Surface Engineering of Cu2O Photocathodes via Facile Graphene Oxide Decoration for Improved Photoelectrochemical Water Splitting.

Copper oxide (Cu2O) has attracted significant interest as an efficient photocathode for photoelectrochemical (PEC) water splitting owing to its abundance, suitable band gap, and band-edge potential. Nevertheless, a high charge recombination rate restricts its practical photoconversion efficiency and reduces the PEC water-splitting performance. To address this challenge, we present the facile electrodeposition of graphene oxide (GO) on the Cu2O photocathode surface. To determine the effect of varying GO weight percentages on PEC performance, varying amounts of GO were deposited on the Cu2O photocathode surface. The optimally deposited GO-Cu2O photocathode exhibited a photocurrent density of -0.39 to -1.20 mA/cm2, which was three times that of a photocathode composed of pristine Cu2O. The surface decoration of Cu2O with GO reduced charge recombination and improved the PEC water-splitting performance. These composites can be utilized in strategies designed to address the challenges associated with low-efficiency Cu2O photocathodes. The physicochemical properties of the prepared samples were comprehensively characterized by field-emission scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, Raman spectroscopy, UV-visible spectroscopy, and X-ray photoelectron spectroscopy. We believe that this research will pave the way for developing efficient Cu2O-based photocathodes for PEC water splitting.

Interface-engineered Z-scheme of BiVO4/g-C3N4 photoanode for boosted photoelectrochemical water splitting and organic contaminant elimination under solar light.

Although n-type bismuth vanadate (BiVO4) is regarded as an attractive solar-light-active photoanode, its short carrier-diffusion length, sluggish oxidation kinetics, low electronic conductivity, and high recombination rate are the major intrinsic shortcomings that limit its practical application. To this end, the rational design of a solar-light-active, metal-free BiVO4-based Z-scheme heterojunction photoanode is of great significance for achieving effective charge-separation features and maximum light utilization as well as boosting redox activity for efficient environmental treatment and photoelectrochemical water splitting. Herein, we propose a facile approach for the decoration of metal-free graphitic carbon nitride (g-C3N4) nanosheets on BiVO4 to form a Z-scheme BiVO4/g-C3N4 photoanode with boosted photoelectrochemical (PEC) water splitting and rapid photoelectrocatalytic degradation of methyl orange (MO) dye under simulated solar light. The successful preparation of the Z-scheme BiVO4/g-C3N4 photoanode was confirmed by comprehensive structural, morphological, and optical analyses. Compared with the moderate photocurrent density of bare BiVO4 (0.39 mA cm-2), the Z-scheme BiVO4/g-C3N4 photoanode yields a notable photocurrent density of 1.14 mA cm-2 at 1.23 V vs. RHE (≈3-fold higher) with the promising long-term stability of 5 h without any significant photo-corrosion. Moreover, the PEC dye-degradation studies revealed that the Z-scheme BiVO4/g-C3N4 photoanode successfully degraded MO (≈90%) in 75 min, signifying a 30% improvement over bare BiVO4. This research paves the way for rational interface engineering of solar-light-active BiVO4-based noble-metal-free Z-schemes for eco-friendly PEC water splitting and water remediation.