Volume 2, Issue 3, Pages 549-557 (March 2018) Ultrasmall CoP Nanoparticles as Efficient Cocatalysts for Photocatalytic Formic Acid Dehydrogenation  Shuang Cao, Yong Chen, Hui Wang, Jie Chen, Xinghua Shi, Hongmei Li, Ping Cheng, Xinfeng Liu, Min Liu, Lingyu Piao  Joule  Volume 2, Issue 3, Pages 549-557 (March 2018) DOI: 10.1016/j.joule.2018.01.007 Copyright © 2018 Elsevier Inc. Terms and Conditions

Joule 2018 2, 549-557DOI: (10.1016/j.joule.2018.01.007) Copyright © 2018 Elsevier Inc. Terms and Conditions

Figure 1 Computational Investigation and Gas Adsorption-Desorption Test (A) Calculated energy profile for hydrogen production on CoP (101) surface. The energy change for 2H+ + e− → H2 is defined as zero energy line. The relative energies are plotted with respect to the zero reference. (B) The optimized structures of the initial states (IS), transition state (TS), and final state (FS), as labeled in (A). (C and D) Gas adsorption-desorption test for (C) CoP and (D) Pt coated electrode at 1 V. The experiments were conducted in the indicated order. Joule 2018 2, 549-557DOI: (10.1016/j.joule.2018.01.007) Copyright © 2018 Elsevier Inc. Terms and Conditions

Figure 2 Synthesis Schematic and Material Characterization (A) Schematic illustration of the CdS/CoP@RGO hybrid synthesis. (B) TEM and HRTEM (inset) images of the obtained Co3O4@SiO2 NPs. (C–I) TEM images of (C) Co3O4@SiO2/RGO, (D) Co3O4@RGO, (F) CoP@RGO, and (H) CdS/CoP@RGO. HRTEM images of (E) Co3O4@RGO, (G) CoP@RGO, and (I) CdS/CoP@RGO hybrids. Joule 2018 2, 549-557DOI: (10.1016/j.joule.2018.01.007) Copyright © 2018 Elsevier Inc. Terms and Conditions

Figure 3 Photocatalytic Measurements for FA Dehydrogenation (A) Visible light-driven H2 production as a function of CoP contents in 4.0 M FA aqueous solution. (B) H2 evolution in various solutions with different FA concentrations. (C) Comparison of CdS/CoP@RGO (8.3 wt%) with other similar systems for photocatalytic dehydrogenation of FA in aqueous solution (the detailed information is shown in Table S2). (D) Photocatalytic comparison of CdS loaded with different noble-metal@RGO cocatalysts under same experimental conditions with CoP@RGO. The weight ratios of Pt, Pd, Au, and Ru in the final hybrids are 8.3 wt%. (E) Photocatalytic durability test for CdS/CoP@RGO (8.3 wt%) in 6.6 M FA aqueous solution. CdS (1 mg) was added after 120 hr of irradiation. All experiments are conducted in 20 mL of solution with 1 mg of hybrid catalyst, and the error bars are representative of three independent experiments. Joule 2018 2, 549-557DOI: (10.1016/j.joule.2018.01.007) Copyright © 2018 Elsevier Inc. Terms and Conditions

Figure 4 Metallic Property Exploration and Photogenerated Electron Transfer Investigation (A and B) XPS spectra of (A) Co 2p3/2 and (B) P 2p for the CoP@RGO hybrid. (C) Current-voltage curve for CoP film. (D and E) Steady-state PL (D) and TRPL (E) spectra for CdS, CdS@RGO, and CdS/CoP@RGO. The excitation wavelengths are 415 nm and 390 nm for PL and TRPL, respectively. Joule 2018 2, 549-557DOI: (10.1016/j.joule.2018.01.007) Copyright © 2018 Elsevier Inc. Terms and Conditions

Figure 5 Proposed Mechanism for Photocatalytic FA Dehydrogenation by CdS/CoP@RGO Hybrid The CoP NPs serve as the H2 production active sites, and the COOH− anion is oxidated by·OH radicals and the photogenerated holes on the VB band of CdS. Joule 2018 2, 549-557DOI: (10.1016/j.joule.2018.01.007) Copyright © 2018 Elsevier Inc. Terms and Conditions