Dual-atom-site catalysts (DACs) have emerged as an ew frontier in heterogeneous catalysis because the synergistic effect between adjacent metal atoms can promote their catalytic activity while maintaining the advantages of singleatom-site catalysts,such as almost 100 %atomic efficiency and excellent hydrocarbon selectivity.I nt his study,c obalt-based atom site catalysts with aC o 2 -N coordination structure were synthesized and used for photodriven CO 2 reduction. The resulting CoDAC containing 3.5 %C oa toms demonstrated asuperior atom ratio for CO 2 reduction catalytic performance, with 65.0 %C H 4 selectivity,w hichf ar exceeds that of cobaltbased single-atom-site catalysts (CoSACs). The intrinsic reason for the superior activity of CoDACsisthe excellent adsorption strength of CO 2 and CO* intermediates at dimeric Co active sites.

Herein we report simple, low-cost and scalable preparation of reduced graphene oxide (rGO) supported surfactant-free Cu2O-TiO2 nanocomposite photocatalysts by an ultrasound assisted wet impregnation method. Unlike the conventional preparation techniques, simultaneous reduction of Cu(2+) (in the precursor) to Cu(+) (Cu2O), and graphene oxide (GO) to rGO is achieved by an ultrasonic method without the addition of any external reducing agent; this is ascertained by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. UV-visible diffused reflectance spectroscopy (DRS) studies (Tauc plots) provide evidence for the loading of Cu2O tailoring the optical band gap of the photocatalyst from 3.21 eV to 2.87 eV. The photoreactivity of the as-prepared Cu2O-TiO2/rGO samples is determined via H2 evolution from water in the presence of glycerol as a hole (h(+)) scavenger under visible light irradiation. Very interestingly, the addition of rGO augments the carrier mobility at the Cu2O-TiO2 p-n heterojunction, which is evidenced by the significantly reduced luminescence intensity of the Cu2O-TiO2/rGO photocatalyst. Hence rGO astonishingly enhances the photocatalytic activity compared with pristine TiO2 nanoparticles (NPs) and Cu2O-TiO2, by factors of ∼14 and ∼7, respectively. A maximum H2 production rate of 110 968 μmol h(-1) gcat(-1) is obtained with a 1.0% Cu and 3.0% GO photocatalyst composition; this is significantly higher than previously reported graphene based photocatalysts. Additionally, the present H2 production rate is much higher than those of precious/noble metal (especially Pt) assisted (as co-catalysts) graphene based photocatalysts. Moreover, to the best of our knowledge, this is the highest H2 production rate (110 968 μmol h(-1) gcat(-1)) achieved by a graphene based photocatalyst through the splitting of water under visible light irradiation.

Facile preparation of metal–organic framework (MOF) derived earth-abundant nickel phosphide (Ni2P) by a simple, cost-effective procedure is described. Ni2P is recognized as a suitable replacement for expensive noble metal cocatalysts used for H2 production by water splitting. Ni2P nanoparticles were used to prepare a Ni2P/CdS composite with improved photocatalytic properties. Crystal structure and surface morphology studies showed that Ni-MOF spheres readily transform into Ni2P particles, and TEM images indicated the presence of Ni2P nanoparticles on CdS. The optical properties and charge carrier dynamics of the composite material exhibited better visible light absorption and improved suppression of charge carrier recombination. X-ray photoelectron spectra confirmed the presence of Ni2P on CdS. The synthesized materials were tested for photocatalytic hydrogen production with lactic acid as a scavenger under irradiation in a solar simulator. The rate of H2 production with Ni2P/CdS was 62 times greater than that with pure CdS. The superior activity of the composite material is attributed to the ability of Ni2P to separate the photoexcited charge carriers from CdS and provide good electrical conductivity. The optimized composite material also exhibited better photocatalytic activity than Pt cocatalyzed CdS. Based on the experimental results, a possible electron–hole transfer mechanism is proposed.

No abstract

Solar-driven photocatalytic hydrogen evolution is important to bring solar-energy-to-fuel energy-conversion processes to reality. However, there is a lack of highly efficient, stable, and non-precious photocatalysts, and catalysts not designed completely with expensive noble metals have remained elusive, which hampers their large-scale industrial application. Herein, for the first time, a highly efficient and stable noble-metal-free CdS/WS -MoS nanocomposite was designed through a facile hydrothermal approach. When assessed as a photocatalyst for water splitting, the CdS/WS -MoS nanostructures exhibited remarkable photocatalytic hydrogen-evolution performance and impressive durability. An excellent hydrogen evolution rate of 209.79 mmol g h was achieved under simulated sunlight irradiation, which is higher than the values for CdS/MoS (123.31 mmol g h ) and CdS/WS nanostructures (169.82 mmol g h ) and the expensive CdS/Pt benchmark catalyst (34.98 mmol g h ). The apparent quantum yield reached 51.4 % at λ=425 nm in 5 h. Furthermore, the obtained hydrogen evolution rate was better than those of several noble-metal-free catalysts reported previously. The observed high rate of hydrogen evolution and remarkable stability may be a result of the ultrafast separation of photogenerated charge carriers and transport between the CdS nanorods and the WS -MoS nanosheets, which thus increases the number of electrons involved in hydrogen production. The proposed designed strategy is believed to potentially open a door to the design of advanced noble-metal-free photocatalytic materials for efficient solar-driven hydrogen production.