Immobilizing Ordered Oxophilic Indium Sites on Platinum Enabling Efficient Hydrogen Oxidation in Alkaline Electrolyte.

Addressing the sluggish kinetics in the alkaline hydrogen oxidation reaction (HOR) is a pivotal yet challenging step toward the commercialization of anion-exchange membrane fuel cells (AEMFCs). Here, we have successfully immobilized indium (In) atoms in an orderly fashion into platinum (Pt) nanoparticles supported by reduced graphene oxide (denoted as O-Pt3In/rGO), significantly enhancing alkaline HOR kinetics. We have revealed that the ordered atomic matrix enables uniform and optimized hydrogen binding energy (HBE), hydroxyl binding energy (OHBE), and carbon monoxide binding energy (COBE) across the catalyst. With a mass activity of 2.3066 A mg-1 at an overpotential of 50 mV, over 10 times greater than that of Pt/C, the catalyst also demonstrates admirable CO resistance and stability. Importantly, the AEMFC implementing this catalyst as the anode catalyst has achieved an impressive power output compared to Pt/C. This work not only highlights the significance of constructing ordered oxophilic sites for alkaline HOR but also sheds light on the design of well-structured catalysts for energy conversion.

In Situ Insertion of Silicon Nanowires into Hollow Porous Co/NC Polyhedra Enabling Large-Current-Density Hydrogen Evolution Electrocatalysis.

N-doped carbon (NC)-encapsulated transition metal (TM) nanocomposites are considered as alternatives to Pt-based hydrogen evolution reaction (HER) electrocatalysts; however, their poor electron transfer and mass diffusion capability at high current densities hinder their practical application. Herein, an oriented coupling strategy for the in situ grafting of ultrafine Co nanoparticle-embedded hollow porous C polyhedra onto Si nanowires (Co/NC-HP@Si-NWs) is proposed to address this concern. Experimental investigations reveal that the intimate coupling between the Si-NW and Co/NC nanocage forms a multithreaded conductive network, lowering the energy barrier for internal electron transfer. When functionalized as an HER electrocatalyst in 0.5 m H2 SO4 , Co/NC-HP@Si-NWs deliver overpotentials as low as 57 and 440 mV at 10 and 500 mA cm-2 , respectively, which are much better than those of the pristine Co/NC-HP. Moreover, Co/NC-HP@Si-NWs show an outstanding cycle durability of 24 h at 10 and 500 mA cm-2 . The findings of this study are expected to inspire revolutionary work on the development of Si-mediated TM-based electrocatalysts for the HER.

Emergent Intrinsic Ferromagnetism in Two-Dimensional Trigonal Rhodium Oxide.

Two-dimensional (2D) van der Waals single crystals with long-range magnetic order are the precondition and urgent task for developing a 2D spintronics device. In contrast to graphene and transition metal dichalcogenides, the study of 2D single-crystal metal oxides with intrinsic ferromagnetic properties remains a huge challenge. Here, we report a large-size trigonal single-crystal rhodium oxide (SC-Tri-RhO2), with crystal parameters of a = b = 3.074 Å, c = 6.116 Å, and a space group of P3̅m1 (164), exhibiting strong ferromagnetism (FM) at a rather high temperature. Furthermore, theoretical calculations suggest that the ferromagnetism in SC-Tri-RhO2 originates from spin splitting near the Fermi level, and the total magnetic moment is contributed mainly by the Rh atom.

Synergistic Active Heterostructure Design for Enhanced Two Electron Oxygen Reduction via Chemical and Electrochemical Reconstruction of Heterosulfides.

Transition metal sulfides, particularly heterostructures, represent a promising class of electrocatalysts for two electron oxygen reduction (2e- ORR), however, understanding the dynamic structural evolution of these catalysts during alkaline ORR remains relatively unexplored. Herein, NiS2/In2.77S4 heterostructure was synthesized as a precatalyst and through a series of comprehensive ex-situ and in-situ characterizations, including X-ray absorption spectroscopy, Raman spectroscopy, transient photo-induced voltage measurements, electron energy loss spectroscopy, and spherical aberration-corrected electron microscopy, it was revealed that nickel/indium (oxy)hydroxides (NiOOH/In(OH)3) could be evolved from the initial NiS2/In2.77S4 via both electrochemical and chemical-driven methods. The electrochemical-driven phase featured abundant bridging oxygen-deficient [NiO6]-[InO6] units at the interfaces of NiOOH/In(OH)3, facilitating a synergistic effect between active Ni and In sites, thus enabling an enhanced alkaline 2e- ORR capability than that of chemical-driven process. Remarkably, electrochemically induced NiOOH/In(OH)3 exhibited exceptional performance, achieving H2O2 selectivity of >90% across the wide potential window (up to 0.4 V) with a peak selectivity of >99%. Notably, within the flow cell, a current density exceeding 200 mA cm-2 was sustained for over 20 h, together with an impressive Faradaic efficiency of approximately 90% and a hydrogen peroxide production rate surpassing 4 mol g-1 h-1.

