# BiVO4–Cu2O/CuO Nanocubes with High Charge Injection and Charge Separation Rates for Enhanced Photoelectrochemical Water Oxidation

## TL;DR

Researchers improved water oxidation using a BiVO4–Cu2O/CuO nanocube structure, boosting charge efficiency and oxygen production.

## Contribution

A novel BiVO4–Cu2O/CuO nanocube heterojunction was developed to enhance photoelectrochemical water oxidation.

## Key findings

- The BiVO4–Cu2O/CuO nanocube increased oxygen evolution current density to 2.3 mA/cm² at 1.23 V vs RHE.
- Charge injection and separation efficiencies exceeded 60% with the nanocube structure.
- CuO nanowires showed lower charge separation efficiency compared to nanocubes.

## Abstract

Bismuth vanadate
(BiVO4) shows promise as
a photoanode
for water oxidation, with a relatively low band gap of 2.4 eV. However,
its performance is limited by poor carrier separation and surface
recombination. To address these limitations, a BiVO4–Cu2O/CuO nanocube (NC) heterojunction was successfully developed,
increasing the photogenerated oxygen evolution current density to
2.3 mA/cm2 at 1.23 V vs RHE, compared to 1.4 mA/cm2 for bare BiVO4. Addition of drop-casted Cu2O/CuO NCs on BiVO4 increases both the charge injection
efficiency and the charge separation efficiency to over 60% at 1.23
V vs RHE. In comparison, the addition of drop-casted CuO nanowires
(NWs) to BiVO4 increased the charge injection efficiency
to over 65%, but it only moderately increased the charge separation
efficiency to 49% at 1.23 V vs RHE. These results highlight the importance
of the interface between BiVO4 and the catalyst layer for
an enhanced photocurrent. In the Cu2O/CuO NCs, bulk Cu2O likely serves as a hole-extracting heterojunction, while
surface CuO likely functions as a catalyst. In contrast, the CuO NWs
function primarily as a catalyst.