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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Novel waste-derived non-noble metal catalysts to accelerate acidic and alkaline hydrogen evolution reaction

Carbon substrate support is a promising approach to facilitate catalytic activity of non-noble metal catalysts in hydrogen evolution reactions (HER). Here, in this paper, we report a waste-derived electrocatalyst P-CoNiO 2 @NC synthesized under mild condition. It exhibits outstanding HER performance in both acid (η 10 = 64.6 mV) and alkaline (η 10 = 96.4 mV) condition with good stability. Especially, it begins to outperform commercial Pt/C when the current density is over 74 mA/cm 2 in acid electrolyte and 29 mA/cm 2 in alkaline electrolyte. Moreover, the waste-derived carbon substrate could effectively promote HER activity of other dual 3d TMOs such as Fe and Co, Fe and Ni. The improved HER activity originates from electron transfer, electronic structure adjustment and optimization of intermediates adsorption according to X -ray photoelectron spectroscopy and density functional theory calculations. This work provides a new insight for converting wastes into value-added products and a sustainable and friendly strategy to facilitate hydrogen energy production.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Mathematical Modeling of Hydroxide-Exchange-Membrane Water Electrolyzer

Water electrolyzers can transform intermittent renewable energy like solar energy and wind energy into the chemical energy of hydrogen with zero greenhouse-gas emissions. The hydroxide-exchange membrane electrolyzer (HEME) combines the capability to produce pressurized hydrogen with the advantage of being able to use low or non-platinum group metal (PGM) electrocatalysts in the alkaline environment.1 Hydroxide salts, for example, KOH, are added to the HEME water feed on both anode and cathode to improve its performance. However, the specific mechanism of performance improvement still needs to be further understood. In addition, at high current densities, bubble evolution can result in mass-transport limitations, a less well studied phenomena. Mathematical modeling is ideal to explore these issues as it is cost and time efficient and can deconvolute the physics, processes, and observed phenomena and study the applied-voltage breakdown. In this work, we extend our previously developed 1D two-phase continuum model2 to study the varies processes in the HEME and provide insights on performance optimizations. First, the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) kinetics at different hydroxide concentrations have been studied by rotating disk electrodes (RDE) and implemented in the model. Then, the model is calibrated and validated against experimental HEME polarization curves for different KOH concentrations as a liquid electrolyte. The model clearly shows a performance increase with increasing KOH concentrations, which is consistent with the experimental results. The reduced ohmic resistance and increased electrochemical active surface area (ECSA) are the two main reasons for performance increase. The large amount of hydroxide in the liquid electrolyte not only helps to distribute the reactant hydroxide throughout the catalyst layer (CL), which reduces ohmic loss, but also enables reaction at the interface between the liquid electrolyte and electrocatalyst, which increases the ECSA. Applied-voltage breakdown demonstrates that the electrolyzer performance is dominated by anode kinetics and ohmic loss. A comparison with the DI water feed shows a more uniform current distribution in the anode CL when KOH is added, which indicates a higher utilization of the CL. Second, we present modeling on the effects of bubble coverage. As gas evolves, part of the ECSA is minimized due to bubble coverage. To account for this effect, an empirical relationship between the fractional bubble coverage and the current density is implemented in the model.3 The model shows this bubble coverage effect is more pronounced at large current densities with DI water feed. Acknowledgements This work was funded under the HydroGEN Consortium by the Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office, of the U. S. Department of Energy under contract number DE-AC02-05CH11231. References R. Abbasi, B. P. Setzler, S. Lin, J. Wang, Y. Zhao, H. Xu, B. Pivovar, B. Tian, X. Chen, G. Wu and Y. Yan, 31, 1805876 (2019). L. N. Stanislaw, M. R. Gerhardt and A. Z. Weber, ECS Transactions, 92, 767 (2019). H. Vogt and R. J. Balzer, Electrochimica Acta, 50, 2073 (2005).

Liu, Jiangjin↗
NASA NTRS1985

Hydrogen and water desorption on the moon - Approximate, on-line simulations

The basic models that have been used over the last 15 years to describe the accumulation and release of solar wind-related species at lunar conditions at the lunar surface are reviewed. Recent results which show that these models are not totally valid are discussed. It is suggested that mature lunar surface soils may act as efficient converters for transforming the flux of energetic solar wind protons into a flux of low-energy hydrogen and water molecules continuously injected into the lunar atmosphere.

