钴基催化剂催化NaBH_(4)制氢研究进展

Hydrogen Generation from Sodium Borohydride by Co-based Catalysts:a Review

氢气是清洁燃料,不会对环境产生任何有毒副产品,且氢气具有很高的能量密度,约为120 kJ/g,比石油的三倍还多,是燃料电池理想的替代能源载体。未来,氢气具有广阔的发展空间和应用前景,但氢的存储安全问题需要进一步解决,而化学储氢对实现这一目标起着至关重要的作用。NaBH_(4)作为储氢材料,其氢含量高达10.7%(质量分数),远高于其它化学品,且NaBH_(4)溶液可长期贮存,在有催化剂的情况下,其放氢速率可得到控制。虽贵金属催化剂具有优越的催化活性和稳定性,但由于资源有限且成本高,研究人员开始重点研究非贵金属催化剂。其中,钴基催化剂,因其活性高、比贵金属便宜以及储量丰富等优点而受到越来越多的关注,具有广阔的商业应用前景。然而钴的弱点之一是由于硼酸盐的强吸附作用使其表面钝化而失活,通过与金属合金化可以改变钴的电子结构,减少钴的吸附。钴基催化剂主要分为载体型催化剂和无载体型催化剂。无载体钴基催化剂表面积通常较小,且其在放热水解反应中容易团聚,导致催化性能降低和使用寿命减短。因此钴基活性组分通常负载于载体上,由于金属钴与催化剂载体间存在强相互作用以及与其它元素间的协同效应,使得钴基催化剂在硼氢化钠水解制氢过程中表现出较高的催化活性。此外,加入掺杂剂如B或P,以及与另一种过渡金属(Ni、Fe、Cu、Mo、Zn、W和Cr等)或稀土金属(Ce、Pr和La等)合金化也可以提高其催化效能。钴基催化剂有很多种,包括钴纳米颗粒、金属钴、钴盐及氧化钴等。本文综述了钴基催化剂用于催化NaBH_(4)水解的研究进展,主要包括NaBH_(4)水解原理、实验室测定NaBH_(4)水解制氢常用装置、钴基催化剂制备方法、钴基催化剂分类及钴基催化剂用于催化NaBH_(4)水解的影响因素;重点介绍了钴基-载体型催化剂催化NaBH_(4)水解制氢的研究进展,提出了目前钴基催化剂发展面临的问题并对未来钴基催化剂研究的发展方向进行了展望。

Hydrogen is the cleanest fuel because it does not produce any toxic by-products to the environment and has a high energy density of 120 kJ/g,more than three times higer than that of oil.It is an ideal alternative energy carrier for fuel cell and has broad prospects for development and application in the near future.As a hydrogen storage medium,NaBH_(4) contains hydrogen with a mass fraction of 10.7%,which is much higher than other chemicals,and its solution can be stored for a long time.In the presence of a catalyst,the rate of hydrogen release can be controlled.Although precious metal catalysts have high activity and stability,the researchers focused on non-precious metal catalysts due to limited resources and high costs.Cobaltbased catalysts have broad commercial application prospects due to their high activity,lower cost than precious metals and more abundant reserves.However,one of the weaknesses of cobalt is the passivation and deactivation of borate due to its strong adsorption.The electronic structure of cobalt can be modified by alloying in order to reduce cobalt adsorption.Cobalt-based catalysts are mainly divided into supported catalysts and unsupported catalysts.The surface area of unsupported cobalt-based catalysts is usually small,and it is easy to agglomerate in the exothermic hydrolysis reaction,resulting in reduced catalytic performance and service life.Therefore,the cobalt-based active ingredients are usually carried on the carrier.Due to the strong interaction between the metal cobalt and the catalyst carrier,and the synergistic effect with other elements,the cobalt-based catalyst exhibits a higher performance in the process of hydrogen production by the hydrolysis of sodium borohydride.In addition,adding dopants such as B or P,and alloying with other transition metals(Ni,Fe,Cu,Mo,Zn,W,Cr,etc.)or rare earth metals(Ce,Pr,La,etc.)can also improve its catalytic performance.There are many kinds of cobalt-based catalysts,including cobalt nanoparticles,metallic cobalt,cobalt salts,and cobalt oxides.This paper reviews the research progress of cobalt-based catalysts used to catalyze the hydrolysis of NaBH_(4) including the hydrolysis principle of NaBH_(4),the classification of cobalt-based catalysts and the influencing factors of cobalt-based catalysts used to catalyze the hydrolysis of NaBH_(4).It focuses on the research progress of cobalt-based supported catalysts,and puts forward the current problems in the development of cobaltbased catalysts and prospects for the future development of cobalt based catalysts.