The Key Effect of Carboxyl Group and CuN2 O2 Coordinate Structure for Cu, N Co-Doped Carbon Dots with Peroxidase-Like Property.

Carbon dots (CDs) with good water solubility and biocompatibility have become a research hotspot in the nano-enzyme and biomedical field. However, the problems of low catalytic activity and ambiguous catalytic site of CDs as nanozymes still need to be addressed. In this work, CDs loaded with Cu single atoms are obtained through pyrolysis, and the coordination structure and surface functional groups are regulated by adjusting the pyrolysis temperature. CDs obtained at 300 °C (named Cu-CDs-300) have the most carboxyl content and Cu is coordinated in the form of CuN2 O2 , which can better decompose H2 O2 to produce free radical and is beneficial to catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). The vmax is 6.56*10-7  m s-1 , 6.56 times higher than that of horseradish peroxidase (HRP). Moreover, Cu-CDs-300 can effectively lead to CT26 apoptosis by generating much free radicals. This work demonstrates the synergistic effect of oxygen-containing functional groups and metal coordination structures on peroxide-like activity of CDs and provides new ideas for the design of clear active structure and high efficiency peroxide-like single atom CDs catalyst.

In Situ Coupling of Carbon Dots with Co-ZIF Nanoarrays Enabling Highly Efficient Oxygen Evolution Electrocatalysis.

Metal-organic frameworks (MOFs) are regarded as one promising class of precatalysts for electrocatalytic oxygen evolution reaction (OER), yet most of them suffer from poor conductivity and lack of coordinatively unsaturated metal sites, which hinders the fast electrochemical reconstruction and thus a poor OER activity. To address this issue, a unique heterocomposite has been constructed by in situ inserting carbon dots (CDs) into cobalt-based zeolitic imidazolate framework (Co-ZIF) nanosheet arrays (Co-ZIF/CDs/CC) in the presence of carbon cloth (CC) via one-pot coprecipitation for alkaline OER. Benefiting from the synergism between CDs and Co-ZIF subunits such as superior conductivity, strong charge interaction as well as abundant metal sites exposure, the Co-ZIF/CDs/CC exhibits an enhanced promotion effect for OER and contributes to the deep phase transformation from CDs-coupled Co-ZIF to CDs-coupled active CoOOH. As expected, the achieved Co-ZIF/CDs/CC only requires an overpotential of 226 mV to deliver 10 mA cm-2 in 1.0 M KOH, which is lower than that of Co-ZIF/CC and superior to most previously reported CC-supported MOF precatalysts. Moreover, it can also maintain a large current density of 100 mA cm-2 for 24 h with negligible activity decay.

Diversity and Tailorability of Photoelectrochemical Properties of Carbon Dots.