Blanford, G. E.↗
DOE OSTI2020

Deposition of an ultrathin palladium (Pd) coating on SAPO-34 membranes for enhanced H 2 /N 2 separation

Hydrogen energy has attracted great attention due to its properties of high energy transferring efficiency and zero pollution emission. Zeolite membranes are promising candidates for H 2 separation because of their uniform, molecular-sized pores and high thermal and mechanical stabilities. However, thicker membranes or modification treatments are often necessary to eliminate the defects formed during synthesis and post calcination, leading to low gas permeance. In this paper, we reported the deposition of an ultrathin palladium (Pd) coating on SAPO-34 membranes to improve H 2 separation performance. H 2 /N 2 selectivity was greatly increased by deposition of an ultrathin Pd coating on SAPO-34 membranes, while maintaining similar H 2 permeance. This might be attributed to the dissociative adsorption and associative desorption of H 2 on Pd, as well as fast diffusion of H 2 through ultrathin Pd coating. We also noticed that excessive Pd deposition would lead to the formation of cracks on SAPO-34 membranes, leading to deteriorated membrane performance.

08 HYDROGEN↗
DOE OSTI2024

Methane Pyrolysis for CO2-free H2 and Carbon Nanomaterials - CRADA 576 (Final Report)

In this CRADA project we continued to develop the Pacific Northwest National Laboratory (PNNL) patent-pending Regenerable Catalytic Pyrolysis (ReCaP) process technology for producing CO 2 -free hydrogen (H 2 ) from inexpensive and domestically-abundant natural gas (NG), while simultaneously reducing H 2 ’s net production cost to $\$$1.0/kg through the sale of valuable crystalline solid carbon co-product. Producing clean hydrogen at this price is a DOE Hydrogen Energy Earthshot goal. This effort builds on our prior catalyst and processing advances made thermocatalytic decomposition of methane (TCD). The additional scope performed here accelerated the commercial deployment of TCD for CO 2 -free H 2 and valuable solid carbon nanotubes (CNT) co-product, by i) scaling up the production of CNT co-product using a fluidized bed reactor (25 g catalyst scale versus the 1 g catalyst scale demonstrated prior), ii) producing approximately 1 kg of CNT byproduct, produced via multiple cycles of TCD, carbon-catalyst separation, and catalyst re-synthesis, to enable the production of sufficient quantities of solid carbon so as to explore its market potential, iii) understanding the quality of the co-product CNTs, produced at larger scale, using advanced characterization, and iv) beginning to explore multiple promising high volume carbon product applications (e.g., aluminum and polymer composites, steel additive, and cement reinforcement applications). We are in discussions with Department of Energy and potential commercial partners to continue funding of this effort with the goal to facilitate eventual commercial deployment.

08 HYDROGEN↗
NASA NTRS1975

A preliminary systems-engineering study of an advanced nuclear-electrolytic hydrogen-production facility

An advanced nuclear-electrolytic hydrogen-production facility concept was synthesized at a conceptual level with the objective of minimizing estimated hydrogen-production costs. The concept is a closely-integrated, fully-dedicated (only hydrogen energy is produced) system whose components and subsystems are predicted on ''1985 technology.'' The principal components are: (1) a high-temperature gas-cooled reactor (HTGR) operating a helium-Brayton/ammonia-Rankine binary cycle with a helium reactor-core exit temperature of 980 C, (2) acyclic d-c generators, (3) high-pressure, high-current-density electrolyzers based on solid-polymer electrolyte technology. Based on an assumed 3,000 MWt HTGR the facility is capable of producing 8.7 million std cu m/day of hydrogen at pipeline conditions, 6,900 kPa. Coproduct oxygen is also available at pipeline conditions at one-half this volume. It has further been shown that the incorporation of advanced technology provides an overall efficiency of about 43 percent, as compared with 25 percent for a contemporary nuclear-electric plant powering close-coupled contemporary industrial electrolyzers.

