This paper considers how to use a group of robots to sense and control a diffusion process. The diffusion process is modeled by a partial differential equation (PDE), which is a both spatially and temporally variant system. The robots can serve as mobile sensors, actuators, or both. Centroidal Voronoi Tessellations based coverage control algorithm is proposed for the cooperative sensing task. For the diffusion control problem, this paper considers spraying control via a group of networked mobile robots equipped with chemical neutralizers, known as smart mobile sprayers or actuators, in a domain of interest having static mesh sensor network for concentration sensing. This paper also introduces the information sharing and consensus strategy when using centroidal Voronoi tessellations algorithm to control a diffusion process. The information is shared not only on where to spray but also on how much to spray among the mobile actuators. Benefits from using CVT and information consensus seeking for sensing and control of a diffusion process are demonstrated in simulation results.