Nullnorms as a generalization of the concepts of t-norms and t-conorms admit a zero element to be any element in a bounded lattice. In this paper, we discuss the characterization of idempotent nullnorms on bounded lattices and investigate some of the main properties of them. We propose some new methods yielding nullnorms, in particular idempotent nullnorms, on bounded lattices with the fixed zero element under some additional constraints. Moreover, some illustrative examples are presented to demonstrate the feasibility of the proposed methods. (C) 2019 Elsevier B.V. All rights reserved.