The design of cost-effective and highly active catalysts is a critical challenge. Inspired by the strong points of stability and conductivity of carbon nanotubes (CNTs), high catalytic activity of Co nanoparticles, and rapid ion diffusion and large accessible area of three-dimensional (3D) graphene, we demonstrate a novel strategy to construct a hierarchical hybrid structure consisting of Co/CoO_x nanoparticles-incorporated CNT branches onto the 3D reduced graphene oxide (rGO) architecture. The surface-modified 3D rGO by steam activation process has a large surface area and abundant defect sites, which serve as active sites to uniformly grow Co/CoO_x nanoparticles. Furthermore, the CNTs preserve their performance stably by encapsulating Co nanoparticles, while the uniformly decorated Co/CoO_x nanoparticles exhibit superior electrocatalytic activity toward oxygen evolution/reduction reaction due to highly exposed active sites. Employing the hybrid particle electrocatalyst, the seawater battery operates stably at 0.01 mA cm⁻² during 50 cycles, owing to the good electrocatalytic ability.

具有成本效益和高活性的催化剂的设计是一个严峻的挑战。受到碳纳米管（CNT）的稳定性和导电性，Co纳米颗粒的高催化活性以及离子快速扩散和三维（3D）石墨烯的可及区域大的启发，我们展示了构建分层混合体的新策略由掺有Co / CoO _x纳米颗粒的CNT组成的结构分支到3D还原氧化石墨烯（rGO）结构上。通过蒸汽活化过程进行表面改性的3D rGO具有较大的表面积和丰富的缺陷位点，这些缺陷位点是均匀生长Co / CoO _x的活性位点纳米粒子。此外，CNT通过包封Co纳米颗粒而稳定地保持其性能，而均匀装饰的Co / CoO _x纳米颗粒由于高度暴露的活性位而表现出对氧释放/还原反应的优异电催化活性。由于具有良好的电催化能力，因此使用杂化颗粒电催化剂，海水电池在50个循环中可稳定地在0.01 mA cm ^-2下运行。