Inspired by natural photosynthesis, constructing inorganic/organic heterojunctions is regarded as an effective strategy to design high‐efficiency photocatalysts. Herein, a step (S)‐scheme heterojunction photocatalyst is prepared by in situ growth of an inorganic semiconductor firmly on an organic semiconductor. A new pyrene‐based conjugated polymer, pyrene‐alt‐triphenylamine (PT), is synthesized via the typical Suzuki–Miyaura reactions, and then employed as a substrate to anchor CdS nanocrystals. The optimized CdS/PT composite, coupling 2 wt% PT with CdS, exhibits a robust H2 evolution rate of 9.28 mmol h−1 g−1 with continuous release of H2 bubbles, as well as a high apparent quantum efficiency of 24.3%, which is ≈8 times that of pure CdS. The S‐scheme charge transfer mechanism between PT and CdS, is systematically demonstrated by photoirradiated Kelvin probe measurement and in situ irradiated X‐ray photoelectron spectroscopy analyses. This work provides a protocol for preparing specific S‐scheme heterojunction photocatalysts on the basis of inorganic/organic coupling.

Water oxidation is the key process for many sustainable energy technologies containing artificial photosynthesis and metal-air batteries. Engineering inexpensive yet active electrocatalysts for water oxidation is mandatory for the cost-effective generation of solar fuels. Herein, we propose a novel hierarchical porous Ni-Co-mixed metal sulfide (denoted as NiCoS) on TiCT MXene via a metal-organic framework (MOF)-based approach. Benefiting from the unique structure and strong interfacial interaction between NiCoS and TiCT sheets, the hybrid guarantees an enhanced active surface area with prominent charge-transfer conductivity and thus a superior activity toward oxygen evolution reactions (OERs). Impressively, the hierarchical NiCoS in the hybrid is converted to nickel/cobalt oxyhydroxide-NiCoS assembly (denoted as NiCoOOH-NiCoS) by OER measurement, where NiCoOOH on the surface is confirmed as the intrinsic active species for the consequent water oxidation. The hybrid material is further applied to an air cathode for a rechargeable zinc-air battery, which exhibits low charging/discharging overpotential and long-term stability. Our work underscores the tuned structure and electrocatalytic OER performance of MOF derivatives by the versatility of MXenes and provides insight into the structure-activity relationship for noble metal-free catalysts.

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continually intensified and could be out of control. Therefore, it is urgent to greatly reduce the gigantic consumption of carbonbased fossil fuels, [1,2] which emit substantial greenhouse gases and tremendously aggravate global warming. Furthermore, it is of great significance to realize carbon neutrality in human society via replacing fossil fuels with low-carbon/carbon-free alternatives. Thus, the conversion of renewable solar energy [3][4][5] into clean and carbonfree hydrogen (H 2 ) fuel is highly attractive. Such a solar-to-H 2 (STH) conversion can be achieved utilizing photocatalytic H 2 evolution via water splitting, [6][7][8][9][10] which is regarded as an alluring, environmentally benign and low-cost strategy. Hence, a highly active, robust, and affordable photocatalyst is the most sought after. [11][12][13] The rational design and synthesis of such a photocatalyst require not only the emerging nanosized building blocks with desired features, but also efficient charge dissociation/ transfer boosted by the strong built-in electric field in a favorable junction system.In the past decades, 2D materials have demonstrated great capacity to achieve efficient and cost-effective photocatalysis for various reactions, due to their distinct physicochemical features. [14][15][16][17][18][19][20][21] Recently, an emerging 2D material, FePS 3 (FPS), [22][23][24][25][26][27] has displayed numerous attractive characteristics for catalysis: i) Ultrathin structure facilitating rapid bulkto-surface electron-hole transport; ii) high specific surface area accelerating efficient adsorption/desorption of reactant and product, and benefiting the anchoring of other nanobuilding blocks; iii) exposed under-coordinated edge atoms serving as active sites to advance the reactions; iv) thicknessdependent electronic band structure promoting the regulation of light absorption and redox abilities of charge carriers; v) p-type semiconductor nature favoring the construction of certain junction system with a strong built-in electric field. Albeit the above alluring advantages, [28][29][30] only a few works reported the application of FPS in photocatalysis. For instance, FPS quantum sheets show the photocatalytic H 2 -evolution rate of 290 µmol h −1 g −1 in 10% triethanolamine aqueous solution under xenon light illumination. [28] Porous FPS nanosheets exhibit the photocatalytic H 2 -evolution activity of 305.6 µmol h −1 g −1 in 10% triethylamine aqueous solution with xenon light irradiation. [29] Nevertheless, to the best of our The aggravating extreme climate changes and natural disasters stimulate the exploration of low-carbon/zero-carbon alternatives to traditional carbonbased fossil fuels. Solar-to-hydrogen (STH) transformation is considered as appealing route to convert renewable solar energy into carbon-free hydrogen. Restricted by the low efficiency and high cost of noble metal cocatalysts, high-performance and cost-effective photocatalysts are required to realize the realistic STH transformation. Herein, the 2D FePS 3 (FPS) nanoshee...

