In this study, niobium diboride (NbB 2 ) was investigated using synchrotron radiation X-ray diffraction in a diamond anvil cell to analyze their compressive behavior at room temperature. The volume of the NbB 2 was fitted to its corresponding highest pressures of 32.2 GPa without experiencing structural phase transitions, leading to the determination of bulk modulus of 389(7) GPa. Additionally, we further investigated the bulk modulus, band structure and density of states of NbB 2 to 35 GPa by density functional theory. The results yielded a bulk modulus of 285 GPa for NbB 2 . Importantly, it was observed that NbB 2 demonstrates both metallic and non-magnetic properties throughout the pressure range. In addition, we studied the deviatoric stress of NbB 2 at high pressure using linewidth analysis method. It was found that NbB 2 can support a maximum differential stress of 14.2 GPa at the pressure of 17.3 GPa.
A synergetic approach of nanoconfinement coupling with in-situ formed nanocatalysts was developed to fabricate a novel and robust nano-LiBH 4 system. The nanoconfining scaffold exhibits an unparalleled 3D hierarchical architecture featuring micro-, meso-, and macro-pores assembled by 2D interconnected nanosheets that consist of 0D hollow nitrogen-doped carbon nanocages. This structure possesses an accumulated pore width of 7.79 nm, extremely high pore volumes of 3.16 cm 3 /g, and a theoretical loading capacity of 67.9 wt% for LiBH 4 . The in-situ formed NbB 2 species transformed from initial NbF 5 nanoparticles is confirmed as the final active nanocatalyst. It is worth mentioning that the defective N heteroatoms within the scaffold can serve the role of coordinating with Nb cations and weaken the B-H bonds as supported by the DFT calculations. With an optimized loading of 50 wt% LiBH 4 , the initial dehydrogenation temperatures can be reduced to 140.6 °C, and the system can rapidly release 7.55 wt% H 2 at 320 °C within 39 min. Furthermore, the nanoconfined system exhibits excellent low-temperature reversibility, retaining 93 % of its capacity after 20 cycles at 300 °C. This study provides innovative perspectives on the design of novel scaffold structures doped with defective heteroatoms for the nanoconfinement and synergetic catalysis of de/rehydrogenation for metal borohydrides.
Yingxue Du,Qihao Wang,Xingchao Zang,Weiping Xiao,Yingxia Zong,Xuyun Guo,Zexing Wu,Lei Wang
The development of efficient and durable bifunctional electrocatalysts for overall water splitting remains a key challenge for sustainable hydrogen production. In this study, a novel strategy is proposed to synergistically design boron vacancies and integrate Ru species into NbB 2 (Ru/RuO 2 -NbB 2 -v) by calcination and immersion methods. NbB 2 with its intrinsic high conductivity facilitates to electron transport and improves the reaction kinetics of the catalyst. The strategic introduction of abundant B vacancy and Ru species can expose numerous active sites and lower the reaction energy barriers in the materials, thereby enhancing the reactivity of the catalysts. Impressively, Ru/RuO 2 -NbB 2 -v exhibited superior hydrogen evolution reaction (HER) activity in wide pH range. In addition, Ru/RuO 2 -NbB 2 -v also exhibits good oxygen evolution reaction (OER) performance in acidic and alkaline. A self-assembled electrolyzer driven by simulated solar energy enables the conversion of solar energy into hydrogen energy. The work pioneers a defect-engineering and noble-metal-decoration strategy to transform metal borides into versatile electrocatalysts, offering a scalable pathway for clean energy technologies.
Xiulin Fan,Xuezhang Xiao,Lixin Chen,Xinhua Wang,Shouquan Li,Hongwei Ge,Qidong Wang
LiBH4–MgH2 system in a 2 : 1 molar ratio constitutes a representative reactive hydride composite (RHC) for hydrogen storage. However, sluggish kinetics and poor reversibility hinder the practical applications. To ease these problems, amorphous TiB2 and NbB2 nanoparticles were synthesized and employed as catalysts for the 2LiBH4–MgH2 system. Isothermal de-/rehydrogenation and temperature programmed mass spectrometry (MS) measurements show that amorphous TiB2 and NbB2 nanoparticles can significantly improve the hydrogen storage performance of the 2LiBH4–MgH2 system. 9 wt% hydrogen can be released within only 6 min for nanoTiB2-doped 2LiBH4–MgH2, while for the undoped composite limited hydrogen of 3.9 wt% is released in 300 min at 400 °C. The dehydrogenation activation energies for the first and second steps are dramatically reduced by 40.4 kJ mol−1 and 35.2 kJ mol−1 after doping with nanoTiB2. It is believed that TiB2 and NbB2 nanoparticles can first catalyze the dehydrogenation of MgH2, and then induce the decomposition of LiBH4 and meanwhile act as nucleation agents for MgB2, thereby greatly enhancing the kinetics of dehydrogenation. The present study gives clear evidence for the significant performance of transition metal boride species in doped RHCs, which is critically important for understanding the mechanism and further improving the hydrogen storage properties of RHCs.
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