Escher, W. J. D.↗
DOE OSTI2021

Numerical Simulations of Cryogenic Hydrogen Cooling in Vortex Tubes with Smooth Transitions

Improving efficiency of hydrogen cooling in cryogenic conditions is important for the wider applications of hydrogen energy systems. The approach investigated in this study is based on a Ranque-Hilsch vortex tube (RHVT) that generates temperature separation in a working fluid. The simplicity of RHVT is also a valuable characteristic for cryogenic systems. In the present work, novel shapes of RHVT are computationally investigated with the goal to raise efficiency of the cooling process. Specifically, a smooth transition is arranged between a vortex chamber, where compressed gas is injected, and the main tube with two exit ports at the tube ends. Flow simulations have been carried out using STAR-CCM+ software with the real-gas Redlich-Kwong model for hydrogen at temperatures near 70 K. It is determined that a vortex tube with a smooth transition of moderate size manifests about 7% improvement of the cooling efficiency when compared vortex tubes that use traditional vortex chambers with stepped transitions and a no-chamber setup with direct gas injection.

08 HYDROGEN↗
DOE OSTI2022

Understanding Subsidies to Achieve Diesel Powertrain Financial Parity for Heavy-Duty Fuel Cell Electric Vehicles

The development of a long-term sustainable hydrogen energy economy for commercial vehicle transportation will need to overcome key critical technical and logistics considerations in the near term. As compared to zero-emission powertrains, fossil-fuel-based powertrains provide mission flexibility and high uptime at a comparatively low total cost of ownership (TCO). While the incumbent carbon-intensive powertrains suffer from poor efficiency and are not sustainable to support global climate change initiatives in transportation decarbonization, techno-economic challenges continue to create complex barriers to the large-scale displacement of these with highly electrified powertrains architectures. Here, this article specifically addresses opportunities that well-targeted subsidies would afford in achieving fuel cell electric powertrain financial parity with diesel powertrains in heavy-duty trucks (HDTs). It shows that a rigorous assessment of system TCO factors will be critical in designing a viable subsidy strategy. Based on powertrain component and fuel price points, subsidy variations (for both capital expenses and operating fuel expenses) are assessed and quantified to determine where and how much subsidies should be leveraged to accelerate achieving diesel system financial parity. It shows that subsidies on hydrogen fuel expenses (and associated constituents) will play an important role in achieving this goal while subsidies on capital expenses (the more typical subsidy formulation) may not always be the preferred subsidy strategy. The results provide subsidy agencies with clear guidance and a database approach to characterize and implement viable HDT hydrogen powertrain system subsidy strategies. The approach may be readily tailored for other applications and system architectures.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2025

Nickel Sulfide-Nanowire-Filled Carbon Nanotubes as an Efficient Overall Water Splitting Electrocatalyst

Pursuing stable, efficient, and cost-effective nanostructured bifunctional electrocatalysts is crucial for advancing the electrochemical water splitting process and enabling clean hydrogen energy production. In recent years, considerable efforts have focused on developing highly efficient and durable commercial electrocatalysts for the oxygen evolution reaction (OER) and overall water splitting (OWS). This research introduces an OWS electrocatalyst-nickel sulfide-filled carbon nanotubes grown on a carbon cloth substrate (Ni 3 S 2 @CNTs/CC), synthesized via a one-step in-situ process. The synergistic integration of metal sulfide (Ni 3 S 2 ) and carbon nanotubes provides abundant active sites for catalytic reactions, ensuring a robust composite nanostructure with enhanced durability. Furthermore, the electrocatalytic performance for OER and OWS has been significantly improved by a simple acid treatment to the electrocatalysts, which introduces physical and chemical defects, particularly oxygen functional groups (the acid-treated sample is termed as Ni 3 S 2 @CNTs/CC-AT). As OER electrocatalysts, Ni 3 S 2 @CNTs/CC and Ni 3 S 2 @CNTs/CC-AT present overpotentials of 304 and 200 mV, respectively, for achieving a current density of 10 mA/cm 2 in the OER process. Furthermore, for complete water splitting in 1.0 M KOH electrolyte, Ni 3 S 2 @CNTs/CC and Ni 3 S 2 @CNTs/CC-AT exhibit potentials of 1.63 and 1.44 V, respectively, to achieve a current density of 10 mA/cm 2 when employed as both anode and cathode. Moreover, Ni 3 S 2 @CNTs/CC and Ni 3 S 2 @CNTs/CC-AT demonstrate durable nature for 22 and 20 h durability in the OER and OWS processes, respectively, offering a promising alternative to ruthenium- and iridium-based electrocatalysts for electrochemical hydrogen production through water splitting. In conclusion, the in-situ synthesis method and acid treatment strategy described in this research are promising approaches to fabricating high-performance encapsulated carbon-nanotube-based electrocatalysts.

