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# Huazhong University of Science and Technology and Donghua University teams unlock d–p orbital coupling for a high-performance hydrazine hydrate fuel cell
- URL: https://research-pop.com/huazhong-university-of-science-and-technology-and-donghua-university-teams-unlock-d-p-orbital-coupling-for-a-high-performance-hydrazine-hydrate-fuel-cell/
- Published: 2026-09-21T13:40:10.000Z
- Updated: 2026-09-21T13:40:10.000Z
- Author: ResearchPOP
- Tags: Materials Science, Chemistry

![](https://storage.ghost.io/c/7c/5e/7c5e0911-739b-4a35-94eb-3e810bf78ba7/content/images/2026/09/Screenshot-2026-09-21-at-15.09.21.png)

**Source**: [https://doi.org/10.1002/adma.75109](https://doi.org/10.1002/adma.75109?ref=research-pop.com)

## At a glance

A multi-institutional team led by researchers at Huazhong University of Science and Technology and Donghua University has developed a linker-defect strategy for tuning the interface between Pt nanoparticles and a nickel–ferrocene metal–organic framework. Partial replacement of the ditopic Fc linker with a monotopic Fc′ modulator creates a graded series of ligand defects and undercoordinated Ni–O environments in Pt@NiFc₁₋ₓFc′ₓ-MOF.

The intermediate composition, Pt@NiFc₀.₉₅Fc′₀.₀₅-MOF, gives the strongest overall performance in the reported series. It reaches 1000 mA cm⁻² for hydrogen evolution at an overpotential of 180 mV and 2000 mA cm⁻² for hydrazine oxidation at a working potential of 346 mV. In hydrazine-assisted hydrogen production, the catalyst operates for 200 h at 500 mA cm⁻². A direct hydrazine hydrate–hydrogen peroxide fuel cell using the optimized anode reaches a peak power density of 441.22 mW cm⁻² at 80 °C.

The authors connect these results with an oxygen-mediated Pt–O–Ni interface. Controlled linker defects alter Pt anchoring, strengthen the built-in electric field and improve the matching of Pt 5d, O 2p and Ni 3d states. The study shows that the best-performing material does not contain the highest defect concentration. Instead, an intermediate defect level provides the most favourable balance among local coordination, interfacial charge transfer and catalytic-site stability.

## Background

Hydrazine is a carbon-free liquid fuel with a high volumetric energy density. The paper cites values of about 5.40 kWh L⁻¹ for anhydrous hydrazine and 3.24 kWh L⁻¹ for 64 wt% hydrazine hydrate. Its intended four-electron oxidation converts N₂H₄ into N₂ and water without directly producing carbon-containing products.

The reaction still requires several coordinated steps. N–H bonds must be cleaved sequentially, electrons must be transferred, intermediates must move and react at the surface, and the final products must desorb. Pt can support a selective four-electron hydrazine-oxidation pathway, but its cost makes efficient use of each Pt site important.

Interfaces between Pt and a second material offer a way to change how the metal binds reactants and transfers charge. When two materials with different work functions come into contact, electrons redistribute until their Fermi levels approach equilibrium. This redistribution can create band bending, a space-charge region and a built-in electric field. The resulting interfacial polarization can direct charge and change the electronic state of nearby catalytic sites.

Metal–organic frameworks provide a chemically adjustable platform for constructing such interfaces. Their linkers and metal nodes can be modified to control local defects, coordination and the anchoring environment of supported nanoparticles. In this study, the researchers use a nickel–ferrocene framework and vary the fraction of a monotopic Fc′ modulator to tune the Pt–MOF junction systematically.

## Research question

How do linker-directed defects influence Pt nanoparticle anchoring, Pt 5d–O 2p–Ni 3d orbital coupling and charge transfer across an oxygen-mediated Pt–O–Ni interface?

The researchers then examine whether these changes improve hydrogen evolution, hydrazine oxidation, hydrazine-assisted hydrogen production and complete fuel-cell performance while reducing Pt use. By comparing defect-free, low-defect, intermediate-defect and high-defect materials, the study also tests whether controlled defect concentration is more important than simply introducing as many defects as possible.

## Inside the study

The catalyst series is prepared by partially replacing the ditopic Fc linker with the monotopic Fc′ modulator, followed by hydrothermal synthesis and mild etching. The substitution creates missing-linker environments and undercoordinated Ni–O sites that can anchor Pt nanoparticles and reshape the electronic structure of the interface.