As a new kind of carbon based functional material, carbon dots (CDs) have sparked much interest in recent years. The tunable structure, composition, and morphology of CDs unlocks opportunities to enable diversity in their photoelectrochemical properties, and thus they show great potential in various applications such as biology, catalysis, sensors, and energy storage. Nevertheless, the related understanding of CDs is insufficient at present due to their inherent complexity of microstructure, which involves the intersection of high polymer, bulk carbon, and quantum dot (QD). A good understanding of the underlying mechanism behind the properties of CDs is still a formidable challenge, requiring the integration of robust knowledge from organic chemistry, materials science, and solid state physics. Within this context, discovering more appealing properties, elucidating fundamental factors that affect the properties and proposing effective engineering strategies that can realize specific functions for CDs are now highly pursued by researchers.At the beginning of this Account, the main features of CDs are introduced, where not only the basic structural, compositional and morphological characteristics but also the rich photoelectrochemical properties are elucidated, among which the band gap, chirality, photoinduced potential, and electron sink effect are particularly emphasized. Furthermore, new analysis techniques including transient photoinduced current (TPC), transient photoinduced voltage (TPV), and machine learning (ML) to reveal the unique properties of CDs are described. Then, several appealing strategies that aim to rationally tailor CDs for oriented applications are highlighted. These regulation strategies are morphology modulation (e.g., developing CDs with new geometrical configuration, controlling the particle size), phase engineering (e.g., altering the phase crystallinity, introducing the foreign atoms), surface functionalization (e.g., grafting various types of functional groups), and interfacial tuning (e.g., building CD-based nanohybrids with well-defined interfaces). Although the fundamental investigation of CDs is relatively undeveloped because of their complexity, this does not hinder their wide application. At the same time, exploring the extensive applications of CDs will promote their in-depth understanding. Finally, the chances for building a CD-centered blueprint for sustainable society are explored and challenges for future research in the field of CDs are proposed as follows: (i) the controllable synthesis of CDs with uniform size; (ii) search for novel CDs with unique structure, morphology, or composition; (iii) quantitative understanding of the property of CDs; (iv) performance enhancement by external forces such as magnetism or heat injection; (v) construction of the dual carbon concept; (vi) further research on different photocatalytic applications. On the whole, this Account may provide meaningful references for the understanding of the microstructure-property correlation as well as the regulation of CDs, thereby promoting their transition from fundamental research to practical application.

Oxygen Vacancy Engineering of Fe-Doped NiMoO4 for Electrocatalytic N2 Fixation to NH3.

Electrochemical nitrogen reduction reaction (NRR) is a promising method for ammonia synthesis under ambient conditions. However, the NRR performance is limited to an extremely strong N≡N bond in N2 and the competing hydrogen evolution reaction. Introducing oxygen vacancies (OVs) has been considered as a forceful means to accelerate the sluggish NRR reaction kinetics. Herein, we reported the design of Fe-doped NiMoO4 catalysts for NRR. Fe doping can increase the amount of OVs in the catalyst and contribute to lattice strain enhancement, thereby leading to the improvement of the electron transport rate and catalytic active for NRR. In 0.1 M Na2SO4 solution, the 5% Fe-NiMoO4 catalyst achieves a NH3 yield rate of 15.36 µg h-1 mgcat.-1 and a Faradaic efficiency of 26.85% under -0.5 V versus RHE. Furthermore, the 5% Fe-NiMoO4 catalyst exhibits excellent stability (up to 13 h) during the reaction.

Chiral Carbon Dots Derived from Serine with Well-Defined Structure and Enantioselective Catalytic Activity.

Carbon dots (C-Dots), with unique properties from tunable photoluminescence to biocompatibility, show wide applications in biotechnology, optoelectronic device and catalysis. Chiral C-Dots are expected to have strongly chirality-dependent biological and catalytic properties. For chiral C-Dots, a clear structure and quantitative structure-property relationship need to be clarified. Here, chiral C-Dots were fabricated by electrooxidation polymerization from serine enantiomers. The oxidized serine has a reversed chiral configuration to serine, which leads to the chiral C-Dots possessing inverse handedness compared with their raw materials. Electron circular dichroism spectrum, together with other diverse characterization techniques and theoretical calculations, confirmed that these chiral C-Dots (2-7 nm) have a well-defined primary structure of polycyclic dipeptide and possess a spatial structure with a c-axis of hexagonal symmetry and two cyclic dipeptides as the spatial structural unit. These chiral C-Dots also show enantioselective catalytic activity on DOPA enantiomers oxidation.

Metastable Hexagonal Phase SnO2 Nanoribbons with Active Edge Sites for Efficient Hydrogen Peroxide Electrosynthesis in Neutral Media.

Electrochemical two-electron oxygen reduction reaction (2 e- ORR) to produce hydrogen peroxide (H2 O2 ) is a promising alternative to the energetically intensive anthraquinone process. However, there remain challenges in designing 2 e- ORR catalysts that meet the application criteria. Here, we successfully adopt a microwave-assisted mechanochemical-thermal approach to synthesize hexagonal phase SnO2 (h-SnO2 ) nanoribbons with largely exposed edge structures. In 0.1 M Na2 SO4 electrolyte, the h-SnO2 catalysts achieve the excellent H2 O2 selectivity of 99.99 %. Moreover, when employed as the catalyst in flow cell devices, they exhibit a high yield of 3885.26 mmol g-1 h-1 . The enhanced catalytic performance is attributed to the special crystal structure and morphology, resulting in abundantly exposed edge active sites to convert O2 to H2 O2 , which is confirmed by density functional theory calculations.

