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New findings in the research of electrochemical hydrogen generation

New findings in the research of electrochemical hydrogen generation

Researchers at Nanjing Normal University have made important breakthroughs in the design and synthesis of multiple heterogeneous nanostructures and their dual-function in electrocatalytic hydrogen evolution reaction (HER) applications. They made the first demonstration of enhancing electrocatalytic HER behavior by constructing a rod-like Ni@Ni2P–Ru heterostructure using a simple one-pot synthetic method.

The paper entitled “Ru Modulation Effects in the Synthesis of Unique Rod-like Ni@Ni2P–RuHeterostructures and Their Remarkable Electrocatalytic Hydrogen Evolution Performance” was published in Journal of the American Chemical Society (IF 13.858) on February 7, 2018.

The findings were made by research groups led by Prof. Zhihui Dai and Prof. Jianchun Bao, professors of the School of Chemistry and Materials Science. Ying Liu, a PhD Candidate of the School of Chemistry and Materials Science is the lead author of this paper.

Hydrogen generated from water splitting is an ideal alternative for future energy supplies when compared to fossil fuels. To scale up the production of hydrogen, highly efficient electrocatalysts that improve the energy transfer efficiency in the HER are crucial. Although Pt is recognized as the state-of-the-art catalyst for the HER, the high cost largely impedes its commercial application.

To solve this problem, numerous efforts have been focused on earth-abundant non-Pt-based electrocatalysts. Among them, transition metal phosphides (TMPs) are one type of attractive catalysts for HER applications, even though their performance remains inferior to that of 20% Pt/C. An ideal HER electrocatalyst should possess an optimized ΔGH value of ∼0 eV. Meanwhile, good conductivity enables a catalyst with faster electron transport and improved electrocatalytic properties. Therefore, it is highly desirable to construct advanced TMPs with both moderate ΔGH values and great conductivity to obtain satisfactory catalytic activity.

As an effective catalyst for ammonia synthesis and benzene hydrogenation, Ru possesses a similar bond strength as Pt with hydrogen, but few have studied it as a viable alternative for electrocatalytic applications. This initiated the researchers’ desire of introducing Ru into Ni2P to improve the HER performance of phosphides.

By constructing the model of Ru–Ni2P hybrid structure and to evaluate its ΔGH via density functional theory calculations, researchers explored the construction of a distinctive Ru–Ni2P hybrid structure and demonstrated the first metal–phosphides–metal system consisting of Ru, Ni2P, and Ni, which forms unique multiheterogeneous Ni@Ni2P–Ru nanorods. Interestingly, a Ru modulation effect that promotes the desorption of H2 to achieve a moderate hydrogen adsorption energy (ΔGH), and enables the formation of Ni@Ni2Pnanorods via Ru–Ni coordination to enhance the conductivity was discovered. Due to its optimal ΔGH, improved conductivity and rod-like morphology, this catalyst shows superior electrocatalytic HER performances in both acidic and alkaline conditions, which are superior to those of some recently reported phosphides and close to that of commercial 20% Pt/C.

The synthetic strategy may also be applied to other similar TMPs or noble metals to grow novel heterostructures. The concept of metal–phosphides–metal nanostructures are expected to serve as a new type of robust catalyst for HER and other energy applications.

Support for the project was provided in part by the National Natural Science Foundation of China, the National Program on Key Basic Research Project and the PAPD of Jiangsu Higher Education Institutions.