The two-dimensional Dion-Jacobson (DJ) perovskite HPrNb2O7 (HPNO) has emerged as a promising catalyst for NH3 decomposition under mild conditions, yet the atomistic origin of the reported thermal activity remains unclear. Here, message-passing Atomic Cluster Expansion, density functional theory (DFT), and ab initio molecular dynamics (AIMD) are integrated to connect HPNO proton topology with thermal effects, including the emergence of thermally activated surface defects and a thermally induced, reaction-promoting microenvironment within the interlayer. We first identify the energetically preferred proton site within the bulk, resolving the long-term experimental ambiguity, and link the validated topology to the intrinsic Brønsted acidity of HPNO, using Bader charge analysis, projected density of states, and electron localization functions. Building on this baseline, potential energy surface calculations on the HPNO surface illustrate that thermally accessible defects, together with the surface O-H⋯O units, drive the dynamical tilting of reaction-relevant octahedral pairs, reshaping the energy landscape by lowering N-H activation barriers and enabling associative Mars-van Krevelen routes. Within the HPNO interlayer, DFT and AIMD simulations verify that ammonia molecules can be absorbed and remain stabilized under thermal fluctuations by the Brønsted-acid sites and interlayer van-der Waals interactions. The thermally activated proton transfer is further revealed by AIMD trajectories, creating a confined microenvironment conducive to N-N coupling. Overall, as an early-stage investigation, this work pinpoints the mechanistic origins of HPNO’s thermally promoted reactivity toward NH3 decomposition. It also clarifies the critical roles of proton topology, defect engineering, and the interlayer chemical environment in governing catalytic activity over DJ perovskite catalysts.
34 Chemical Sciences
,3406 Physical Chemistry
,3407 Theoretical and Computational Chemistry
