Zhejiang University Team Publishes Latest AFM: Rare Earth-Induced Charge Polarization Drives Efficient Hydrogen Production in Medium-Entropy Alloys

Professor Xiao Xuezhang and Professor Chen Lixin's research team from Zhejiang University, in collaboration with related forces from Sun Yat-sen University, published their latest research findings titled "Rare-Earth-Induced Charge Polarization in Medium-Entropy Alloy Driving Fast Hydrogen Generation" in Advanced Functional Materials. The team proposed a "rare-earth-induced charge polarization" strategy to design high-performance medium-entropy alloy catalysts, achieving efficient hydrogen generation from the alcoholysis of ammonia borane (AB) at room temperature, providing new catalytic design ideas for the large-scale application of hydrogen energy. PhD students Chu Fei and Wang Jinze are the co-first authors of the paper.

The research background shows that the high-hydrogen-content compound ammonia borane (NH3BH3, AB) has a hydrogen storage density of 19.6 wt% and good environmental stability, making it an ideal material for hydrogen storage and production. Catalytic hydrogen production from AB and methanol can be carried out at room temperature without the generation of harmful ammonia, showing potential as a hydrogen source for fuel cell vehicles. Among these, dehydrogenation on the methanol side is the rate-determining step, requiring the development of highly active and stable catalysts to promote methanol decomposition. Current studies often use the d-band center to evaluate the adsorption capacity of catalysts, but due to the lack of clear distinction between the "adsorption-activation" two steps in methanol decomposition, the understanding of the catalytic mechanism is insufficient, limiting the design of high-performance catalysts.

To address this issue, the team proposed a "rare-earth-induced charge polarization" strategy, introducing rare earth element La with strong electron supply capability into the CuCoNi medium-entropy alloy (MEA) system, regulating the charge distribution between atoms, and achieving synergistic enhancement of "adsorption-activation." The study calculated the average atomic charge of the CuCoNiX-MEA system (X=V, Cr, and six other elements), screening La as the optimal doping component, which forms a significant charge difference with Cu/Co/Ni, laying the foundation for the synergy of "adsorption-activation."

The team synthesized single-phase CuCoNiLa-MEA catalysts using carbothermal reduction, and XRD, TEM, and other characterizations confirmed the successful solid solution of La atoms, determining 690°C as the optimal synthesis temperature. Performance tests showed that the TOF value of CuCoNiLa-MEA nanoparticles prepared at this temperature reached 102 molH2 molcat-1 min-1; when the doping ratio of La was 0.3, the catalyst performed best, with the TOF value increasing to 147.9 molH2 molcat-1 min-1, about 50% higher than that of CuCoNi-MEA. Kinetic studies revealed that its apparent activation energy was as low as 31.3 kJ mol-1, lower than the 35.6 kJ mol-1 of CuCoNi, significantly reducing the reaction kinetic barrier.

Mechanism studies revealed that after the introduction of La, significant interatomic charge polarization occurred: La exhibited a +1.124 e positive charge, while Cu/Co/Ni exhibited negative charges. Positively charged La adsorbs the O atom of methanol directionally, while negatively charged Cu/Co/Ni adsorb and accelerate the dissociation of H atoms. DFT calculations and AIMD simulations confirm that the methanol adsorption energy at La sites is more negative, with faster and more stable adsorption. The synergistic coupling of "adsorption-activation" significantly enhances catalytic efficiency. This study provides a novel guiding strategy for the design of high-performance, low-cost hydrogen production catalysts, which is of great significance for the sustainable development of hydrogen energy.