Built-In Electronic Asymmetry in PdCu/Cu Heterostructures Drives Bias-Free Electrocatalytic Co-Valorization of Nitroaromatics and Aldehydes

Paired electrocatalysis offers a compelling route to atom-economical and energy-efficient chemical synthesis by coupling complementary redox half-reactions within a single process. Yet its practical implementation demands macroscopic reactor infrastructure whose inherent resistance and kinetic penalties erode the very efficiency gains the concept promises. Here, we report an interface-engineered PdCu/Cu heterostructure (PdCu/OD-Cu) in which the intrinsic work function difference between PdCu and Cu domains drives interfacial charge redistribution, establishing a built-in electronic asymmetry that simultaneously optimizes nitroaromatic reduction on PdCu domains and aldehyde oxidation on Cu domains. This asymmetry enforces directional internal electron flow that synchronizes both half-reactions without external circuits, ion-exchange membranes, or applied bias, reducing the effective anode–cathode separation from the centimeter scale of conventional electrolyzers to the nanometer scale of individual catalyst particles. Isotope-labeled differential electrochemical mass spectrometry establishes internal electrochemical electron transfer as the coupling mechanism, excluding transfer hydrogenation. The wireless platform achieves near-quantitative nitroaromatic conversion with aniline selectivity exceeding 95% and aldehyde oxidation yields exceeding 97%, outperforming conventional membrane-based H-cells operated under identical conditions, even when the latter are supplied with an external bias. These results establish work function mismatch-driven interfacial electronic asymmetry as a general design principle for paired electrocatalysis without an externally applied bias.