98% was observed at initial pH values of 6.0 for ADS and 4.0 for ADS/EC; initial Ni2+ concentrations of 30.0mg/L and 1.5g/L of SSSB; initial current densities of 0.59mA/cm2 and 1.32 kWh/m3 were also found to be optimal. The mechanisms involved in the removal of Ni2+ from wastewater were also examined in this research. These findings suggest that the adsorption-assisted electrocoagulation technique has a remarkable capacity for the cost-effective removal of heavy metals from various wastewater sources.

Enzymolytic lignin derived Fe–N codoped porous carbon materials as catalysts for oxygen reduction reactions

Numerous active sites and hierarchical pore structures are important for improving catalytic performance for the oxygen reduction reaction (ORR). In this work, a series of iron-nitrogen-doped porous carbon materials (Fe–N–C) with ORR catalytic activity were prepared by a one-step pyrolysis method using enzymolytic lignin as the raw material, soy protein isolate and iron chloride as dopants. The results showed that the samples with the best performance have abundant Fe-Nx active sites and mesoporous structures. At the same time, the electrocatalytic results indicate that the half-wave potential of catalyst was 0.84 V, which reached 96.55% of commercial Pt/C catalysts (E1/2 = 0.86 V), it still preserves an initial current density of 92%, after 10,000 s of circulation, which is much better than Pt/C (86%). Due to the low cost, high activity and stable ORR property, the prepared non-precious metal electrocatalyst will play an important role in the applications of fuel cells.

Hierarchical PtCuMnP Nanoalloy for Efficient Hydrogen Evolution and Methanol Oxidation.

The higher amount of Pt usage and its poisoning in methanol oxidation reaction in acidic media is a major setback for methanol fuel cells. Herein, a promising dual application high-performance electrocatalyst has been developed for hydrogen evolution and methanol oxidation. A low Pt-content nanoalloy co-doped with Cu, Mn, and P is synthesized using a modified solvothermal process. Initially, ultrasmall ≈2.9 nm PtCuMnP nanoalloy is prepared on N-doped graphene-oxide support and subsequently, it is characterized using several analytical techniques and examined through electrochemical tests. Electrochemical results show that PtCuMnP/N-rGO has a low overpotential of 6.5 mV at 10 mA cm-2 in 0.3m H2SO4 and high mass activity for the hydrogen evolution reaction. For the methanol oxidation reaction, the PtCuMnP/N-rGO electrocatalyst exhibits robust performance. The mass activity of PtCuMnP/N-rGO is 6.790mA mg-1 Pt, which is 7.43 times higher than that of commercial Pt/C (20% Pt). Moreover, in the chronoamperometry test, PtCuMnP/N-rGO shows exceptionally good stability and retains 72% of the initial current density even after 20,000 cycles. Furthermore, the PtCuMnP/N-rGO electrocatalyst exhibits outstanding performance for hydrogen evolution and methanol oxidation along with excellent anti-poisoning ability. Hence, the developed bifunctional electrocatalyst can be used efficiently for hydrogen evolution and methanol oxidation.

The ultrathin regular circular structural Ni-P nanosheet for efficient urea electrooxidation

The direct urea fuel cell (DUFC) functions as a dual-purpose technology, serving as both a renewable energy production system and a means to degrade urea in wastewater. Herein, Ni-P nanosheets are synthesized using a chemical nickel-plating technique and applied to the urea oxidation reaction (UOR). The reaction time, plating solution pH, and reaction temperature play crucial roles in facilitating UOR kinetics. The optimized Ni-P nanosheets display good catalytic performance and the voltage difference between the 9000th and the first cycle is only 28 mV at 10 mA cm−2. Additionally, it maintains outstanding long-term stability at 1.52 V versus reversible hydrogen electrode (RHE) for 70 hours and Ni-P nanosheets deactivates by less than 1% compared to the initial current density, further confirming the high stability of Ni-P nanosheets for the UOR. This research not only offers a rapid and effective approach for developing advanced UOR catalysts but also introduces a conceptual framework for designing catalysts for various catalytic reactions.

Influence of the 3D architecture and surface roughness of SiOC anodes on bioelectrochemical system performance: a comparative study of freeze-cast, 3D-printed, and tape-cast materials with uniform composition

3D-printed anodes for bioelectrochemical systems are increasingly being reported. However, comparisons between 3D-printed anodes and their non-3D-printed counterparts with the same material composition are still lacking. In addition, surface roughness parameters that could be correlated with bioelectrochemical performance are rarely determined. To fill these gaps, slurries with identical composition but different mass fractions were processed into SiOC anodes by tape-casting, freeze-casting, or direct-ink writing. The current generation was investigated using electroactive biofilms enriched with Geobacter spp. Freeze-cast anodes showed more surface pores and the highest surface kurtosis of 5.7 ± 0.5, whereas tape-cast and 3D-printed anodes showed a closed surface porosity. 3D-printing was only possible using slurries 85 wt% of mass fraction. The surface pores of the freeze-cast anodes improved bacterial adhesion and resulted in a high initial (first cycle) maximum current density per geometric surface area of 9.2 ± 2.1 A m−2. The larger surface area of the 3D-printed anodes prevented pore clogging and produced the highest current density per geometric surface area of 12.0 ± 1.2 A m−2. The current density values of all anodes are similar when the current density is normalized over the entire geometric surface as determined by CT-scans. This study highlights the role of geometric surface area in normalizing current generation and the need to use more surface roughness parameters to correlate anode properties, bacterial adhesion, and current generation.

High‐performance Photoelectrochemical Hydrogen Production Using Asymmetric Quantum Dots

AbstractSolar‐driven photoelectrochemical (PEC) reactions using colloidal quantum dots (QDs) as photoabsorbers have shown great potential for the production of clean fuels. However, the low H2 evolution rate, consistent with low values of photocurrent density, and their limited operational stability are still the main obstacles. To address these challenges, the heterostructure engineering of asymmetric capsule‐shaped CdSe/CdxZn1‐xSe QDs with broad absorption and efficient charge extraction compared to pure‐shell QDs is reported. By engineering the shell composition from pure ZnSe shells into CdxZn1‐xSe gradient shells, the electron transfer rate increased from 4.0 × 107 s−1 to 32.7 × 107 s−1. Moreover, the capsule‐shaped architecture enables more efficient spatial carrier separation, yielding a saturated current density of average of 25.4 mA cm−2 under AM 1.5 G one sun illumination. This value is the highest ever observed for QDs‐based devices and comparable to the best‐known Si‐based devices, perovskite‐based devices, and metal oxide‐based devices. Furthermore, PEC devices based on heterostructured QDs maintained 96% of the initial current density after 2 h and 82% after 10 h under continuous illumination, respectively. The results represent a breakthrough in hydrogen production using heterostructured asymmetric QDs.