Frontier Orbital Engineering of the Oxide Photocatalyst K2Zn2Nb4O13 by Coupling Crystal Structure, Electronic Structure, and Chemical Bonding

Abstract

Rational design of oxide photocatalysts with intrinsically efficient bulk carrier transport remains a major challenge because carrier migration is strongly governed by the complex interplay among crystal structure, electronic structure, and chemical bonding. Here, we propose a Frontier orbital engineering strategy to regulate intrinsic carrier transport by reconstructing the Frontier orbital composition within a structurally robust oxide framework. Based on the tunnel-type Na2Ti6O13 structure, the oxide semiconductor K2Zn2Nb4O13 was designed and synthesized through the cooperative substitution of Ti4+ by Zn2+/Nb5+. Combined high-resolution PXRD and NPD refinements confirm the successful realization of the designed tunnel framework with complete Zn/Nb ordering. Orbital-resolved electronic structure and chemical bonding analyses demonstrate that the valence band maximum (VBM) and conduction band minimum (CBM) are mainly derived from Zn 3d−O 2p and Nb1 4d−O 2p antibonding orbitals, respectively. Such orbital decoupling of Frontier orbital contributing units and the continuous covalent networks along the b-axis provide favorable pathways for bulk carrier migration and establish the structural and electronic basis for the proposed Frontier orbital engineering strategy. Experimentally, Pd-loaded K2Zn2Nb4O13 exhibits enhanced photocatalytic H2 generation activity, achieving a rate of 119(3) μmol/h. This work provides Frontier orbital engineering as a design paradigm for functional materials, enabling the rational manipulation of intrinsic charge transport properties through the synergistic regulation of crystal structure, electronic structure, and chemical bonding.