Electrochemical production of hydrogen peroxide (H2O2) from water oxidation could provide a very attractive route to locally produce a chemically valuable product from an abundant resource. Herein using density functional theory calculations, we predict trends in activity for water oxidation towards H2O2 evolution on four different metal oxides, i.e., WO3, SnO2, TiO2 and BiVO4. The density functional theory predicted trend for H2O2 evolution is further confirmed by our experimental measurements. Moreover, we identify that BiVO4 has the best H2O2 generation amount of those oxides and can achieve a Faraday efficiency of about 98% for H2O2 production.

Tungsten trioxide/bismuth vanadate heterojunction is one of the best pairs for solar water splitting, but its photocurrent densities are insufficient. Here we investigate the advantages of using helical nanostructures in photoelectrochemical solar water splitting. A helical tungsten trioxide array is fabricated on a fluorine-doped tin oxide substrate, followed by subsequent coating with bismuth vanadate/catalyst. A maximum photocurrent density of B5.35±0.15 mA cm À 2 is achieved at 1.23 V versus the reversible hydrogen electrode, and related hydrogen and oxygen evolution is also observed from this heterojunction. Theoretical simulations and analyses are performed to verify the advantages of this helical structure. The combination of effective light scattering, improved charge separation and transportation, and an enlarged contact surface area with electrolytes due to the use of the bismuth vanadatedecorated tungsten trioxide helical nanostructures leads to the highest reported photocurrent density to date at 1.23 V versus the reversible hydrogen electrode, to the best of our knowledge.

As the development of oxygen evolution co-catalysts (OECs) is being actively undertaken, the tailored integration of those OECs with photoanodes is expected to be a plausible avenue for achieving highly efficient solar-assisted water splitting. Here, we demonstrate that a black phosphorene (BP) layer, inserted between the OEC and BiVO 4 can improve the photoelectrochemical performance of pre-optimized OEC/BiVO 4 (OEC: NiOOH, MnO x, and CoOOH) systems by 1.2∼1.6-fold, while the OEC overlayer, in turn, can suppress BP self-oxidation to achieve a high durability. A photocurrent density of 4.48 mA·cm −2 at 1.23 V vs reversible hydrogen electrode (RHE) is achieved by the NiOOH/BP/BiVO 4 photoanode. It is found that the intrinsic p -type BP can boost hole extraction from BiVO 4 and prolong holes trapping lifetime on BiVO 4 surface. This work sheds light on the design of BP-based devices for application in solar to fuel conversion, and also suggests a promising nexus between semiconductor and electrocatalyst.

 Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

No abstract

The two-electron water oxidation reaction (2e-WOR) is a promising route for distributed electrochemical synthesis of hydrogen peroxide (H 2 O 2 ), an effective and green oxidizer, bleaching agent, and antiseptic. To date, the best electrocatalyst for 2e-WOR, in terms of selectivity against the competing 4e-WOR to form O 2 , is BiVO 4 . Nevertheless, BiVO 4 is unstable and has a high overpotential of ∼340 mV at 0.2 mA/cm 2 for 2e-WOR. Herein, we use density functional theory to identify a new, efficient, selective, and stable electrocatalyst for 2e-WOR, i.e., the ternary oxide calcium stannate (CaSnO 3 ). Our experiments show that CaSnO 3 achieves an overpotential of 230 mV at 0.2 mA/cm 2 , peak Faraday efficiency of 76% for 2e-WOR at 3.2 V vs the reversible hydrogen electrode (RHE), and stable performance for over 12 h, outperforming BiVO 4 in all aspects. This work demonstrates the promise of CaSnO 3 as a selective and cost-effective electrocatalyst candidate for H 2 O 2 production from water oxidation.

Photoelectrochemical oxidation of water presents a pathway for sustainable production of hydrogen peroxide (H2O2). Two-electron water oxidation toward H2O2, however, competes with the popular four-electron process to form oxygen and one-electron water oxidation to form OH radical. To date, bismuth vanadate (BiVO4) has been shown to exhibit promising selectivity toward H2O2, especially under illumination, but it suffers from high overpotential and notoriously poor stability. Herein, using density functional theory calculations, we predict that doping BiVO4 with optimal concentrations of gadolinium (Gd) not only enhances its activity for H2O2 production but also improves its stability. Experimentally, we demonstrate that intermediate amounts of Gd doping (6–12%) reduce the onset potential of BiVO4 for H2O2 production by ∼110 mV while achieving a Faradaic efficiency of ∼99.5% under illumination and prolonging the catalytic lifetime by more than a factor of 20 at 2.0 V vs RHE under illumination.

No abstract