Design of efficient heterojunction photoanodes with appropriate band alignment and ease of charge separation has been one of the most highly focused research areas on photoelectrodes. This work demonstrates the...

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Morphology-modulated and crystal facet-tailored electrocatalytic activity of Co3O4 nanocrystals (NCs) anchored on the reduced graphene oxide (rGO) sheet is explored for selective reduction of carbon dioxide (CO2) to C2 products. Specially engineered interconnected nanonetwork of the Co3O4 (111) facet dominated by tetrahedral Co­(II) on rGO is synthesized by tuning the cobalt to GO ratio. The structural properties of of rGO–Co3O4 composite is analyzed by high-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) techniques. Faradaic efficiencies (FE) of ethanol and ethylene attain the maximum value of 45.9 and 28.8%, respectively, at the optimum potential of −0.4 V vs RHE (FEethanol/ethylene = 1.7). The density functional theory (DFT) reveals strong dΠ–pΠ interactions between Co3O4 and graphene at interconnected morphology, which increases hybridization as well as electronic conductivity of the heterostructure compared to pristine Co3O4 (as supported by EIS and XPS analyses), causing deformation on the graphene sheet. The potential difference between the adjacent intermediates attached on tetrahedral Co­(II) and octahedral Co­(III) of (111) faceted Co3O4 NCs promote the C–C coupling and enhance the multi-electron transport through a circuit-like mechanism for the synthesis of ethanol. We explored that notable reactivity toward CO2 reduction is not solely associated with wt % of Co3O4 but also the morphological pattern of it on rGO that control the reaction intermediate (*CO) adsorption sites facilitating ethanol formation.

Design of composite semiconductor nanostructures with proper band alignment for efficient charge separation and carrier transport has been at the center of research for photoelectrochemical water splitting. This work demonstrates the deposition of a NiFe2O4 @Fe2O3 core-shell nanostructured film sensitized with CdS to form a ternary heterojunction for cascade type electron transfer. The hematite nanostructures were grown by hydrothermal approach through dipping into a solution of Nickel Nitrate yielded anchoring of Ni2+ ions on the outer surface. The films were then annealed at 650 0C for the diffusion of Ni2+ ions into the hematite lattice which forms core-shell NiFe2O4 @Fe2O3 heterojunction. The films were further sensitized with CdS nanoparticles deposited by a hydrothermal approach to form the final ternary heterojunction photoanode. Several different nanostructures were grown and the effect of crystal facet tailoring was observed on Ni loading and photoelectrochemical performance. The photoelectrochemical measurements were carried out using a potentiostat under 100 mW/cm2 light source (150W Xenon Lamp) with Pt counter electrode and 0.5 M Na2S and 0.5 M Na2SO3 electrolyte. A current density of 3.47 mA/cm2 was observed at 1.23 V (vs Ag/AgCl). An Applied Bias to Photocurrent Efficiency (ABPE) of 1.8 % photoconversion efficiency was observed using the fabricated electrodes at 0.288V (vs Ag/AgCl).