Real-time monitoring the staged interactions between cationic surfactants and a phospholipid bilayer membrane.

The cationic surfactant-lipid interaction directs the development of novel types of nanodrugs or nanocarriers. The membrane action of cationic surfactants also has a wide range of applications. In this work, combining a photo-voltage transient method with the traditional dynamic giant unilamellar vesicle (GUV) leakage assay and molecular dynamics (MD) simulations, we monitored the molecular actions of a representative cationic surfactant, tetradecyl trimethyl ammonium bromide (TTAB), in a wide concentration range (i.e., 0.5 µM-10 mM), on a phospholipid bilayer membrane in real time. With low concentrations (e.g., ≤10 µM), TTAB performed a three-stage acting process, including the structural-disturbance-dominated, adsorption-dominated, and dynamic equilibrium stages. At higher concentrations (e.g., ≥100 µM), this process was accelerated to two stages. Furthermore, TTAB induced deformation and even rupture of the membrane, due to the asymmetric disturbance of surfactant molecules on the two leaflets of a bilayer. All these disturbances induced membrane permeabilization, and the times at which these transitions occurred are given. This work provides information on time and molecular mechanism during the membrane actions of cationic surfactants, and provides a simple and real-time method in studying the dynamic processes at the membrane interface.

Fabricating MAPbI3/MoS2 Composites for Improved Photocatalytic Performance.

Although lead halide perovskites are demonstrated to be promising photocatalysts for hydrogen evolution from hydrogen halide splitting, it still remains challenging to fabricate efficient and stable catalysts. Here MoS2 nanoflowers with abundant active sites are assembled with methylammonium lead iodide (MAPbI3) microcrystals to form a new heterostructure. Its hydrogen evolution rate can reach up to about 30 000 µmol g-1 h-1, which is more than 1000-fold higher than pristine MAPbI3 under visible light irradiation (λ ≥ 420 nm). Importantly, the solar HI splitting efficiency reaches 7.35%, one of the highest efficiencies so far. The introduction of MoS2 with proper band alignment and unsaturated species can efficiently promote the charge separation and afford more active sites for H2 production. This finding not only provides a highly efficient and stable photocatalyst for hydrogen evolution but also offers a useful modification strategy on lead halide perovskites.

Entropy Enhanced Perovskite Oxide Ceramic for Efficient Electrochemical Reduction of Oxygen to Hydrogen Peroxide.

The electrochemical oxygen reduction reaction (ORR) offers a most promising and efficient route to produce hydrogen peroxide (H2 O2 ), yet the lack of cost-effective and high-performance electrocatalysts have restricted its practical application. Herein, an entropy-enhancement strategy has been employed to enable the low-cost perovskite oxide to effectively catalyze the electrosynthesis of H2 O2 . The optimized Pb(NiWMnNbZrTi)1/6 O3 ceramic is available on a kilogram-scale and displays commendable ORR activity in alkaline media with high selectivity over 91 % across the wide potential range for H2 O2 including an outstanding degradation property for organic dyes through the Fenton process. The exceptional performance of this perovskite oxide is attributed to the entropy stabilization-induced polymorphic transformation assuring the robust structural stability, decreased charge mobility as well as synergistic catalytic effects which we confirm using advanced in situ Raman, transient photovoltage, Rietveld refinement as well as finite elemental analysis.

Copper-Bridged Tetrakis(4-ethynylphenyl)ethene Aggregates with Photo-Regulated 1 O2 and O2 .- Generation for Selective Photocatalytic Aerobic Oxidation.

Active species regulation is a key scientific issue that essentially determines the selectivity and activity of a photocatalyst. Herein, CuI -bridged tetrakis(4-ethynylphenyl)ethene aggregates (T4 EPE-Cu) with photo-regulated 1 O2 and O2 .- generation were demonstrated for selective photocatalytic aerobic oxidation. In this system, transient photovoltage combined with the density functional theory calculations confirmed that Cu-alkynyl was the main oxygen activation site. The adsorbed O2 tends to produce O2 .- because of the potential well effect of Cu-alkynyl under high-energy light excitation. But under low-energy light, O2 tends to produce 1 O2 via resonance energy transfer with Cu-alkynyl. For α-terpinene oxidation, the ratios of 1 O2 products to O2 .- products can be controlled from 1.3 (380 nm) to 10.7 (600 nm). Furthermore, T4 EPE-Cu exhibited ultrahigh photocatalytic performance for Glaser coupling and benzylamine oxidation, with a conversion and selectivity of over 99 %.

