Two Pt single-atom catalysts (SACs) of Pt-GDY1 and Pt-GDY2 were prepared on graphdiyne (GDY)supports. The isolated Pt atoms are dispersed on GDY through the coordination interactions between Pt atoms and alkynyl C atoms in GDY, with the formation of five-coordinated C -Pt-Cl species in Pt-GDY1 and four-coordinated C -Pt-Cl species in Pt-GDY2. Pt-GDY2 shows exceptionally high catalytic activity for the hydrogen evolution reaction (HER), with a mass activity up to 3.3 and 26.9 times more active than Pt-GDY1 and the state-of-the-art commercial Pt/C catalysts, respectively. Pt-GDY2 possesses higher total unoccupied density of states of Pt 5d orbital and close to zero value of Gibbs free energy of the hydrogen adsorption (|ΔGPtH* |) at the Pt active sites, which are responsible for its excellent catalytic performance. This work can help better understand the structure-catalytic activity relationship in Pt SACs.

Industrial application of overall water splitting requires developing readily available, highly efficient, and stable oxygen evolution electrocatalysts that can efficiently drive large current density. This study reports a facile and practical method to fabricate a non‐noble metal catalyst by directly growing a Co‐Fe Prussian blue analogue on a 3D porous conductive substrate, which is further phosphorized into a bifunctional Fe‐doped CoP (Fe‐CoP) electrocatalyst. The Fe‐CoP/NF (nickel foam) catalyst shows efficient electrocatalytic activity for oxygen evolution reaction, requiring low overpotentials of 190, 295, and 428 mV to achieve 10, 500, and 1000 mA cm−2 current densities in 1.0 m KOH solution. In addition, the Fe‐CoP/NF can also function as a highly active electrocatalyst for hydrogen evolution reaction with a low overpotential of 78 mV at 10 mA cm−2 current density in alkaline solution. Thus, the Fe‐CoP/NF electrode with meso/macropores can act as both an anode and a cathode to fabricate an electrolyzer for overall water splitting, only requiring a cell voltage of 1.49 V to afford a 10 mA cm−2 current density with remarkable stability. This performance appears to be among the best reported values and is much better than that of the IrO2‐Pt/C‐based electrolyzer.

The design and synthesis of efficient metal‐free photoelectrocatalysts for water splitting are of great significance, as nonmetal elements are generally earth abundant and environment friendly. As a typical metal‐free semiconductor, g‐C3N4 has received much attention in the field of photocatalytic water splitting. However, the poor photoinduced hole mobility of g‐C3N4 restrains its catalytic performance. Herein, for the first time, graphdiyne (GDY) is used to interact with g‐C3N4 to construct a metal‐free 2D/2D heterojunction of g‐C3N4/GDY as an efficient photoelectrocatalyst for water splitting. The g‐C3N4/GDY photocathode exhibits enhanced photocarriers separation due to excellent hole transfer nature of graphdiyne and the structure of 2D/2D heterojunction of g‐C3N4/GDY, realizing a sevenfold increase in electron life time (610 μs) compared to that of g‐C3N4 (88 μs), and a threefold increase in photocurrent density (−98 μA cm−2) compared to that of g‐C3N4 photocathode (−32 μA cm−2) at a potential of 0 V versus normal hydrogen electrode (NHE) in neutral aqueous solution. The photoelectrocatalytic performance can be further improved by fabricating Pt@g‐C3N4/GDY, which displays an photocurrent of −133 μA cm−2 at a potential of 0 V versus NHE in neutral aqueous solution. This work provides a new strategy for the design of efficient metal‐free photoelectrocatalysts for water splitting.

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TwoP ts ingle-atom catalysts (SACs) of Pt-GDY1 and Pt-GDY2 were prepared on graphdiyne (GDY)supports. The isolated Pt atoms are dispersed on GDYt hrough the coordination interactions between Pt atoms and alkynyl C atoms in GDY, with the formation of five-coordinated C 1 -Pt-Cl 4 species in Pt-GDY1 and four-coordinated C 2 -Pt-Cl 2 species in Pt-GDY2. Pt-GDY2 shows exceptionally high catalytic activity for the hydrogen evolution reaction (HER), with am ass activity up to 3.3 and 26.9 times more active than Pt-GDY1 and the state-of-the-art commercial Pt/C catalysts, respectively.P t-GDY2 possesses higher total unoccupied density of states of Pt 5d orbital and close to zero value of Gibbsfree energy of the hydrogen adsorption (j DG Pt H* j)atthe Pt active sites,w hich are responsible for its excellent catalytic performance.T his work can help better understand the structure-catalytic activity relationship in Pt SACs.

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Metal-halide perovskite nanocrystals have emerged as one of the promising photocatalysts in the photocatalysis field owing to their low-cost and excellent optoelectronic properties. However, this type of nanocrystals generally displays low activity in photocatalytic CO 2 reduction owing to the lack of intrinsic catalytic sites and insufficient charge separation. Herein, we functionalized CsPbBr 3 nanocrystals with graphitic carbon nitride, containing titanium-oxide species (TiO-CN) to develop an efficient composite catalyst system for photocatalytic CO 2 reduction using water as the electron source.Compared to its congener with pristine CsPbBr 3 , the introduction of TiO-CN could not only increase the number of active sites, but also led to a swift interfacial charge separation between CsPbBr 3 and TiO-CN due to their favorable energy-offsets and strong chemical bonding behaviors, which endowed this composite system with an obviously enhanced photocatalytic activity in the reduction of CO 2 to CO with water as the sacrificial reductant. Over 3-fold and 6-fold higher activities than those of pristine CsPbBr 3 nanocrystals and TiO-CN nanosheets, respectively, were observed under visible light irradiation.Our study provides an effective strategy for improving the photocatalytic activity of metal-halide perovskite nanocrystals, thus promoting their photocatalytic application in the field of artificial photosynthesis. Fig. 4 (a) Photoluminescence spectra of CsPbBr 3 and CsPbBr 3 @TiO-CN. (b) Time-resolved photoluminescence decays of CsPbBr 3 and CsPbBr 3 @TiO-CN. The gray curves are the fitting lines based on a multi-exponential function.This journal is Chem. Rev., 2019, 119, 3962-4179. Fig. 5 (a) The yields of CO generated from the photocatalytic CO 2 reduction reactions with TiO-CN, CsPbBr 3 , CsPbBr 3 @g-C 3 N 4 and CsPbBr 3 @TiO-CN photocatalysts after 10 h of irradiation under a 300 W Xe-lamp with the light intensity of 100 mW cm À2 . Gas chromatograms and mass spectra (GC-MS) of the solar-driven (b) reduction of 13 CO 2 to 13 CO (m/z ¼ 29) and (c) oxidation of H 2 18 O to 18 O 2 (m/z ¼ 36) using CsPbBr 3 @TiO-CN as the photocatalyst.34346 | RSC Adv., 2019,9,[34342][34343][34344][34345][34346][34347][34348] This journal is

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