Synergy Effect of the Enhanced Local Electric Field and Built-In Electric Field of CoS/Mo-Doped BiVO₄ for Photoelectrochemical Water Oxidation

Abstract

Bismuth vanadate is a promising material for photoelectrochemical water oxidation. However, it suffers from a low quantum efficiency, poor stability, and slow water oxidation kinetics. Here, we developed a novel photoanode of CoS/Mo-BiVO 4 with excellent photoelectrochemical water oxidation performance. It achieved a photocurrent density of 4.5 mA cm −2 at 1.23 V versus the reversible hydrogen electrode, ∼4 times that of BiVO 4 . The CoS/Mo-BiVO 4 photoanode also exhibited good stability, and the photocurrent density generated by the CoS/Mo-BiVO 4 photoanode did not significantly decrease after light irradiation for 2 h. Upon replacement of part of the V with Mo doping in BiVO 4 , the local electric field around the Mo−O bond was enhanced, thus promoting carrier separation in BiVO 4 . The CoS was deposited on the surface of Mo-BiVO 4 , forming a built-in electric field at the interface. Under the action of the bias electric field and the built-in electric field, the carriers of CoS/Mo-BiVO 4 were efficiently separated in the direction of the inverse type II heterojunction. In addition, CoS improved the light absorption and charge injection efficiency of the CoS/Mo-BiVO 4 photoanode.

Study on defects during Fe3+ doping and annealing in ADP crystals

“…This suggests that Fe 3+ doping at lower concentrations has a limited impact on the ADP crystal structure, primarily introducing slight lattice distortions without significantly changing the grain size. In contrast, the annealed samples (TA series) exhibited more significant changes in lattice parameters and volumes, especially at higher doping concentrations (TA 3 ), where the c-axis noticeably decreased to 7.335 Å, and the unit cell volume reduced to approximately 409 Å 3 . This indicates that the annealing process may facilitate the reorganization of internal defects and rearrangement of the lattice, leading to lattice compression and a reduction in grain size.…”

“…In ADP crystals, both Fe 3+ doping and annealing treatments significantly impacted the lattice parameters and unit cell volumes, reflecting changes in grain size and lattice strain. In undoped samples, as the concentration of Fe 3+ doping increased from 10 CrystEngComm Paper ppm to 30 ppm, the lattice parameter a remained relatively unchanged, while c fluctuated slightly, with the unit cell volume oscillating around 425 Å 3 . This suggests that Fe 3+ doping at lower concentrations has a limited impact on the ADP crystal structure, primarily introducing slight lattice distortions without significantly changing the grain size.…”

“…Inorganic crystals such as potassium dihydrogen phosphate (KH 2 PO 4 , KDP), ammonium dihydrogen phosphate (NH 4 H 2 PO 4 , ADP), and barium borate (BaB 2 O 4 , BBO) are extensively applied in the fields of frequency converters, monochromators, optoelectronic switches, and optical storage devices due to their outstanding nonlinear optical properties. [1][2][3][4] In high-power laser systems, KDP is currently the only nonlinear optical crystal in practical use. 5 ADP crystals, which share a similar structure with KDP, exhibit superior optical uniformity, enhanced SHG coefficients, improved thermal stability, and higher laserinduced damage thresholds (LIDTs).…”

Rational Design of CoOOH/α-Fe2O3/SnO2 for Boosted Photoelectrochemical Water Oxidation: The Roles of Underneath SnO2 and Surface CoOOH

“…However, PEC water splitting device still suffers from the sluggish oxygen evolution reaction (OER) kinetics over the photoanode . To date, many semiconductor metal oxides/oxynitrides, such as TiO 2 , BiVO 4 , WO 3 , α-Fe 2 O 3 , and AB­(O,N) 3 (A = Ba, Ca, and Sr; B = Ta and Nb) have been developed to optimize PEC capacity for the OER. − Among them, α-Fe 2 O 3 is considered to be a promising candidate with suitable band gap (∼2.1 eV), elemental abundance, and chemical stability in alkaline solution . Nevertheless, the PEC OER activity of α-Fe 2 O 3 is still limited by several intrinsic defects, like poor conductivity, short minority carrier lifetime, and poor surface OER kinetics .…”