Enhanced Hydrogen Evolution under Simulated Sunlight from Neutral Electrolytes on (ZnSe)_0.85(CuIn_0.7Ga_0.3Se₂)_0.15 Photocathodes Prepared by a Bilayer Method

Abstract

A (ZnSe) (CuIn Ga Se ) photocathode with a bilayer structure was fabricated and found to exhibit a photocurrent almost twice that of a photocathode with a monolayer structure during hydrogen evolution from water. The cathodic photocurrent reached maximum values of 12 and 4.9 mA cm at 0 and 0.6 V in a neutral phosphate buffer under simulated sunlight, while the half-cell solar-to-hydrogen conversion efficiency was 3.0 % at 0.6 V , with a maximum value of 3.6 % at 0.45 V . Cross-sectional mapping of the electron-beam-induced current established that the increased photocurrent can be attributed to improved uniformity at the solid-liquid junction in the bilayer sample, which results in enhanced carrier collection.

Stable Hydrogen Production from Water on an NIR‐Responsive Photocathode under Harsh Conditions

“…These curves show that the photocurrent clearly increased after the activation process. The values of 9.1 mA cm −2 at 0 V RHE and 2.9 mA cm −2 at 0.6 V RHE obtained at pH 13 following activation are comparable to values previously reported when using Pt/Mo/Ti . The onset potential was also dependent on the pH of the electrolyte; alkaline conditions resulted in a 0.15 V increase in the onset potential.…”

“…Incident photon‐to‐current conversion efficiency (IPCE) spectra acquired at 0 and 0.6 V RHE are shown in Figure . Even though the color of RuO 2 is dark green, the IPCE at wavelengths <550 nm was as high as 60%, which is comparable to the performance of conventional photocathodes modified with Pt/Mo/Ti . This result suggests that the RuO 2 layer can function as a HER catalyst and a conductor layer just as efficiently as Pt/Mo/Ti.…”

“…Current–time curves for RuO 2 /CdS/(ZnSe) 0.85 (CIGS) 0.15 photocathodes at 0.6 V RHE under simulated sunlight are shown in Figure . The initial photocurrents at 0.6 V RHE were 0.1 and 1.2 mA cm −2 in electrolytes at pH 7 and 13, respectively, both of which are relatively low compared with the performance of a material modified with Pt as an HER catalyst and a binary Mo/Ti combination as a conductor layer (Pt/Mo/Ti) . However, the photocurrents gradually increased to 0.3 and 2.9 mA cm −2 (at pH 7 and 13) over the span of several hours, and the corresponding half‐cell STH (HC‐STH), which indicates the energy conversion efficiency of a photoelectrode under application of bias voltage in a three‐electrode system, reached 1.7% in the case of pH 13.…”

“…In a demonstration using an actual PEC cell composed of a (ZnSe) 0.85 (CuIn 0.7 Ga 0.3 Se 2 ) 0.15 (abbreviated as (ZnSe) 0.85 (CIGS) 0.15 herein)‐based photocathode and a BiVO 4 ‐based photoanode, an obvious decrease in the photocurrent due to the corrosion of the surface modifiers on the photocathode was observed . (ZnSe) 0.85 (CIGS) 0.15 ‐based photocathodes exhibit a long absorption edge of ≈900 nm, an outstanding onset potential of 0.9 V RHE and a relatively large photocurrent of 12 mA cm −2 (attributed to the HER) under simulated sunlight in neutral electrolytes, and thus appear suitable for overall water splitting without an external bias voltage . However, the STH of such PEC cells will decay over a span of several hours, and so the durability of these units is insufficient.…”

A Low‐Cost NiO Hole Transfer Layer for Ohmic Back Contact to Cu2O for Photoelectrochemical Water Splitting

“…Solar energy conversion is an attractive and sustainable solution to the energy crisis and environmental pollution . Photoelectrochemical (PEC) water splitting is a feasible way to convert solar energy into hydrogen fuel with high specific enthalpy and clean combustion product . Recent years, many researches have focused on the investigation of efficient PEC devices .…”