Breaking the stability-activity trade-off in single-atom catalysis via interlayer electric fields in van der Waals heterostructure †

Abstract

Single-atom catalysts (SACs) offer exceptional metal utilization efficiency and unique tunability of electronic structure at the atomic scale; however, their practical deployment is severely limited by intrinsic instability arising from metal aggregation and electrochemical dissolution. Here, we present a unified computational strategy based on first-principles density functional theory (DFT) to simultaneously address stability and catalytic activity in SACs. By integrating transition metal SACs embedded in nitrogen-doped graphene (M@NGr) with monolayer MoS2 or Nb-doped p-type MoS2 (p-MoS2) to form van der Waals heterostructures, spontaneous interlayer charge transfer—driven by work function mismatch—generates a built-in electric field directed from M@NGr toward the transition metal dichalcogenide layer. This intrinsic electric field electrostatically anchors the positively charged SAC metal atoms within their nitrogen-coordinated binding sites, markedly suppressing both thermodynamic aggregation and electrochemical dissolution across a broad range of 3d, 4d, and 5d transition metals. Concurrently, hybridization between the metal dz2 orbital and the nearest chalcogen pz states—induced by the same interfacial electronic coupling—delocalizes the dz2 electron density and systematically weakens metal-hydrogen bonding, shifting the hydrogen adsorption free energy (∆GH*) toward thermoneutral values. Both effects are substantially amplified in M@NGr/p-MoS2 system, where Nb substitution increases the work function mismatch and drives greater interlayer charge transfer. Among all systems investigated, Ru@NGr/p-MoS2 achieves the most favorable combination of thermodynamic stability and near-thermoneutral ∆GH*, identifying it as a highly promising electrocatalyst for the hydrogen evolution reaction under acidic conditions. These findings establish interlayer charge transfer-induced electric field engineering as a general, broadly applicable design principle for simultaneously robust and active SAC development.