36 MATERIALS SCIENCE↗
DOE OSTI2024

GEOS: A performance portable multi-physics simulation framework for subsurface applications

GEOS is a simulation framework focused on solving tightly coupled multi-physics problems with an initial emphasis on subsurface reservoir applications. Currently, GEOS supports capabilities for studying carbon sequestration, geothermal energy, hydrogen storage, and related subsurface applications. The unique aspect of GEOS that differentiates it from existing reservoir simulators is the ability to simulate tightly coupled compositional flow, poromechanics, fault slip, fracture propagation, and thermal effects, etc. Extensive documentation is available on the GEOS documentation pages (GEOS Documentation, 2024). Note that GEOS, as presented here, is a complete rewrite of the previous incarnation of the GEOS referred to in (Settgast et al., 2017).

58 GEOSCIENCES↗
DOE OSTI2020

Synthesis of Synergistic Nitrogen-Doped NiMoO 4 /Ni 3 N Heterostructure for Implementation of an Efficient Alkaline Electrocatalytic Hydrogen Evolution Reaction

Electrochemical water splitting is considered as an effective and promising method to produce the ideal hydrogen energy to solve the energy crisis and environmental pollution problems. In this paper, we successfully synthesized the N-doped NiMoO 4 /Ni 3 N heterostructure, which exhibited an efficient HER performance with a lower overpotential of 51 mV at 10 mA cm -2 and a lower Tafel slope value of 45.47 mV dec -1 compared with those of NiMoO 4 , N-doped NiMoO 4 , or Ni 3 N owing to the synergistic effect of N doping and construction of the superior heterostructure. When the N-doped NiMoO 4 /Ni 3 N heterostructure is used as a cathode and the well-recognized excellent OER material (NiFe-LDH) is used as an anode to construct the two-electrode electrolyzer, the system requires only 1.506 and 1.559 V to achieve the current densities of 10 and 20 mA cm -2 , respectively, which are lower than those of the commercial Pt/C//RuO 2 system (1.573 and 1.634 V, respectively) or many other reported systems. At the same time, this two-electrode system demonstrates excellent durability in electrocatalytic water splitting. This design method paved the way for the development of another electrocatalytic system.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Intermediate Temperature Proton‐Conducting Solid Oxide Electrolysis Cells with Improved Performance and Durability

Technical understanding: A high-performance and stable intermediate temperature proton-conducting solid oxide electrolysis cell (PCEC) will add significantly to the hydrogen roadmap of EERE. However, the low electrocatalytic activity of the air electrode and the instability of the electrolyte are technical barriers. In this research, we utilized computational fluid dynamic modeling and materials/microstructure engineering to investigate the complex reaction chain and to improve the performance and reliability of the protonic ceramic electrochemical cells. An active and stable Pr 1.8 Ba 0.2 NiO 4+δ -BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) scaffold conformal coating electrode was rationally designed where the robust Pr 1.8 Ba 0.2 NiO 4+δ functions both as a catalytic active and a protective layer. The PCECs with porosity-optimized scaffold conformal coating electrodes demonstrate 1.46 Acm -2 under 1.3 V at 600°C, which is among the highest in recent years. The final optimization by computational fluid dynamic modeling and conformal coating technique was applied to evolve the PCEC air electrode from Pr 2 NiO 4+δ to Pr 1.8 Ba 0.2 NiO 4+δ -BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ scaffold conformal coating. The electrolysis current was boosted from 0.445A/cm 2 to 1.46A/cm 2 at 600°C and 1.3V. A superior low degradation rate of 1mV/kh was achieved in a 5000-hour of operation. Technical effectiveness and economic feasibility: The effectiveness of this TCO conformal coating on electrolyte backbone as air electrode has been proven by long-term demonstration. Based on the highly conductive BZCYYb electrolyte and the TCO steam electrode PNO, this project rationally took advantage of the existent materials to structure a PCEC device with high TRL and low risk. The solution infiltration method used to structure the conformal coating is a standard method used by the solid oxide cell community. Very minimal adoption is needed in the current SOC fabrication process. It is a cost-effective, scalable method for manufacturing, and brings up remarkable impact on the current technical status of PCEC. Benefit to the public: The findings in the research showed the industry that the severe challenge in PCEC can be overcome in a practical way. A various energy-hydrogen ecosystem is not beyond reach. The success of this technology provides sustainable and affordable H 2 to society. It will stimulate investment from the governmental and private sectors in response to the device manufacture and deployment, and the related infrastructure construction. It will generate high-pay domestic jobs and environmental benefits to the general public in the United States.

