ZnSe Nanorods as Visible‐Light Absorbers for Photocatalytic and Photoelectrochemical H₂ Evolution in Water

Abstract

A precious‐metal‐ and Cd‐free photocatalyst system for efficient H 2 evolution from aqueous protons with a performance comparable to Cd‐based quantum dots is presented. Rod‐shaped ZnSe nanocrystals (nanorods, NRs) with a Ni(BF 4 ) 2 co‐catalyst suspended in aqueous ascorbic acid evolve H 2 with an activity up to 54±2 mmol g ZnSe −1 h −1 and a quantum yield of 50±4 % ( λ =400 nm) under visible light illumination (AM 1.5G, 100 mW cm −2 , λ >400 nm). Under simulated full‐spectrum solar irradiation (AM 1.5G, 100 mW cm −2 ), up to 149±22 mmol g ZnSe −1 h −1 is generated. Significant photocorrosion was not noticeable within 40 h and activity was even observed without an added co‐catalyst. The ZnSe NRs can also be used to construct an inexpensive delafossite CuCrO 2 photocathode, which does not rely on a sacrificial electron donor. Immobilized ZnSe NRs on CuCrO 2 generate photocurrents of around −10 μA cm −2 in an aqueous electrolyte solution (pH 5.5) with a photocurrent onset potential of approximately +0.75 V vs. RHE. This work establishes ZnSe as a state‐of‐the‐art light absorber for photocatalytic and photoelectrochemical H 2 generation.

Nonepitaxial Gold‐Tipped ZnSe Hybrid Nanorods for Efficient Photocatalytic Hydrogen Production

“…These merits make them potential supplements or alternatives to the Cd‐based materials in photocatalytic hydrogen generation and biomedical applications . Recent research on ZnSe and alloyed ZnS x Se 1− x NRs indicated that these Cd‐free NRs can be adopted as efficient photocatalysts for efficient hydrogen generation and oxygen evolution reactions …”

Recent Advances in Zinc‐Containing Colloidal Semiconductor Nanocrystals for Optoelectronic and Energy Conversion Applications

“…demonstrated that ZnSSe alloyed nanorods showed increased oxygen evolution reaction (OER) activity compared with pure ZnSe and ZnS nanorods (Figure a) because the alloyed nanorods have reduced energy barrier for oxygen evolution . Following from this work, ZnSe nanorods was applied as the visible light range absorbers for H 2 evolution with performances exceeding those of Cd‐containing QDs …”

Synthesis of Anisotropic ZnSe Nanorods with Zinc Blende Crystal Structure

“…Previously reported ZnSe NRs all had the hexagonal WZ crystal structure, with the initially formed ZnSe clusters being able to attach along their c axes or to individually grow along the c axis to form 1D ZnSe NCs . Herein, we have obtained ZnSe NRs with the ZB crystal structure for the first time, and thus we conducted further experiments in an effort to understand their formation mechanism.…”

“…Some examples of ZnSe NRs have been reported previously, but in far less an extent than for the Cd‐based NRs. Most of the synthetic routes to form ZnSe NRs used the oriented attachment method, wherein small non‐anisotropic ZnSe clusters attached to each other to form ZnSe NRs with or without the use of confining or directing organic templates . To the best of our knowledge, all of the reported ZnSe NRs produced by this or other methods exhibited the hexagonal wurtzite (WZ) crystal structure, even when their synthesis started from ZnSe clusters with a cubic zinc blende (ZB) crystal structure .…”

“…Owing to the quantum confinement effect, the band gap of ZnSe NCs increases, moving to the ultraviolet (UV)–blue spectral range, while the doping of those may extend it into the visible region . Some examples of ZnSe NRs have been reported previously, but in far less an extent than for the Cd‐based NRs. Most of the synthetic routes to form ZnSe NRs used the oriented attachment method, wherein small non‐anisotropic ZnSe clusters attached to each other to form ZnSe NRs with or without the use of confining or directing organic templates .…”