Charge‐Decoupled Functional Switching in 2D / 3D Integrated Heterostructure Electrodes for Dual‐Mode Electrochemical and Photoelectrochemical Hydrog

ABSTRACT

Electrochemical and photoelectrochemical hydrogen production are often pursued separately, even though both ultimately require electron consumption at the catalyst–electrolyte interface to form H ₂ . Integrating light harvesting, charge transport, and catalysis within a single photoelectrode can impose intrinsic trade‐offs. Here, we propose a charge‐decoupled electrode architecture that enables dual‐mode electrochemical and photoelectrochemical hydrogen production by separating charge generation from charge consumption within one platform. Vertically aligned n‐type GaN nanorods grown on silicon provide an electrically continuous pathway for charge transport and, under illumination, a source of photocarriers, while a continuous two‐dimensional TiS ₂ layer functions as an efficient interfacial charge transfer layer and the hydrogen‐evolution‐active interface. In electrochemical operation, externally supplied electrons are delivered through n‐GaN and consumed at the TiS ₂ surface to produce hydrogen at the working electrode. Under photoelectrochemical operation, photocarriers generated in n‐GaN are separated at the TiS ₂ /n‐GaN junction, and the electrode operates in photocathodic mode to drive proton reduction and hydrogen production at the illuminated working‐electrode surface. These results demonstrate charge‐decoupled functional switching and highlight its potential as an electrode‐architecture principle for carbon‐neutral hydrogen production across electrochemical and photoelectrochemical regimes.

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