08 HYDROGEN↗
DOE OSTI2022

PGM-Free Oxygen-Reduction Catalyst Development for Proton-Exchange Membrane Fuel Cells: Challenges, Solutions, and Promises

Proton-exchange membrane fuel cells (PEMFCs) are efficient and clean hydrogen energy technologies for transportation and stationary applications. Highly active and durable low-cost cathode catalysts for the oxygen-reduction reaction (ORR) under challenging acidic environments are desperately needed to address the cost and durability issues of PEMFCs. The most promising platinum group metal (PGM)-free catalysts for the ORR in acidic media are atomically dispersed and nitrogen-coordinated metal site catalysts denoted as M–N–C, M = Fe, Co, or Mn. Due to significant efforts in the past few decades, these catalysts have demonstrated much-improved ORR activity and promising initial fuel cell performance approaching traditional Pt/C catalysts. However, the insufficient long-term stability (up to 5000 h) under PEMFC operation represents a primary technical barrier to making current PGM-free catalysts less viable yet in PEMFCs. In this Account, we highlight recent advances in synthesizing efficient PGM-free catalysts for the ORR in PEMFCs, emphasizing effective strategies to improve mass and intrinsic activity and the possible degradation mechanisms. In particular, a chemical doping method based on the zeolitic imidazolate framework (ZIF)-8 represents the key to developing efficient M–N–C catalysts containing atomically dispersed and nitrogen-coordinated single metal active sites (i.e., MN 4 ). The newly acquired understanding of the formation mechanism of MN 4 active sites during the thermal activation and its correlation to catalytic properties guide the rational catalyst design rather than relying on current trial-and-error approaches. Considerable efforts have further been invested in increasing the active site density and enhancing intrinsic activity by regulating carbon-phase structures and the local coordination environment. Furthermore, these highly active catalysts usually suffer from significant activity loss during the ORR. Therefore, breaking the activity–stability trade-off is the key to simultaneously achieving activity and stability in one catalyst, which is discussed on the basis of our recent successes in regulating local carbon structures surrounding active single metal sites. Significant research efforts toward understanding the degradation mechanisms and improving the lifetime of PGM-free catalysts are still crucial for viable applications in the future. Novel electrode designing strategies are needed to translate the PGM-free catalysts’ ORR activity to solid-state electrolyte-based membrane electrode assemblies (MEAs) with robust three-phase (i.e., gas–liquid–solid) interfaces for efficient charge and mass transports for performance improvement. On the basis of our effort at the University at Buffalo supported by ElectroCat Consortium associated with U.S. DOE’s Hydrogen and Fuel Cell Technologies Office, we provide a perspective on PGM-free cathode catalysts concerning remaining bottlenecks and future opportunities, aiming to inspire the community in both mechanistic understanding and technological development.

08 HYDROGEN↗
DOE OSTI2022

Methane Pyrolysis for CO2-free H2 and Carbon Nanomaterials (Abstract)

