Atomically thin, single-crystalline InVO 4 sheets with the uniform thickness of ∼1.5 nm were convincingly synthesized, which was identified with strong, low-angle X-ray diffraction peaks. The InVO 4 atomic layer corresponding to 3 unit cells along [110] orientation exhibits highly selective and efficient photocatalytic conversion of CO 2 into CO in the presence of water vapor. Surface potential change measurement and liquid photoluminescence decay spectra confirm that the atomically ultrathin structure can shorten the transfer distance of charge carriers from the interior onto the surface and decrease the recombination in body. It thus allows more electrons to survive and accumulate on the surface, which is beneficial for activation and reduction of CO 2 . In addition, exclusively exposed {110} facet of the InVO 4 atomic layer was found to bind the generating CO weakly, facilitating quick desorption from the catalyst surface to form free CO molecules, which provides an ideal platform to catalytically selective CO product.

High-index crystal facets, denoted by a set of Miller indices {hkl} with at least one index greater than unity, possess a high density of low-coordinated atoms, steps, edges, and kinks that serve as highly active catalytic sites. [1][2][3] High-index surfaces normally grow faster than lowindex ones and are usually lost during crystal growth due to minimization of the total surface energy. Although the selective exposure of high-index facets at the surface is an important and challenging research topic, much progress has been made in the formation of many kinds of relevant noble metal nanocrystals, which have been extensively applied in catalytic reactions, including those in fuel cells, [4] photocatalysis, [5][6][7] electrocatalysis, [8,9] and petroleum catalytic reforming. [10] However, the generation of metal oxide micro-and nanocrystallites with high-index surfaces is comparatively more difficult due to the presence of strong metal-oxygen bonds and diverse crystal packing structures. [11] Only a few binary metal oxides, such as Co 3 O 4 , [12] anatase TiO 2 , [13][14][15] Fe 3 O 4 , [16] Cu 2 O, [17,18] and SnO 2 , [19] have been successfully achieved. Multinary metal oxide crystals are relatively more meaningful than binary ones because they not only possess more complex functions, but their properties also be readily adjusted by tuning the ratio of the component elements. Bismuth vanadate (BiVO 4 ) attracts intense interest as one of the most promising visible-light-active photocatalysts for water oxidation, due to its appropriate valence band edge located at ≈2.4 eV versus normal hydrogen electrode (NHE). [20] Varieties of morphological BiVO 4 , which are generally enclosed by lowindex {111}, {110}, or {100} planes, were formed through control of the synthetic methods and experimental conditions. [21][22][23] The photocatalytic behavior of BiVO 4 is highly dependent on its surface structure, in which photogenerated electrons and holes can be preferentially separated and accumulated on {010} and {110} facets, respectively, via the driving force created by the different band energies of the two facets. [24,25] Herein, we report the synthesis unprecedented 30-faceted BiVO 4 polyhedra predominantly surrounded by high-index {132}, {321}, and {121} facets. These BiVO 4 materials exhibit 3-5 time enhancements in O 2 evolution from photocatalytic water oxidation, relatively to that of low-indexed counterparts. Theory calculations reveal that the high-index surfaces are energetically favorable for water dissociation and exhibit a notable reduction in the overpotential (0.77-1.14 V) of the oxygen Unprecedented 30-faceted BiVO 4 polyhedra predominantly surrounded by {132}, {321}, and {121} high-index facets are fabricated through the engineering of high-index surfaces by a trace amount of Au nanoparticles. The growth of high-index facets results in a 3-5 fold enhancement of O 2 evolution from photocatalytic water splitting by the BiVO 4 polyhedron, relative to its low-index counterparts. Theory calculations reveal th...

Artificial photosynthesis, light-driving CO2 conversion into hydrocarbon fuels, is a promising strategy to synchronously overcome global warming and energy-supply issues. The quaternary AgInP2S6 atomic layer with the thickness of ~ 0.70 nm were successfully synthesized through facile ultrasonic exfoliation of the corresponding bulk crystal. The sulfur defect engineering on this atomic layer through a H2O2 etching treatment can excitingly change the CO2 photoreduction reaction pathway to steer dominant generation of ethene with the yield-based selectivity reaching ~73% and the electron-based selectivity as high as ~89%. Both DFT calculation and in-situ FTIR spectra demonstrate that as the introduction of S vacancies in AgInP2S6 causes the charge accumulation on the Ag atoms near the S vacancies, the exposed Ag sites can thus effectively capture the forming *CO molecules. It makes the catalyst surface enrich with key reaction intermediates to lower the C-C binding coupling barrier, which facilitates the production of ethene.

To improve the photoelectrochemical activity of WO 3 , Bi 2 S 3 /WO 3 heterojunction films were designed by coupling WO 3 films with varying amounts of urchin-like Bi 2 S 3 nanospheres. The WO 3 films were composed of WO 3 nanoprism arrays, which were synthesized using a solvothermal method. After coating a single layer of Bi 2 S 3 on top of the WO 3 film, the resulting Bi 2 S 3 /WO 3 heterojunction film showed enhanced photoelectrochemical activity. At 1.2 V vs. Ag/AgCl, the initial photocurrent density of the Bi 2 S 3 /WO 3 heterojunction film with one layer of Bi 2 S 3 was 1.33 mA cm À2 in 0.1 M Na 2 SO 4 and 1.19 mA cm À2 in a 0.2 M NaCl mixed water-ethanol solution, which was 40% and 32% higher than the bare WO 3 film under the same conditions, respectively. The optimal number of Bi 2 S 3 layers for coupling with the WO 3 film was found to be 3 layers, which had the highest photocurrent density and IPCE values. The photoelectrochemical activity of Bi 2 S 3 /WO 3 heterojunction film was not stable for water oxidation due to photocorrosion in aqueous electrolyte, but it was stable in the NaCl mixed waterethanol solution and a non-aqueous solution containing iodide/triiodide as a redox couple. The origin of enhanced photoelectrochemical activity of the Bi 2 S 3 /WO 3 heterojunction film was primarily ascribed to the band potential matching between WO 3 and Bi 2 S 3 , which is advantageous for charge separation.