X-ray diffraction and microscopy show that the framework features and nanosheet morphology are retained across the series. The Pt particles remain predominantly small and crystalline, with mean sizes ranging from 2.78 to 3.25 nm and a reported Pt(111) lattice spacing of 0.23 nm. Atomic-resolution imaging supports the description of Pt nanoparticles attached to the MOF rather than isolated Pt atoms.

Calculations first compare how the defect level affects formation of the Pt–MOF interface. The intermediate-defect model, Pt@NiFc-MOF-defect2, has the lowest reported formation energy at −6.552 eV. It also gives a relative Pt–O–Ni orbital-energy-alignment index of 93.70% and the highest normalized pathway index of 1.00 in the model comparison. These results point to an intermediate structure in which Pt anchoring and the oxygen-mediated electronic pathway are simultaneously favoured.

The calculations identify interfacial Pt as the preferred centre for hydrazine adsorption and activation. In the intermediate-defect model, the N₂H₄ adsorption energy is −2.67 eV on Pt and −1.74 eV on Ni. The corresponding Pt value in the defect-free model is −2.58 eV. Charge-density and crystal-orbital-Hamilton-population analyses connect the modified interface with stronger N–H activation.

Along the calculated hydrazine-oxidation pathway, desorption of \*N₂ is the largest uphill step. Its free-energy requirement decreases from 0.81 eV on the defect-free interface to 0.75 eV on the intermediate-defect structure. The authors use this comparison to show how the altered Pt–O–Ni environment affects both initial hydrazine binding and the later release of nitrogen.

Ni K-edge and Pt L₃-edge X-ray absorption measurements provide complementary views of the local interface. The fitted structures include Ni–O–Pt and Pt–O or Pt–O–Ni paths together with Pt–Pt contributions. The apparent Pt–O distance shortens from 3.89 to 3.66 Å after defect engineering. Simulated structures and charge-density maps show electron accumulation near Pt and depletion around adjacent Ni–O units, supporting charge transfer through the oxygen-containing interface.

Electronic measurements then follow how the junction responds to defect concentration. Mott–Schottky measurements indicate n-type behaviour. Photoluminescence reaches its lowest intensity at the intermediate defect level rather than in the material with the greatest defect concentration, again showing that the electronic response passes through an optimum.

The measured work function is 3.63 eV for NiFc-MOF and 3.31 eV for NiFc₀.₉₅Fc′₀.₀₅-MOF. The corresponding values estimated for the supported Pt nanoparticles are 6.09 and 6.03 eV. This mismatch favours electron transfer from the framework towards Pt when the interface forms.

The zeta-potential change rises from 5.20 mV for Pt@NiFc-MOF to 9.58 mV for the optimized interface. Combining Kelvin-probe-force-microscopy surface potentials with charge densities derived from the zeta-potential measurements, the authors calculate a relative apparent built-in-field index about 1.50 times that of the defect-free Pt@NiFc-MOF interface. Together, these measurements support stronger interfacial polarization at the intermediate defect concentration.

The electrochemical tests connect this interface tuning with catalytic performance. In 1.0 M KOH, Pt@NiFc₀.₉₅Fc′₀.₀₅-MOF requires an overpotential of 180 mV to reach 1000 mA cm⁻² for the hydrogen-evolution reaction. Pt@NiFc-MOF requires 254 mV under the same comparison, while Pt/C requires 466 mV.

Hydrazine oxidation is measured in 0.5 M N₂H₄ and 1.0 M KOH. The optimized catalyst reaches 2000 mA cm⁻² at a working potential of 346 mV. Pre-adsorbed CO strongly suppresses the activity, supporting Pt as the main site for hydrazine adsorption and oxidation while the surrounding MOF interface regulates its electronic environment.

Working-state spectroscopy shows that the Pt–O–Ni interface continues to respond as the applied potential changes. The Ni absorption edge shifts slightly towards lower energy and the Ni–O amplitude decreases. At the same time, the Pt white-line intensity and Pt–O contribution increase, while the Pt–Pt contribution decreases. The authors interpret these linked changes as adaptive charge redistribution and oxygen-coordination reconstruction across the Pt–O–Ni interface.

In situ infrared spectroscopy follows adsorbed N₂H₄ and N₂Hₓ intermediates during reaction. Online mass spectrometry detects a clear N₂ signal while the NH₃-related signal remains near baseline under the tested conditions. These observations support the proposed four-electron oxidation route towards nitrogen rather than an ammonia-forming pathway.

