Unbiased Hydrogen Generation Driven by a Band‐Engineered Single GeSe Photoelectrode Delivering Over 10 mA cm −2

ABSTRACT Photoelectrocatalytic water splitting requires high photovoltage, making unbiased operation with a single light absorber difficult. Here, we employ band‐engineered GeSe as a photocathode for low‐bias hydrogen production and replace the sluggish oxygen evolution reaction (OER) with the ethanol oxidation reaction (EOR) to minimize the anodic potential. Introducing a Zn 0.5 Cd 0.5 S buffer layer establishes a type‐II band alignment (ΔE CBM ≈ −0.18 eV) that suppresses interfacial recombination and markedly improves charge extraction. The optimized GeSe photocathode delivers −12.42 mA cm −2 at 0 V RHE . Coupled with a low‐potential EOR anode, the system achieves, for the first time, unbiased hydrogen evolution driven by a single GeSe photoelectrode, sustaining a working current density of 11.34 mA cm −2 and stable operation for 50 h. This work demonstrates a viable strategy for enabling single‐electrode, bias‐free photoelectrochemical (PEC) hydrogen production through targeted band engineering and reaction replacement.