钴盐阴离子基团对Co-N-C催化剂电催化活性的影响

采用化学氧化法在苯胺聚合过程中分别加入钴(Co)为Co2+而阴离子基团为(C2H3O2)22-、Cl22-、(NO3)22-、SO42-及C2O42-的乙酸钴、氯化钴、硝酸钴、硫酸钴、草酸钴等钴盐,合成出不同聚苯胺-钴(PANI-Co)配位聚合物。然后将PANI-Co聚合物作为前驱体在N2气氛中900℃热处理,制备出氮掺杂的Co-N-C碳基催化剂。采用SEM、XRD、XPS、Raman等手段分析Co-N-C催化剂的形貌、结构、化学组成及化学价态,并采用电化学方法测试了Co-N-C催化剂的电催化活性。结果表明,Co盐的阴离子基团对Co-N-C催化剂的形貌影响不大,但对Co-N-C催化剂中表面化学组成及含量、碳结构、石墨化程度以及Co的价态影响较大,并且Co盐的阴离子基团会影响Co-N-C催化剂的电催化活性,其氧还原(ORR)活性按照(C2H3O2)22-Cl22-(NO3)22-SO42-C2O42-顺序降低。含(C2H3O2)22-和Cl22-阴离子的钴盐制备的Co-N-C催化剂具有较高的ORR活性,这可能源于其较高含量的石墨氮和吡啶氮。     

Ultrathin Co-N-C Layer Modified Pt–Co Intermetallic Nanoparticles Leading to a High-Performance Electrocatalyst toward Oxygen Reduction and Methanol Oxidation

The development of low platinum-based alloy electrocatalysts is crucial to accelerate the commercialization of fuel cells, yet remains a synthetic challenge and an incompatibility between activity and stability. Herein, a facile procedure to fabricate a high-performance composite that comprises Pt–Co intermetallic nanoparticles (IMNs) and Co, N co-doped carbon (Co-N-C) electrocatalyst is proposed. It is prepared by direct annealing of homemade carbon black-supported Pt nanoparticles (Pt/KB) covered with a Co-phenanthroline complex. During this process, most of Co atoms in the complex are alloyed with Pt to form ordered Pt–Co IMNs, while some Co atoms are atomically dispersed and doped in the framework of superthin carbon layer derived from phenanthroline, which is coordinated with N to form Co–N_x moieties. Moreover, the Co-N-C film obtained from complex is observed to cover the surface of Pt–Co IMNs, which prevent the dissolution and agglomeration of nanoparticles. The composite catalyst exhibits high activity and stability toward oxygen reduction reactions (ORR) and methanol oxidation reactions (MOR), delivering outstanding mass activities of 1.96 and 2.92 A mg_Pt⁻¹ for ORR and MOR respectively, owing to the synergistic effect of Pt–Co IMNs and Co-N-C film. This study may provide a promising strategy to improve the electrocatalytic performance of Pt-based catalysts.     

Co-N-C催化对甲基苯甲醇氨氧化合成对甲基苯腈

以不同金属Co、Mn、Fe、Ni的醋酸盐为金属活性组分,1,10-邻菲啰啉为氮源,Vulcan XC72R型碳粉为载体,通过浸渍法负载后在不同温度下焙烧得到系列M-N-C催化剂。采用TEM、EDS、XRD、XPS、TG等对催化剂的结构进行表征分析,以对甲基苯甲醇氨氧化一步合成对甲基苯腈为探针反应考察M-N-C催化剂的催化氨氧化性能。结果表明,800℃焙烧的Co-N-C催化剂能够形成Co-N活性中心,具有较好的催化性能。在氧气分压0.5 MPa、反应时间24 h、氨水用量0.7 mL和反应温度130℃时,对甲基苯甲醇转化率94.4%,对甲基苯腈选择性96.4%。     

Atomically dispersed Co atoms in nitrogen-doped carbon aerogel for efficient and durable oxygen reduction reaction

Developing non-noble-metal-based electrocatalysts as alternatives to replace Pt-based catalysts for oxygen reduction reaction (ORR) is crucial for large scale industrial application of fuel cells. Herein, we report a facile method to synthesize atomically dispersed Co atoms anchored on nitrogen-doped carbon aerogels with a 3D hierarchically porous network structure via F127-assisted pyrolysis of a phenolic resin/Co²⁺ composite and subsequent HCl etching treatment. HRTEM, AC-STEM, XRD, XPS, and Raman spectroscopy measurements demonstrate that Co atoms are homogeneously atomically dispersed on nitrogen-doped carbon aerogels within the porous structure by coordination with pyridinic-N. Among a series of samples, the Co-NCA@F127-1: 0.56 catalyst exhibits an enhanced ORR activity with onset potential (E_onset) of 0.935 V vs. RHE, the high diffusion limiting current density of 5.96 mA cm⁻² at 0.45 V, as well as an excellent resistance to methanol poisoning and good long-term stability in alkaline medium, comparable to the state-of-the-art Pt/C catalyst. This work may provide a novel and ingenious thought in the design and engineering of efficient and robust electrocatalysts based on single transition-metal atoms supported by nitrogen-doped carbon materials.