Pseudo-Periodically Coupling NiO Lattice with CeO Lattice in Ultrathin Heteronanowire Arrays for Efficient Water Oxidation.

Transition metal oxides (TMOs) have been under the spotlight as promising precatalysts for electrochemical oxygen evolution reaction (OER) in alkaline media. However, the slow and incomplete self-reconstruction from TMOs to (oxy)hydroxides as well as the formed (oxy)hydroxides with unmodified electronic structure gives rise to the inferior OER performance to the noble metal oxide ones. Herein, a unique dual metal oxides lattice coupling strategy is proposed to fabricate carbon cloth-supported ultrathin nanowires arrays, which are composed of pseudo-periodically welded NiO with CeO2 nanocrystals (NiO/CeO2 NW@CC). When served as an OER precatalyst in 1.0 m KOH, the NiO/CeO2 NW@CC shows an ultralow overpotential of 330 mV at 50 mA cm-2 , along with an impressive cycle durability of more than 3 days even at 50 mA cm-2 , surpassing CC-supported NiO and commercial IrO2 catalysts. The combined experimental and theoretical investigations unveil that the atomic coupling of CeO2 can not only appreciably trigger the generation of oxygen vacancies and expedite phase transformation of NiO into active NiOOH, but also in situ create a chemical bond with the formed NiOOH and enable the electron injection, thus effectively inhibiting the aggregation of the accessible NiOOH nanodomains and optimizing their reaction free energy towards oxygen-containing intermediates.

Photocatalytic selective H2release from formic acid enabled by CO2captured carbon nitride.

The selective decomposition of formic acid (FA) traditionally needs to be carried out under high temperature with the noble metal-based catalysts. Meanwhile, it also encounters a separation of H2and CO2for pure H2production. The photocatalytic FA dehydrogenation under mild conditions can meet a growing demand for sustainable H2generation. Here, we reported a photocatalytic selective H2release from FA decomposition at low temperature for pure H2production by Pt/g-C3N4. Low-cost and easy-to-obtained urea was utilized to produce carbon nitride as the metal-free semiconductor photocatalyst, along with a photodeposition to obtain Pt/g-C3N4. The electrochemical evidences clearly demonstrate the photocatalytic activity of Pt/g-C3N4to produce H2and CO2in one-step FA decomposition. And, the impedance is the lowest under simulated solar light of 70 mW cm-2with a faster electron transfer kinetic. Under simulated solar light, H2production rate is up to 1.59 mmol · h-1· g-1for FA with concentration at 2.65 mol l-1, 1700 000 times larger than that under visible light and 1928 times under ultraviolet (UV) light. DFT calculations further elucidate that nitrogen (N) active site at the g-C3N4has an excellent adsorption towards CO2molecule capture. Then, H2molecules are selectively released to simultaneously separate H2and CO2in solution. Platinum (Pt) at Pt/g-C3N4as the catalytic site contributes into the acceleration of H2production.

Photocatalyst for High-Performance H2 Production: Ga-Doped Polymeric Carbon Nitride.

A photocatalyst system is generally comprises a catalyst and cocatalyst to achieve light absorption, electron-hole separation, and surface reaction. It is a challenge to develop a single photocatalyst having all functions so as to lower the efficiency loss. Herein, the active GaN4 site is integrated into a polymeric carbon nitride (CN) photocatalyst (GCN), which displays an excellent H2 production rate of 9904 µmol h-1 g-1 . It is 162 and 3.3 times higher than that of CN with the absence (61 µmol h-1 g-1 ) and presence (2981 µmol h-1 g-1 ), respectively, of 1.0 wt % Pt. Under light irradiation the electron is injected and stored at the GaN4 site, where the LUMO locates. The HOMO distributes on the aromatic ring resulting in spatial charge separation. Transient photovoltage discloses the electron-storage capability of GCN. The negative GaN4 promotes proton adsorption in the excited state. The positive adsorption energy drives H2 desorption from GaN4 after passing the electron to the proton. This work opens up opportunities for exploring a novel catalyst for H2 production.

