Li Xue-Cheng, She Fa-Shuang, Shen Dong, Liu Chao-Ping, Chen Li-Hua, Li Yu, Deng Zhao, Chen Zhen-Hua, Wang Hong-En
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology 122 Luoshi Road, Hongshan District Wuhan 430070 China
Department of Chemistry and Center of Diamond and Advanced Films (COSDAF), City University of Hong Kong HKSAR China.
RSC Adv. 2018 Aug 10;8(50):28625-28631. doi: 10.1039/c8ra04256j. eCollection 2018 Aug 7.
Cost-effective and efficient electrocatalysts for the oxygen reduction reaction (ORR) are crucial for fuel cells and metal-air batteries. Herein, we report the facile synthesis of a Co/CoO/CoO heterostructure embedded in a porous carbon matrix by refluxing and annealing. This composite exhibits several structural merits for catalyzing the ORR: (1) the existence of metallic Co and graphitic carbon enhanced the electrical conduction; (2) the porous, loose carbon network facilitated the electrolyte permeation and mass transport; (3) more importantly, the nanosized coherent CoO/CoO heterojunctions with structural defects and oxygen vacancies enhanced the charge transport/separation at the interface and adsorption affinity to O, thus promoting the ORR kinetics and lowering the reaction barrier. Consequently, the composite electrode manifests high electrocatalytic activity, attaining a current density of 6.7 mA cm at -0.8 V ( Ag/AgCl), which is superior to pure CoO nanoparticles (4.7 mA cm), and has good methanol tolerance. The present strategy based on heterostructure and vacancy engineering may pave the way for the exploration of more advanced, low-cost electrocatalysts for electrochemical reduction and evolution processes.
用于氧还原反应（ORR）的具有成本效益且高效的电催化剂对于燃料电池和金属空气电池至关重要。在此，我们报道了通过回流和退火简便合成嵌入多孔碳基质中的Co/CoO/CoO异质结构。这种复合材料在催化ORR方面表现出几个结构优点：（1）金属Co和石墨碳的存在增强了导电性；（2）多孔、疏松的碳网络促进了电解质渗透和质量传输；（3）更重要的是，具有结构缺陷和氧空位的纳米级相干CoO/CoO异质结增强了界面处的电荷传输/分离以及对O的吸附亲和力，从而促进了ORR动力学并降低了反应势垒。因此，复合电极表现出高电催化活性，在-0.8 V（Ag/AgCl）时达到6.7 mA cm的电流密度，优于纯CoO纳米颗粒（4.7 mA cm），并且具有良好的甲醇耐受性。基于异质结构和空位工程的当前策略可能为探索用于电化学还原和析氧过程的更先进、低成本的电催化剂铺平道路。
