Solution‐Processed GaSe Nanoflake‐Based Films for Photoelectrochemical Water Splitting and Photoelectrochemical‐Type Photodetectors
Marilena Isabella Zappia, Gabriele Bianca, Sebastiano Bellani, Michele Serri, Leyla Najafi, Reinier Oropesa‐Nuñez, Beatriz Martín‐García, Daniel Bouša, David Sedmidubský, Vittorio Pellegrini, Zdeněk Sofer, A. Cupolillo, Francesco Bonaccorso
Abstract
Abstract Gallium selenide (GaSe) is a layered compound, which has been exploited in nonlinear optical applications and photodetectors due to its anisotropic structure and pseudodirect optical gap. Theoretical studies predict that its 2D form is a potential photocatalyst for water splitting reactions. Herein, the photoelectrochemical (PEC) characterization of GaSe nanoflakes (single‐/few‐layer flakes), produced via liquid phase exfoliation, for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in both acidic and alkaline media is reported. In 0.5 m H 2 SO 4 , the GaSe photoelectrodes display the best PEC performance, corresponding to a ratiometric power‐saved metric for HER (Φ saved,HER ) of 0.09% and a ratiometric power‐saved metric for OER (Φ saved,OER ) of 0.25%. When used as PEC‐type photodetectors, GaSe photoelectrodes show a responsivity of ≈0.16 A W −1 upon 455 nm illumination at a light intensity of 63.5 µW cm −2 and applied potential of −0.3 V versus reversible hydrogen electrode (RHE). Stability tests of GaSe photodetectors demonstrated a durable operation over tens of cathodic linear sweep voltammetry scans in 0.5 m H 2 SO 4 for HER. In contrast, degradation of photoelectrodes occurred in both alkaline and anodic operation due to the highly oxidizing environment and O 2 ‐induced (photo)oxidation effects. The results provide new insight into the PEC properties of GaSe nanoflakes for their exploitation in photoelectrocatalysis, PEC‐type photodetectors, and (bio)sensors.