Carbon-Dot-Based White-Light-Emitting Diodes with Adjustable Correlated Color Temperature Guided by Machine Learning.

Here, we show the fabrication of the carbon dots (CDs) with green and orange emissions from PTCDA (perylene-3,4,9,10-tetracarboxylic dianhydride). Using these CDs as emitters, the orange (or green) CDs LEDs were fabricated, which show electroluminescence (EL) spectra centered at 560 nm (or 498 nm) with an external quantum efficiency (EQE) of 1.98 % (1.76 %) adhering a luminescence of 626 cd m-2 (or 519 cd m-2 ). The machine learning was successfully used to predict PL CCT value. With the model, the white photoluminescence (PL) emission with adjustable correlated color temperature (CCT) from 3093 to 11018 K via combining blue, green, and orange CDs was achieved. Then, we obtained the warm white CDs LEDs with CCT of 3107, 4071 and 4548 K, and cold white CDs LEDs with CCT of 5632 (CIE coordinates of (0.33, 0.33), EQE: 1.18 %, luminescence: 598 cd m-2 ) and 6034 K accurately.

Carbon Nitride Quantum Dots Enhancing the Anodic Electrochemiluminescence of Ruthenium(II) Tris(2,2'-bipyridyl) via Inhibiting the Oxygen Evolution Reaction.

Although electrochemiluminescence (ECL) has been developed significantly in the past few decades, ECL efficiency in aqueous solutions remains quite low. Determination of the energy losses and development of new ECL-enhancing strategies are still of great value. In this work, we discovered a detrimental nonradiation relaxation pathway by a concurrent oxygen evolution reaction (OER) process in a well-known ruthenium(II) tris(2,2'-bipyridyl) (Ru(bpy)32+) aqueous ECL system due to similar surface-sensitive characteristics, and for the first time, a chemical strategy was developed by which carbon nitride quantum dots (CNQDs) could inhibit the surface OER process, alleviate the energy losses by nonradiation relaxation, and enhance the anodic ECL of Ru(bpy)32+. In the Ru(bpy)32+/CNQD system, CNQDs could enhance the anodic ECL of Ru(bpy)32+ in a nitrogen stream (10-fold) and ambient air (161-fold). The luminous and nitrogen-rich CNQDs were also confirmed not to serve as ECL luminophores, anodic coreactants, or donor/acceptors in ECL. The coreactant-free Ru(bpy)32+/CNQD system possesses several advantages over the common coreactant ECL system, such as low dosage (100 µg/mL CNQDs), favorable regeneration capacity, etc. As an example, ECL on-off detection of dopamine utilizing the Ru(bpy)32+/CNQD system was also developed to show prospects in ECL sensing. Besides, CNQDs were introduced into the classical Ru(bpy)32+/C2O42- coreactant ECL system, leading to suppressed OER and improved ECL signal. Overall, the proposed new ECL-enhancing strategy is promising for applicable ECL sensing, could be extended to other ECL luminophores with high oxidation potential, and enables an in-depth understanding of the ECL process and mechanism.

Highly Efficient Photoreduction of Low-Concentration CO2 to Syngas by Using a Polyoxometalates/RuII Composite.

At present, the fixation of CO2 always requires it to be extracted from the atmosphere first, which leads to more energy consumption. Thus, direct photoreduction of low-concentration CO2 to useful chemicals (e.g., syngas) under sunlight is significant from an energy-saving and environmentally friendly perspective. Here, the design and fabrication of a [Ru(bpy)3 ]/[Co20 Mo16 P24 ] composite is demonstrated for visible-light-driven syngas production from diluted CO2 (3-20 %) gas with a high yield of approximately 1000 TONs (turnover number of syngas). This activity is an order of magnitude higher than the reported system with [Ru(bpy)3 ]2+ participation. With evidence from ultrafast transient absorption, GC-MS, 1 H NMR spectroscopy and in situ transient photovoltage tests, a clear and fundamental understanding of the highly efficient photoreduction of CO2 by the [Ru(bpy)3 ]/[Co20 Mo16 P24 ] composite is achieved. Making use of the structure and property designable polyoxometalates towards the photo-fixation of CO2 is a conceptually distinct and commercially interesting strategy for making useful chemicals and environmental protection.