Liang Chenxi, Wang Zhenbin, Zhang Mingjin, Ma Cunhua
School of Chemistry and Chemical Engineering, Qinghai Normal University Xining 810008 China
Academy of Plateau Science and Sustainability, People's Government of Qinghai Province & Beijing Normal University Xining 810016 China.
RSC Adv. 2024 Jul 31;14(33):23930-23942. doi: 10.1039/d4ra03460k. eCollection 2024 Jul 26.
Magnesium hydroxide (MgH) has a broad application prospect in solid hydrogen storage, but the associated higher dehydrogenation temperature and undesirable cycling capacity limit its large-scale application. In this study, a BaCrO nanocatalyst prepared a wet chemistry method was added to MgH to achieve better kinetic and thermodynamic performances. Kinetic tests suggested that the onset hydrogen desorption temperature was decreased for milled MgH from 390 °C to below 280 °C after the introduction of a 5 wt% BaCrO nanocatalyst and the maximum dehydrogenation amount was up to 6.32 wt%. With regard to hydrogen absorption, MgH incorporated with 10 wt% BaCrO could fully absorb 5.78 wt% H within 10 min at 300 °C and recharge 3.1 wt% H at a low temperature of 250 °C. In comparison, the hydrogen uptake amounts for MgH under the same conditions were only 3.98 wt% and 1.52 wt%. With regard to hydrogen desorption, 5 wt% BaCrO-modified MgH could discharge 4.25 wt% H within 10 min at 325 °C and 4.81 wt% H at 300 °C, while MgH could not dehydrogenate at 300 °C. Meanwhile, only 5% of the performance decayed for 5 wt% BaCrO-modified MgH during ten cycles. Dehydrogenation reduced to 106.75 kJ mol in contrast to 156.55 kJ mol for MgH. In addition, DFT results verified that the BaCrO nanocatalyst reduced the band gap from 2.78 eV to 2.16 eV to improve the thermodynamic property of MgH and contributed to the decrease in the dehydrogenation energy barrier from 2.27 eV to 1.54 eV. This work provides an insight into the performance of ternary transition metal nanocatalysts for MgH hydrogen storage systems.
氢氧化镁（MgH）在固体储氢领域具有广阔的应用前景，但相关的较高脱氢温度和不理想的循环容量限制了其大规模应用。在本研究中，通过湿化学方法制备的BaCrO纳米催化剂被添加到MgH中，以实现更好的动力学和热力学性能。动力学测试表明，在引入5 wt%的BaCrO纳米催化剂后，球磨后的MgH的起始氢解吸温度从390℃降至280℃以下，最大脱氢量高达6.32 wt%。关于氢吸收，掺入10 wt% BaCrO的MgH在300℃下10分钟内可完全吸收5.78 wt%的H，并在250℃的低温下再充入3.1 wt%的H。相比之下，相同条件下MgH的氢吸收量仅为3.98 wt%和1.52 wt%。关于氢解吸，5 wt% BaCrO改性的MgH在325℃下10分钟内可释放4.25 wt%的H，在300℃下可释放4.81 wt%的H，而MgH在300℃下不能脱氢。同时，5 wt% BaCrO改性的MgH在十个循环中性能仅衰减5%。脱氢能降至106.75 kJ/mol，而MgH为156.55 kJ/mol。此外，密度泛函理论（DFT）结果证实，BaCrO纳米催化剂将带隙从2.78 eV降低到2.16 eV，以改善MgH的热力学性质，并有助于将脱氢能垒从2.27 eV降低到1.54 eV。这项工作为三元过渡金属纳米催化剂在MgH储氢系统中的性能提供了深入了解。
