Enhanced Photoelectrochemical Water Splitting by Surface Modified Electrodeposited n‐Cu₂O Thin Films

Abstract

A surface modification technique is developed for electrodeposited n‐cuprous oxide (Cu2O) thin film electrodes to enhance water splitting in a photoelectrochemical (PEC) cell. For this, Cu2O films are modified using ammonium sulfide vapor with a unique exposure condition to produce ultrathin sulfided surface layers. To ascertain the effect of surface modification, films are investigated in a PEC cell containing 0.1 m sodium acetate aqueous electrolyte using current–voltage, spectral response, and capacitance–voltage measurements. It is revealed that as a result of the surface modification, high photocurrents are produced by the surface‐modified electrodes. Also, it is revealed that the Fermi level pinning presents at the Cu2O/electrolyte interface can be removed and the flat band potential can be shifted negatively by the surface modification. The experimental evidences support the idea that the surface modification can change the surface states present at the n‐Cu2O/electrolyte interface. The enhancement of photocurrent may be attributed to the increase in depletion layer thickness and reduction of surface recombination of photogenerated charge carriers. The surface modification technique developed in this study for n‐Cu2O films enables to produce an enhanced solar‐to‐hydrogen conversion efficiency of 1.47% at the bias potential of 0.553 V versus reversible hydrogen electrode.

Nanoscale electrodeposition: Dimension control and 3D conformality

“…[ 125–128 ] Semiconductor films like Fe 2 O 3 , TiO 2 , BiVO 4, and Cu 2 O are widely utilized in photoelectrochemical (PEC) water splitting electrodes due to their high light‐harvesting ability. [ 129–136 ] Facile control of thickness and morphology through the electrodeposition method can effectively adjust the dynamics of film appropriate for boosting PEC performance. For instance, Lee et al.…”

“…[125][126][127][128] Semiconductor films like Fe 2 O 3 , TiO 2 , BiVO 4, and Cu 2 O are widely utilized in photoelectrochemical (PEC) water splitting electrodes due to their high light-harvesting ability. [129][130][131][132][133][134][135][136] Facile control of thickness and morphology through the electrodeposition method can effectively adjust the dynamics of film appro-priate for boosting PEC performance. For instance, Lee et al reported the effect of electrodeposited NiO x /Ni nanoparticles coverage and crystallinity on the PEC characteristics of NiO x /Ni/n-Si photoanodes.…”

Photocorrosion of n‐ and p‐Type Semiconducting Oxide‐Covered Metals: Case Studies of Anodized Titanium and Copper

“…Titanium and copper were studied here; TiO 2 is a prototypical n‐type oxide, whereas Cu 2 O is one of the few p‐type oxides that forms spontaneously on metals. [ 1 ] However, Cu 2 O formed in the presence of chloride, [ 34,35 ] very thin films in chloride‐free NaOH, [ 36 ] or electrodeposited films [ 37 ] may also become n‐type. Experimentally, anodizing was used to grow oxides anatase TiO 2 and cuprite Cu 2 O with different thickness based on literature procedures (see Supporting Information).…”

“…Titanium and copper were studied here; TiO 2 is a prototypical n-type oxide, whereas Cu 2 O is one of the few p-type oxides that forms spontaneously on metals. [1] However, Cu 2 O formed in the presence of chloride, [34,35] very thin films in chloride-free NaOH, [36] or electrodeposited films [37] may also become n-type.…”

Photoelectrochemical Immunosensor Based on a 1D Fe2O3/3D Cd-ZnIn2.2Sy Heterostructure as a Sensing Platform for Ultrasensitive Detection of Neuron-Specific Enolase

“…In addition, it offers excellent advantages of diverse morphology, high natural abundance, and a suitable bandgap of 2.2 eV. , However, the photocurrent response of most semiconductors is weaker than that of compound semiconductor materials. Many strategies have been developed to improve the photocurrent response of PEC immunosensors, such as surface modification, surface passivation, morphology control, formation of heterojunction structures, , and metal doping . Among them, heterojunction and metal doping are the foci of semiconductor modification.…”