High Efficiency Si Photocathode Protected by Multifunctional GaN Nanostructures

Abstract

Photoelectrochemical water splitting is a clean and environmentally friendly method for solar hydrogen generation. Its practical application, however, has been limited by the poor stability of semiconductor photoelectrodes. In this work, we demonstrate the use of GaN nanostructures as a multifunctional protection layer for an otherwise unstable, low-performance photocathode. The direct integration of GaN nanostructures on n-p Si wafer not only protects Si surface from corrosion but also significantly reduces the charge carrier transfer resistance at the semiconductor/liquid junction, leading to long-term stability (>100 h) at a large current density (>35 mA/cm) under 1 sun illumination. The measured applied bias photon-to-current efficiency of 10.5% is among the highest values ever reported for a Si photocathode. Given that both Si and GaN are already widely produced in industry, our studies offer a viable path for achieving high-efficiency and highly stable semiconductor photoelectrodes for solar water splitting with proven manufacturability and scalability.

A Single-Junction Cathodic Approach for Stable Unassisted Solar Water Splitting

“…With the use of plasma-assisted epitaxy, the surface of such nanostructures can be engineered to be N rich, which can protect against photo-corrosion and oxidation in harsh photocatalytic reaction. 33,34 Here, we have demonstrated that an In 0.25 Ga 0.75 N nanowire photocathode grown directly on Si wafer can exhibit relatively efficient and stable unassisted solar water splitting. At zero bias versus Pt counter electrode, an InGaN nanowire photocathode can exhibit an STH efficiency of 3.4%, which, to the best of our knowledge, is the highest efficiency value ever achieved in a single-photon system for unbiased photoelectrochemical water splitting.…”

“…For the three-electrode configuration, an additional Ag/AgCl reference electrode was used (in saturated KCl, E (vs. RHE) = +0.197 V + E (vs. Ag/AgCl) + 0.059 3 pH at 25 C). 34 Structural and Optical Characterization Photoluminescence spectroscopy of InGaN nanowires was performed using a He-Cd 325 nm excitation laser. SEM images were taken with a secondary electron (SE) detector using a Hitachi SU8000 system (5 kV), Tescan MIRA3 system (15 kV), and a JEOL IT500 SEM (10 kV) with an EDX detector.…”

Nanostructured core–shell metal borides–oxides as highly efficient electrocatalysts for photoelectrochemical water oxidation

“…4,5 To date, significant improvement has been achieved for photocathodes; profiting highly from the experiences in industrial semiconductor production technology such as solar cell development. 6,7 Nevertheless, water oxidation involving the transfer of four electrons is demanding with respect to kinetics and stability, thus limiting the PEC watersplitting efficiency. 8,9 Consequently, it is crucial to develop highly active, stable and low-cost photoanodes to achieve commercialization of PEC technology in the future.…”

Ion Beam Defect Engineering on ReS2/Si Photocathode with Significantly Enhanced Hydrogen Evolution Reaction

“…It has been almost four decades of pursuits in the solar‐driven photoelectrochemical (PEC) water splitting for efficient hydrogen (H 2 ) production, as a clean fuel without direct production of CO 2 . 2D transition metal dichalcogenides (TMDs), such as MoS 2 , MoSe 2 , and so forth, are always loaded on surface of p‐type doped silicon (p‐Si) photocathode for hydrogen evolution reaction (HER). Generally, the TMDs/Si composite photoelectrodes have advantages of large specific surface areas, low material costs, and highly catalytic activities.…”