Figure 7. a,b) Schematic illustrations of the O 2 flow supply for the photocatalyst in biphase (a) and triphase (b) systems for O 2 reduction and FFA oxidation.

Ammonia and nitrates are the most fundamental and significant raw ingredients in human society. Till now, industrial synthetic ammonia by Haber–Bosch process and industrial synthetic nitrates by the Ostwald process have encountered increasingly serious challenges, i.e., high energy consumption, high cost, and environment‐harmful gas emissions. Therefore, developing alternative approaches to achieve nitrogen fixation to overcome the inherent deficiencies of the well‐established Haber–Bosch and Ostwald processes has fascinated scientists for many years, especially the simultaneous formation of ammonia and nitrate directly from N2 molecules, which has been rarely studied. Herein, a heterojunction‐based photocatalytic system is designed to successfully achieve “overall nitrogen fixation,” a sustainable and simultaneous conversion of N2 molecules into ammonia and nitrate products under mild conditions. In this heterojunction, interfacial charge redistribution (ICR) promotes selective accumulations of photogenerated electrons and holes in the CdS and WO3 components. As a result, N2 molecules can be activated and reduced to ammonia products with yields of 35.8 µmol h−1 g−1 by a multi‐electron process, and synchronously oxidized into nitrate products with yields of 14.2 µmol h−1 g−1 by a hole‐induced oxidation coupling process. This work provides a novel insight and promising approach to realize artificial nitrogen fixation under mild condition.

Solar‐to‐hydrogen (STH) conversion through unassisted artificial photosynthesis (APS) devices is one of the promising and environmentally friendly strategies for sustainable development. However, the practical large‐scale application of the unassisted APS devices is impeded by the need for expensive noble metal‐based catalysts in photovoltaics and/or electrolyzers. Herein, well‐aligned 2D NixSy nanowalls (2D NixSy NWs) on a 3D nitrogen‐doped graphene foam (3D NGF) are synthesized and further employed it in unassisted APS. Due to the positive synergistic effect between the highly electrocatalytic activity of NixSy NW and excellent conductivity of NGF, this low cost material of (2D/3D) NixSy NW/NGF is highly efficient as a multifunctional catalyst in various applications: a counterelectrode for dye‐sensitized solar cell (DSSC) and a “bifunctional” electrocatalyst for oxygen and hydrogen evolution for electrocatalytic overall water splitting. Furthermore, three NixSy NW/NGF‐based DSSCs as a tandem cell for unassisted solar‐driven overall water splitting is connected, using NixSy NW/NGF itself on nickel foams as the anode and cathode. Impressively, such integrated photovoltaic‐electrolyzer APS device can achieve an STH efficiency of 3.2% with an excellent stability and low cost. This work opens an avenue to advanced multifunctional materials for the low‐cost and unassisted solar‐driven overall water splitting.

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