Fabrication of TiOx/Sb2Se3/p-NiOx photocathode for efficient photoelectrochemical water reduction

Abstract

Photoelectrochemical (PEC) water splitting directly converts solar energy into clean and sustainable hydrogen energy, representing a promising and effective technique for solving the world's energy crisis. A hole transfer layer (HTL) plays a vital role for extracting holes from a semiconductor layer to a back electrode in PEC cells for water splitting. In this work, a TiOx/Sb2Se3/NiOx photocathode was fabricated by using p-NiOx as HTL. We show that the electrical properties of NiOx films can be well adjusted by the pulsed laser deposition technique. By systematically adjusting the electrical properties of the NiOx HTL and passivating the surface defects through coating with the TiOx layer, we achieved a high photocurrent density of up to −18.08 mA cm−2 at 0 V vs a reversible hydrogen electrode (RHE), an onset potential of 0.43 V vs RHE, and a half-cell solar to hydrogen conversion efficiency of 1.01% for the TiOx/Sb2Se3/NiOx photocathode. This work demonstrated NiOx as a potential hole transport material for a cost-effective Sb2Se3 PEC cell.

Fabrication of a Sb2Se3/CuSbS2 Heterojunction Photocathode for Photoelectrochemical Water Splitting

“…In addition, the work function of Mo is close to the conduction band minimum (CBM) of Sb 2 Se 3 , which makes it easy to form the recombination center . Meanwhile, Lee et al reported that Cu-doped NiO x as a hole-selective layer for Sb 2 Se 3 obtained a photocurrent density of 17.5 mA cm –2 at 0 V RHE , and the preparation of NiO x by pulsed laser deposition as the hole transport layer (HTL) of the Sb 2 Se 3 photocathode has been reported by our group, but the low conductivity of nickel oxide is not favorable for the hole transfer …”

“…19 Meanwhile, Lee et al reported that Cu-doped NiO x as a holeselective layer for Sb 2 Se 3 obtained a photocurrent density of 17.5 mA cm −2 at 0 V RHE , 18 and the preparation of NiO x by pulsed laser deposition as the hole transport layer (HTL) of the Sb 2 Se 3 photocathode has been reported by our group, but the low conductivity of nickel oxide is not favorable for the hole transfer. 20 As a p-type semiconductor, copper antimony sulfide (CuSbS 2 ) is an emerging material for PEC cells because of its suitable band gap and high optical absorption coefficent. 21 Furthermore, it is made of low-cost, low-toxicity, and Earthabundant elements.…”

Hole Transport Layer in Photoelectrochemical Water Splitting

“…[63] The second type of the photocathode hole transport system (Figure 5b) mainly consists of a conductive substrate, a HTL, a photocatalyst, and a hydrogen evolution cocatalyst. [73][74][75][76][77][78][79][80][81] For an unstable photocatalytic systems, a protective layer is often added between the photocatalyst and the cocatalyst. [73,76,77] Furthermore, most of the cocatalysts in this system are platinum, which not only provides surface redox sites and increases hydrogen production, but also collects electrons and promotes carrier transport.…”

“…[73][74][75][76][77][78][79][80][81] For an unstable photocatalytic systems, a protective layer is often added between the photocatalyst and the cocatalyst. [73,76,77] Furthermore, most of the cocatalysts in this system are platinum, which not only provides surface redox sites and increases hydrogen production, but also collects electrons and promotes carrier transport. [73,74,[76][77][78] Under illumination, the photogenerated holes are transferred from the VB of photocatalyst to the counter electrode through the conductive glass and external circuit for water oxidation.…”

“…[73,76,77] Furthermore, most of the cocatalysts in this system are platinum, which not only provides surface redox sites and increases hydrogen production, but also collects electrons and promotes carrier transport. [73,74,[76][77][78] Under illumination, the photogenerated holes are transferred from the VB of photocatalyst to the counter electrode through the conductive glass and external circuit for water oxidation. Photogenerated electrons are transferred from the CB of the photocatalyst to the interface of the cocatalyst/electrolyte for hydrogen evolution.…”