Plasma Ag-loaded bandgap variational Zn1-xMgxO-enhanced charge separation for photoelectrochemical water oxidation of CuWO4 photoanodes

The recombination of photogenerated carriers and sluggish surface oxidation kinetics severely inhibited the development of copper tungstate (CuWO4) photoanode photoelectrochemical (PEC) water oxidation. Herein, the Zn1-xMgxO-modified CuWO4 photoanode ameliorated the vital matter of easy recombination of electron-hole pairs, where the transformation of the heterojunction type (type I to type II) between Zn1-xMgxO and CuWO4 played a crucial role in the extraction of carriers. Further, the effective charge separation was obtained utilizing the local surface plasmon resonance (LSPR) of plasma metal (Ag), which facilitated the PEC water oxidation reaction. Besides, the surface states trapped/stored holes and reduced charge transfer resistance, thus facilitating charge transfer. The overlap of the fillable surface states with filled redox coupled states ensured the enhancement of the water oxidation kinetics, which further promoted the charge transfer. As a result, the optimized CuWO4/Zn0.7Mg0.3O/Ag photoanode showed significant advancement in photocurrent density (1.71 mA/cm2 at 1.23 V vs. RHE), electrochemical impedance and stability. This work emphasized the interfacial structure modulation of two strategies that potentially provide more ideas and options for the design of other efficient photoanodes.