"Exchanging sulfur for oxygen" strategy unlocks high-performance catalyst for green hydrogen production

A breakthrough strategy using sulfur-rich precursors to engineer porous heterojunctions has overcome critical bottlenecks in water-splitting catalysts, paving the way for green hydrogen production. Led by Professor Jian-Ping Lang of Soochow University, the research tackled the oxygen evolution reaction (OER) – a major hurdle in sustainable hydrogen generation that typically relies on scarce, expensive noble metals like iridium and ruthenium.

While transition metal molybdates offer a promising earth-abundant alternative, their potential has been limited by insufficient active sites and poor charge transfer. The Soochow University team's innovative solution, published in Nano Research (Tsinghua University Press), employed an "exchanging sulfur for oxygen" method to synthesize highly porous Fe₂(MoO₄)₃/CoMoO₄ heterojunction electrocatalysts with exceptional performance.

Key Innovation & Synthesis:

The catalyst was created by reacting ammonium tetrathiomolybdate [(NH₄)₂MoS₄] with iron and cobalt chlorides in solution, followed by controlled calcination. Crucially, during calcination, sulfur atoms oxidized into SO₂ gas, while HCl and NH₃ gases were simultaneously released. This synergistic gas evolution acted as a self-removing template, generating a wealth of interconnected macropores (>50 nm) and mesopores (2–50 nm). This led to a dramatically increased surface area of 87.44 m²·g⁻¹, 32 times larger than conventional catalysts, and the formation of a critical heterojunction interface enabling electron redistribution between Fe₂(MoO₄)₃ and CoMoO₄.

Record-Breaking Performance:

The engineered heterojunction catalyst delivered ultra-low overpotentials of just 244 mV to achieve a current density of 10 mA·cm⁻² in alkaline media, significantly outperforming commercial RuO₂ benchmarks and single-component molybdates. It also exhibited a small Tafel slope (47.4 mV·dec⁻¹) and exceptional stability over 100+ hours of continuous operation. Multi-current step testing confirmed its robustness even at high current densities.

Mechanism & Confirmation:
The porous architecture facilitated efficient mass and charge transport. Advanced characterizations (XPS, EXAFS) verified electron transfer from Co to Fe/Mo sites, optimizing the adsorption of reaction intermediates. Density Functional Theory (DFT) calculations confirmed that the heterointerface shifts the d-band center closer to the Fermi level, strengthening intermediate adsorption and reducing the energy barrier for the rate-determining step (*OOH formation).

Researcher Insights:

"Our sulfur-exchange strategy tackles two fundamental challenges simultaneously," explained corresponding author Professor Jian-Ping Lang. "It constructed vital hierarchical pores to expose buried active sites while optimizing charge transfer across atomic-level interfaces. This dual engineering would be key to achieving noble metal-like efficiency with earth-abundant elements."

"The gas evolution during the sulfur-to-oxygen conversion is pivotal," added co-corresponding author Associate Professor Fei-Long Li. "It spontaneously creates the intricate pore network essential for electrolyte penetration and establishes the electronic interactions at the heterojunction that drive the record performance."

Future Directions:
This team plans to extend this powerful strategy to other thiometallate precursors (e.g., tungsten, vanadium) to prepare advanced multi-metal oxycompound heterojunctions. They are also pursuing machine learning-guided optimization to further enhance the synergy between pore structure and heterointerface properties.

Collaborators & Funding:
Key contributors include Zhaochen Li (Soochow University) and Yongyong Cao (Jiaxing University). This research was supported by the National Natural Science Foundation of China (Grants U24A20507, 22271203, 22001021, 22478152), the State Key Laboratory of Organometallic Chemistry (Shanghai Institute of Organic Chemistry, Grant 2024KF005), the Open Research Fund of the State Key Laboratory of Coordination Chemistry (Nanjing University), the Collaborative Innovation Center of Suzhou Nano Science and Technology, and the Project of Scientific and Technologic Infrastructure of Suzhou (SZS201905).

About Nano Research

Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.