We propose to continue to develop a new process for producing CO2-free hydrogen (H2) from inexpensive and domestically-abundant natural gas (NG), while simultaneously reducing H2’s net production cost to $1.0/kg through the sale of valuable crystalline solid carbon co-product. Producing clean hydrogen at this price is a DOE Hydrogen Energy Earthshot goal. Cost effective production of clean H2 is also of commercial relevance to project partners Southern California Gas Company (SoCalGas) and startup company C4-MCP, who aim to further develop, demonstrate at scale, and ultimately deploy the new process technology developed on this project in order to meet regulatory demands in the State of California. In the current project we have focused on i) understanding the catalyst science for thermocatalytic decomposition of methane (TCD), which resulted in the development of a patent pending bimetallic catalyst offering favorable activity, stability, and selectivity under industrially relevant process conditions, ii) developing a novel, patent pending process to enable the separation of produced carbon and catalyst, and re-synthesis of the catalyst using recycled materials, iii) performing limited characterization of the produced carbon materials, and iv) performing detailed process modeling in order to perform techno economic assessment. The additional scope proposed here will accelerate the commercial deployment of TCD for CO2-free H2 and valuable solid carbon nanotubes (CNT) co-product, by i) scaling up the production of CNT co-product using a scalable, fluidized bed reactor (25 g catalyst scale versus the 1 g catalyst scale demonstrated to-date), ii) producing at least 40 g of CNT product, produced via multiple cycles of TCD, carbon-catalyst separation, and catalyst re-synthesis, to enable the production of sufficient quantities of solid carbon so as to explore its market potential, iii) understanding the quality of the co-product CNTs, produced at larger scale, through advanced characterization, and iv) beginning to explore multiple promising high volume carbon product applications (thermoplastics, automotive composites, battery, and cement reinforcement applications).

08 HYDROGEN↗
DOE OSTI2023

Effects of Anionic Polymer Modification of Dye‐Sensitized Niobate Photocatalysts on Solar‐Driven Z‐Scheme Overall Water Splitting

Pt‐intercalated calcium niobate nanosheets (Pt/HCa 2 Nb 3 O 10 ) sensitized by a Ru(II) complex dye are good photocatalysts for producing H 2 from aqueous solutions containing I − as a reversible electron donor. These materials are applicable to Z‐scheme overall water splitting in combination with a WO 3 ‐based O 2 ‐evolving photocatalyst under simulated sunlight. In this work, the effects of anionic polymer modification of the dye‐sensitized nanosheets are examined by adsorbing sodium poly(styrenesulfonate) (PSS), sodium polyacrylate, sodium polymethacrylate (PMA), or sodium poly(4‐styrenesulfonic‐ co ‐maleic acid) onto the dye‐sensitized nanosheet surface. For half‐cell H 2 ‐evolution reaction in the presence of NaI, all of the polymers have a positive impact on the activity under visible light at lower light intensity, whereas only PMA is effective under high light‐intensity condition. For Z‐scheme overall water splitting with PtO x /H‐Cs‐WO 3 , PSS and PMA give almost the same solar‐to‐hydrogen energy conversion efficiencies (0.12% ± 0.01%) under optimized conditions. However, PMA operates better than PSS at relatively low and high NaI concentrations, which are in general disadvantageous for the H 2 ‐ and O 2 ‐evolving components of the Z‐scheme, respectively.

Energy & Fuels↗
DOE OSTI2023

Effects of Anionic Polymer Modification of Dye‐Sensitized Niobate Photocatalysts on Solar‐Driven Z‐Scheme Overall Water Splitting

In article number 2300629, Mallouk, Maeda and co-workers report that a surface modification of a dye-sensitized calcium niobate nanosheet photocatalyst with anionic polymers such as sodium polymethacrylate improves the activity for solar water splitting, giving a maximum solar-to-hydrogen energy conversion efficiency of 0.12±0.01% and an apparent quantum yield of 5.1% at 420 nm.

Yamamoto, Haruka↗
DOE OSTI2024

Stabilizing alkaline fuel cells with a niobium-doped brookite titanium dioxide catalyst support

Anion-exchange membrane fuel cells represent a promising and scalable approach for hydrogen energy utilization. However, their development is hindered by the weak bonding between metal catalysts and carbon supports, along with challenges in fabricating electronically/ionically conductive electrodes. Here, we report a composite cathode of Nb-doped brookite TiO 2 nanorods that have robust stability when combined with Pt nanoscale catalysts in an alkaline fuel cell. The composite cathode, fabricated without the addition of an ionomer, delivers a power density of 419 mW cm −2 at a current density of 650 mA cm −2 and a voltage retention of 81% at 100 mA cm −2 after 25 h, substantially outperforming a cathode fabricated from commercial Pt/C. Further investigations of the chemical structure, anion exchange capacity, and mass transfer resistance reveal that a solvent residue derived from N-methylpyrrolidone plays an important role in charge transfer and mass transport in the alkaline fuel cell.

alkaline fuel cell↗