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Although great advances have been achieved in the field of electrocatalysis, the design of highly efficient and stable earth-abundant electrocatalysts for overall water splitting remains a significant challenge. Herein, we have successfully developed cost-efficient three dimensional (3D) highly open hierarchical catalysts with cobalt-molybdenum nanosheet arrays on nickel foam (NF) (denoted as CoMoO NSs@NF) and CoMoP NSs@NF via phosphorization for efficient overall water splitting. The optimized Co 5 Mo 1.0 O NSs@NF exhibits excellent OER activity with low overpotentials of 270 mV at 10 mA cm −2 and superior stability after 140 h and the optimized Co 5 Mo 1.0 P NSs@NF shows excellent HER activity with low overpotential of 173 mV at 10 mA cm −2 and superior stability after 1000 CV cycles. In addition to the enhanced electron migration and mass transfer benefited from the 3D structure, the XPS analysis shows that Mo plays a vital role on modulating the number of active sites on the surface, leading to the electrocatalytic enhancement. Significantly, the Co 5 Mo 1.0 O NSs@NF//Co 5 Mo 1.0 P NSs@NF couple showed highly efficient overall water electrolysis with a low potential of 1.68 V at 10 mA cm −2 in an alkaline electrolyzer as well as excellent stability after long-term water splitting, holding great potential for practical overall water splitting electrocatalysis. [ABSTRACT FROM AUTHOR]

Rational design of bifunctional two-dimensional (2D) heterostructures with excellent activity and durability remains a great challenge for electrocatalytic water splitting. Herein, we propose a topochemical domain engineering to realize 2D mosaic heterostructures with ultrafine phosphide nanodomains highly dispersed on the surface of Ru doped CoMoO 4 nanosheets (denoted as Ru-CMOP), which are vertically interconnected on the conductive skeleton assembling a 3D array structure. The as-prepared Ru-CMOP electrocatalyst exhibits excellent activity and long-term stability with the overpotentials of 114 and 286 mV at 100 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH solution, respectively, outperforming most reported metal phosphide-based bifunctional heterostructures. Moreover, an assembled electrolyzer using the Ru-CMOP as anode and cathode simultaneously delivers cell voltages of 1.697 V and 1.828 V to achieve 100 mA cm−2 and 500 mA cm−2, respectively, with outstanding durability at 250 mA cm−2 for 120 h. Density functional theory calculations and experimental results indicate that the strongly coupled heterointerfaces with built-in electric field can facilitate electron transfer while multi-porous nanosheet arrays contribute to active sites exposure and mass/gas transport, thereby synergistically accelerating the reaction kinetics. Additionally, combining with a commercial silicon photovoltaic solar cell, the electrolyzer can be efficiently and robustly established, demonstrating the great potential for practical photovoltaic-electrolysis applications. [Display omitted] • 2D mosaic heterostructures are prepared by topochemical domain engineering. • The Ru-CMOP exhibits outstanding activity and stability for HER and OER in alkaline media. • The rich heterointerfaces optimize the electronic configuration, indicated by DFT calculations. • A solar-cell-driven overall water-splitting device is efficiently constructed. [ABSTRACT FROM AUTHOR]

B-type carbonate apatite (CO3Ap) block may be an ideal artificial bone substitute because it is closer in chemical composition to bone mineral. In the present study, the feasibility to fabricate CO3Ap blocks was investigated using compositional transformation, which was based on the dissolution-precipitation reaction of a gypsum-calcite composite with free-molding behavior. For the compositional change, or phosphorization, gypsum-calcite composites of varying CaCO3 contents were immersed in 1 mol/L (NH4)3PO4 aqueous solution at 100°C for 24 hours. No macroscopic changes were found after the treatment, whereas microscopic change was observed at SEM level. X-ray diffraction, Fourier transform infrared spectroscopy and CHN analysis indicated that the composites were B-type CO3Ap containing approximately 6-7 wt% of CO3, a value similar to that of biological bone apatite. Diametral tensile strength of the CO3Ap block was approximately 1-3 MPa. Based on the results obtained, it was therefore concluded that gypsum-calcite was a good candidate for the fabrication of CO3Ap blocks, coupled with the advantage that the composite can be molded to any shape by virtue of the setting property of gypsum. [ABSTRACT FROM AUTHOR]