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Sodium borohydride (NaBH 4) hydrolysis is considered as a promising hydrogen production strategy. The key to accelerating NaBH 4 hydrolysis is the development of efficient catalysts. Metal-modified cobalt boride has demonstrated superior catalytic activity for NaBH 4 hydrolysis compared to pure cobalt boride. However, the relationship between the high activity of metal-modified cobalt boride and the modifying metal has not been summarized. In this work, through extensive literature research, the mechanisms of metal modification on the catalytic activity improvement of metal-modified cobalt boride were clarified, the reaction mechanisms of NaBH 4 hydrolysis catalyzed by cobalt boride and metal-modified cobalt boride were compared and analyzed, the challenges metal-modified cobalt boride may encounter in the future study of NaBH 4 hydrolysis were discussed, and our recommendations were provided. This work can provide an important theoretical basis for the design and development of efficient and robust catalysts, as well as for the advancement of hydrogen production technology. • Metal-modified cobalt boride (Co-M-B) for NaBH 4 hydrolysis was overall reviewed. • The mechanism of catalytic activity enhancement of Co-M-B was clarified. • Challenges that Co-M-B may encounter in future development were proposed. [ABSTRACT FROM AUTHOR]

In the reaction system with NaBH 4 as a hydrogen donor, inhibiting the formation of hydrogen is the key to promote the efficient catalytic hydrogenation of CO 2. In this study, nanoscale zero-valent nickel supported on carbon nanofibers (Ni0/CNFs) was fabricated as a catalyst for CO 2 hydrogenation in aqueous NaBH 4 solution. The characteristics of Ni0/CNFs were examined. By SEM, it was observed that spherical nickel nanoparticles were distributed homogeneously on the surface of strip-shaped carbon nanofibers. EDS mappings indicated that elements were evenly distributed on the catalyst, which might contribute to the uniform exposure of active sites. Via XRD, it was determined that all the diffraction peaks corresponded to the crystal face of nickel metal and that the absence of diffraction peaks of carbon nanofibers indicated that the crystallinity of the carrier was low. XPS study showed that nickel existed on the catalyst surface in two forms: zero valence metal and oxidation state. The effects of catalyst addition amount, NaBH 4 concentration, NaOH dosage, stirring rate on the yield of formate and hydrogen generation rate (HGR) were investigated. By optimizing the above parameters, the concentration of formate reached 150 mmol/L and the hydrogen production rate was 10.55 mL/min. Compared with the non-catalytic conditions, the concentration of formate increased by 57 % and the HGR decreased by 78 %. Moreover, the relationship between CO 2 hydrogenation and NaBH 4 hydrolysis was clarified. This research could enhance comprehension of CO 2 hydrogenation in aqueous NaBH 4 solution and contribute to the development of CO 2 capture and utilization storage technology. The significance of this study lies in clarifying the connection between CO 2 hydrogenation and borohydride hydrolysis in CO 2 catalytic hydrogenation technology. • Ni0/CNFs promoted CO 2 catalytic hydrogenation by inhibiting NaBH 4 hydrolysis. • The relationship between CO 2 hydrogenation and NaBH 4 hydrolysis was clarified. • Catalytic hydrogenation of CO 2 was performed under ambient conditions. [ABSTRACT FROM AUTHOR]