Hierarchical nanoporous (HNP) PtTi alloy with multimodal size distributions and controllable bimetallic ratio is successfully fabricated by a simple two-step dealloying process. The as-prepared HNP-Pt75Ti25 alloy consists of interconnected bimodal nanoporous architecture with two order ligament/pore size distributions and interconnected hollow channels extending in all three dimensions. Compared with the NP-Pt and commercial Pt/C catalysts, HNP-Pt75Ti25 alloy exhibits markedly enhanced electrocatalytic activities for oxygen reduction reaction (ORR) with superior catalytic durability besides the higher specific and mass activities. Xray photoelectron spectroscopy and density functional theory calculations demonstrate that alloying Pt with Ti (25 at.%) could bring favorable electronic perturbation with the downshifted d-band center of Pt, leading to the weakened Pt-O and Pt-OH bond as well as the improved ORR performances. The excellent electrocatalytic performances for ORR and the facile preparation render HNP-Pt75Ti25 alloy attractive as promising cathode electrocatalysts in proton exchange membrane fuel cells. (C) 2015 Elsevier B.V. All rights reserved.