The researchers next combine hydrazine oxidation at the anode with hydrogen evolution at the cathode. In this assisted hydrogen-production configuration, the catalyst operates for 200 h at 500 mA cm⁻². Watt–Crisp colorimetry detects 3 ppb residual hydrazine after 80 min and approximately 99% removal in each of three cycles. The collected H₂ and N₂ volumes are close to a 2:1 ratio, consistent with the overall splitting of hydrazine into hydrogen and nitrogen.

At 0.2 V versus RHE, the authors report a 9.55-fold higher hydrazine-oxidation current per unit electrode cost than Pt/C. This comparison combines the reaction current with the direct material cost of the tested electrodes and reflects the lower Pt requirement of the MOF-supported catalyst.

The final device pairs hydrazine hydrate with hydrogen peroxide in an all-liquid fuel cell. This design avoids the gas–liquid oxygen-transport step required in a hydrazine–oxygen cell. With the optimized anode, the open-circuit voltage reaches 1.703 V, compared with 1.589 V for Pt/C.

The peak power density is 261.35 mW cm⁻² at 20 °C and 441.22 mW cm⁻² at 80 °C. The Pt/C comparison reaches 239.43 mW cm⁻² at 80 °C. During discharge at 200 mA cm⁻² and 20 °C, renewal of the electrolyte after the first 100 h restores the open-circuit voltage to about 1.65 V. The peak power density retains about 84% of its initial value.

The reported apparent fuel-to-electricity conversion efficiency is 53.14%, while the energy efficiency is 47.85%. Relative to Pt/C, the optimized anode uses 76.4% less Pt and delivers 7.81 times greater Pt-mass-specific peak power. Its peak-power output per unit direct anode cost is 16.3% higher.

Across these measurements, the intermediate defect concentration repeatedly stands out. It provides the most favourable Pt anchoring in the calculations, the lowest photoluminescence response, stronger apparent interfacial polarization and the highest electrochemical and device performance in the series. Increasing the defect level beyond this point does not continue to improve the catalyst.

## Takeaways and outlook

The study shows how controlled linker defects can tune a Pt nanoparticle–MOF interface across several connected scales. At the atomic level, the defects alter local Ni–O coordination and Pt anchoring. Electronically, they improve the alignment of Pt 5d, O 2p and Ni 3d states and strengthen interfacial charge redistribution. During operation, the oxygen-mediated interface adapts through coupled changes in Pt and Ni coordination.

The optimized Pt@NiFc₀.₉₅Fc′₀.₀₅-MOF supports ampere-level hydrogen evolution and hydrazine oxidation, operates for 200 h in hydrazine-assisted hydrogen production and reaches 441.22 mW cm⁻² in the hydrazine hydrate–hydrogen peroxide fuel cell at 80 °C. Its reduced Pt loading also increases Pt-mass-specific power and improves the reported cost-normalized output.

The central design message is that defect concentration needs to be balanced. In this catalyst family, the intermediate linker-defect level creates the most effective Pt–O–Ni pathway and built-in electric field. The work links molecular-level framework design with interfacial orbital coupling, reaction performance and complete fuel-cell operation.

## About the researchers

Xia Zhang, Yuxiao Liu, Linfeng Li, Yaping Huang and Yuanjie Pang are affiliated with Huazhong University of Science and Technology. Jianping Yang is affiliated with Donghua University. Chundong Wang is affiliated with Huazhong University of Science and Technology, Prince Sultan University and Chemnitz University of Technology. Mengni Liu is affiliated with Fudan University. Muhammad Humayun is affiliated with Prince Sultan University. Junfeng Huang and Cailing Xu are affiliated with Lanzhou University. Xuefei Xu is affiliated with Hainan University. Hussein A. Younus is affiliated with Sultan Qaboos University, and Anton Nikiforov is affiliated with the University of Antwerp.

Xia Zhang is the first author. Jianping Yang and Chundong Wang are the corresponding authors.

## Original research

Xia Zhang; Mengni Liu; Yuxiao Liu; Linfeng Li; Muhammad Humayun; Junfeng Huang; Yaping Huang; Xuefei Xu; Hussein A. Younus; Anton Nikiforov; Yuanjie Pang; Cailing Xu; Jianping Yang; Chundong Wang. “Unlocking d–p Orbital Coupling via Built-in Electric Fields for High-Performance Hydrazine Hydrate Fuel Cell.” *Advanced Materials*, 2026, e75109\. Published online 20 September 2026\. DOI: [10.1002/adma.75109](https://doi.org/10.1002/adma.75109?ref=research-pop.com).

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