【作者】 陈家宝；

【导师】 李海波；

【作者基本信息】 聊城大学 ， 无机化学， 2023， 硕士

【摘要】 随着化石燃料的急剧消耗和环境问题的日益严峻,清洁、高效、可持续的能源转换和储存装置受到全球学术界的广泛关注。锌-空气电池（ZABs）具有方便、高效、无污染、放电电压平稳、安全稳定、比容量高等优点,但其阴极氧还原反应（ORR）涉及到多步中间体的转化,导致反应动力学缓慢。因此,开发高活性、强稳定性的ORR催化剂成为当前面临的挑战。本论文通过非贵金属掺杂修饰Pd基催化剂,调控Pd的电子结构,提高其催化活性、稳定性和抗甲醇能力,并针对ZABs的应用展开研究。主要包含以下三部分:1.Pd/Fe双金属掺杂碳基催化剂电催化氧还原研究及其在锌-空气电池中的应用本研究通过一步热解植酸、三聚氰胺和Pd/Fe的金属盐合成双金属Pd/Fe-N-C催化剂。Pd/Fe-N-C催化剂的半波电位(E_1/2)为0.84 V,质量活度为372 m A mg_Pd^-1,可达商业Pt/C的2.1倍。其催化稳定性和甲醇耐受性均优于商业Pt/C催化剂。研究结果表明,Pd-N_x为催化剂的活性中心,Fe组分引入能够进一步提升Pd/Fe-N-C的ORR催化性能。将其作为阴极催化剂组装ZABs时,比容量为～775 m Ah g_Zn^-1。同时,其峰值功率密度可达3.85 W mg_Pd^-1,是商业Pt/C催化剂(1.13 W mg_Pt^-1)的3.4倍。2.具有高氧还原活性Pd Sn@NPC催化剂的制备及其在锌-空电池的应用以三聚氰胺和植酸为碳源、氮源和磷源,经碳化后制备得到具有多孔结构的碳载体。然后以KBH₄为还原剂在碳载体上还原Pd/Sn盐,再经高温处理后得到Pd_xSn_y@NPC催化剂。金属Pd经Sn掺杂形成Pd Sn合金,可对Pd的局域电子结构进行调节,降低d能带中心以提高ORR催化活性。优化合成条件后得到的Pd₁Sn₃@NPC催化剂表现出良好的ORR活性,其半波电位(E_1/2)为0.87 V（vs.RHE）,与商业Pt/C(E_1/2=0.86 V)相当。催化剂在0.87 V电位下的质量活度为260 m A mg_Pd^-1,约为Pt/C(140 m A mg_Pt^-1)的1.86倍。在电流密度为322 m A cm^-2时,以Pd₁Sn₃@NPC为阴极催化剂的ZABs的峰值功率密度达到213 m W cm^-2,与商业Pt/C性能相近。3.基于ZIF-8构筑Pd Zn有序合金氧还原催化剂及其在锌-空气电池中的应用采用MOF作为前驱体与聚合物包覆策略相结合的方法,以ZIF-8作为载体,KBH₄为还原剂在碳载体上还原金属Pd,再以多巴胺聚合包覆在表面后碳化,合成了Pd₂Zn-NC-900催化剂。得益于形成的Pd Zn有序合金结构,该催化剂显示出良好的ORR催化活性和稳定性,其E_1/2为0.88 V（vs.RHE）、并且在5000次循环伏安（CV）测试后,仅存在2 m V的电位损失。将Pd₂Zn-NC-900作为阴极催化剂组装成的ZABs在变电流放电时电压高于商业Pt/C,并且具有814.3 m Ah g_Zn^-1的高比容量和213.7 m W cm^-2的高峰值功率密度。更多还原

【Abstract】 With the rapid consumption of non-renewable energy and environmental pollution,the situation is becoming more and more serious,the development of clean,efficient and sustainable energy conversion and storage devices has attracted extensive attention from the global academic community.Metal-air batteries have many advantages,such as convenience,high efficiency,pollution-free,stable discharge voltage,high specific capacity,safety and stability.However,many intermediates and reaction obstacles are involved in the cathodal oxygen reduction reaction（ORR）of metal-air batteries,resulting in slow kinetics,which poses a challenge to the development of highly active and stable ORR catalysts.In this paper,Pd-based catalysts were prepared by non-noble metal doping.By adjusting the electronic structure of Pd,the catalytic activity,stability and methanol resistance of the catalyst were improved.It mainly includes the following three parts:1.Study on electrocatalytic oxygen reduction over Pd/Fe bimetal doped carbon-based catalyst and its application in Zinc-air batteries.In this system,Pd/Fe-N-C bimetallic catalyst was prepared by one step pyrolysis of phytic acid,melamine and Pd/Fe-based salts.The half-wave potential(E_1/2)of Pd/Fe-N-C catalyst was 0.84 V,and the mass activity was 372 m A mg_Pd^-1,up to 2.1 times that of commercial Pt/C.It turns out that Pd-N_x was the active center of the catalyst,and the introduction of Fe components could further improve the ORR performance of Pd/Fe-N-C.Its catalytic stability and methanol tolerance were better than those of commercial Pt/C catalysts.When it was used as cathode catalyst to assemble into Zinc-air cell,its specific capacity was～775 m Ah g_Zn^-1.Meanwhile,the peak power density can reach 3.85 W mg_Pd^-1,which is 3.4 times of the commercial Pt/C catalyst(1.13 W mg_Pt^-1).2.Preparation of Pd/Sn@NPC catalyst with high oxygen reduction activity and its application in Zinc-air battery.Melamine and phytic acid were used as carbon,nitrogen and phosphorus sources to synthesize carbon carriers with porous structure after carbonization.Then,Pd and Sn were reduced on the carbon support using KBH₄ as reducing agent,followed by high temperature treatment to obtain Pd_xSn_y@NPC.The metal Pd was doped with Sn to form a Pd Sn alloy,which changed the electronic structure of Pd,reduced the D-band electron center,and improved the ORR catalytic activity.The Pd₁Sn₃@NPC catalyst obtained after optimization of the synthesis conditions showed good ORR activity.Its half-wave potential of 0.87V（vs.RHE）is similar to that of commercial Pt/C(E_1/2=0.86V).The mass activity at 0.87 V potential is 260 m A mg_Pd^-1,about 1.86 times of Pt/C(140 m A mg_Pt^-1).At a current density of 322 m A cm^-2,the Zn-air battery with Pd₁Sn₃@NPC as cathode catalyst achieves a peak power density of 213 m W cm^-2,which is similar to commercial Pt/C performance.3.Construction of Pd Zn ordered alloy oxygen reduction catalyst based on ZIF-8 and its application in Zinc-air battery.Pd₂Zn-NC-900 bimetallic catalyst was synthesized by combining the MOF precursor method with the polymer coating strategy,using ZIF-8 as the support,KBH₄ as the reducing agent to reduce metal Pd on the carbon support,and then using dopamine polymerization to coat the surface and carbonize.Thanks to the formed Pd Zn ordered alloy structure,the catalyst showed good ORR activity and stability with a E_1/2 of 0.88 V（vs.RHE）and a decrease of only2 m V after testing 5000 cyclic voltammetry（CV）cycles.The ZABs assembled with Pd₂Zn-NC-900 as cathode catalyst has a higher discharge voltage than commercial Pt/C.It has a high specific capacity of 814.3 m Ah g_Zn^-1 and a peak power density of 213.7 m W cm^-2.更多还原