表面富集的超小铂纳米颗粒耦合缺陷磷化钴用于高效的电催化水分解和柔性锌空气电池

Surface-enriched ultrafine Pt nanoparticles coupled with defective CoP as efficient trifunctional electrocatalyst for overall water splitting and flexible Zn-air battery

开发多功能的纳米电催化剂可以提高单位催化剂表面活性密度.本课题组采用热解和还原工艺制备了具有多功能电催化性能的超小铂纳米颗粒耦合缺陷CoP的纳米材料(Pt/d-CoP/NPC),它具有较高的氧还原反应(ORR)半波电位(0.82 V).所合成的Pt/d-CoP/NPC电催化剂具有良好的电催化析氢反应活性,当反应活性达到10 mA cm^(-2)时,过电位分别为33 mV@1mol/L KOH, 10 mV@0.5 mol/L H_(2)SO_(4)和70 mV@1 mol/L PBS.Pt/d-CoP/NPC催化剂还表现出较好的析氧反应活性.以合成的催化剂Pt/d-CoP/NPC作为电极组装的全解水装置和可充电锌空气电池具有良好的活性和稳定性,可以持续有效地驱动全解水产氢,在存储可再生能源方面的具有较好的应用潜力.采用X射线光电子能谱(XPS)、拉曼光谱测试和傅里叶红外光谱测试(FTIR)等技术研究了Pt颗粒与CoP之间的相互作用,并利用密度泛函理论(DFT)计算研究了催化剂的ORR反应机制.Pt/d-CoP/NPC在129.3 (2p_(3/2))和130.1 eV (2p_(1/2))处的P 2p轨道观察到P-M键,证实了金属磷化物的存在.Pt/d-CoP/NPC的Co结合能相对于d-CoP/NPC的结合能发生了正移,表明Pt与CoP之间存在电子相互作用.由于Co和Pt的电负性差异,Pt/d-CoP/NPC中Pt的峰值与商用Pt/C相比呈负移,说明电子从Co向Pt转移.XPS也证实了碳的存在.此外,拉曼光谱也出现了碳的特征峰D峰和G峰.并且Pt/d-CoP/NPC和d-CoP/NPC的ID/IG值相似,说明Pt的引入不会影响碳基体的结构.在N 1s光谱中,检测到N-P和吡啶氮的存在,证实在Pt/d-CoP/NPC和d-CoP/NPC中形成了N, P掺杂的碳.此外, Pt/d-CoP/NPC的FTIR谱出现对应于P-O, N-P, C-C, C-H和O-H的峰,也证明了氮磷共掺杂碳的存在.通过DFT计算进一步分析Pt/d-CoP/NPC电催化剂具有良好ORR活性的原因.结果表明,电荷从CoP转移到Pt,有利于活性氧分子的活化,促进催化过程.对比不同模型ORR过程中间体的自由能图, Pt/d-CoP/NPC和Pt/C的速率决定步骤为O_(2)生成OOH^(*),合成的Pt/d-CoP/NPC具有有利的热力学过电位,证明了其高效的ORR性能.此外, Pt/d-CoP/NPC中Pt的d带中心相对于纯Pt有明显的正向费米能级转移,说明引入的CoP可以导致离域电子重分布,从而优化了反应中间体的吸附.综上,Pt/d-CoP/NPC催化剂中Pt与CoP之间存在相互作用,进而提高催化活性,该催化剂的合成有望为开发多功能电催化纳米材料提供参考.

Developing multifunctional electrocatalysts toward energy-related reactions could reduce the cost and improve the utilization efficiency of raw materials. Herein, defective CoP decorated with ultrafine Pt nanoparticles(Pt/d-CoP/NPC) with multifunctional electrocatalytic performances is prepared via facile pyrolysis and following chemical reduction process. The as-synthesized Pt/d-CoP/NPC owns high half-wave potential of 0.82 V for oxygen reduction reaction with excellent stability in 0.1 mol/L KOH. Density functional theory calculations demonstrate that the adsorption energy of ^(*)OO at Pt/d-CoP/NPC is stronger compared to Pt, yielding higher catalytic activity for ORR. Moreover, the resultant electrocatalyst possesses excellent catalytic activities with low overpotentials toward hydrogen evolution reaction(33 mV in 1 mol/L KOH, 6 mV in 0.5 mol/L H_(2)SO_(4) and 70 mV in 1 mol/L PBS) and oxygen evolution reaction(320 mV) at 10 mA/cm^(2). Water-splitting and rechargeable Zn-air batteries assembled with the as-synthesized Pt/d-CoP/NPC as electrodes exhibit outstanding activity and long-range stability. Remarkably, sustainable energies and homemade Zn-air battery can efficiently drive the Pt/d-CoP/NPC electrolyzer with sumless hydrogen bubbles generated, verifying the potential applications for renewable energy storage.