The present study aimed to characterize key physico-chemical and mineralogical attributes of magnetite iron (Fe) ore tailings to identify potential constraints limiting in situ soil formation and direct phytostabilization. Tailings of different age, together with undisturbed local native soils, were sampled from a magnetite mine in Western Australia. Tailings were extremely alkaline (pH> 9.0), with a lack of water stable aggregate and organic matter, and contained abundant primary minerals including mica (e.g., biotite), with low specific surface area (N-BET around 1.2 m g). These conditions remained relatively unchanged after four years' aging under field conditions. Chemical extraction and spectroscopic analysis [e.g., X-ray diffraction (XRD) and synchrotron-based Fe K edge X-ray absorption fine structure spectroscopy (XAFS) analysis] revealed that the aging process decreased biotite-like minerals, but increased hematite and magnetite in the tailings. However, the aged tailings lacked goethite, a compound abundant in natural soils. Examination using backscattered-scanning electron microscope - energy dispersive X-ray spectrometry (BSE-SEM-EDS) revealed that aged tailings contained discrete sharp edged Fe-bearing minerals that did not physically integrate with other minerals (e.g., Si/Al bearing minerals). In contrast, Fe minerals in native soils appeared randomly distributed and closely amassed with Si/Al rich phyllosilicates, with highly eroded edges. The lack of labile organic matter and the persistence of alkaline-saline conditions may have significantly hindered the bioweathering of Fe-minerals and the biogenic formation of secondary Fe-minerals in tailings. However, there is signature that a native pioneer plant, Maireana brevifolia can facilitate the bioweathering of Fe-bearing minerals in tailings. We propose that eco-engineering inputs like organic carbon accumulation, together with the introduction of functional microbes and pioneer plants, should be adopted to accelerate bioweathering of Fe-bearing minerals as a priority for initiating in situ soil formation in the Fe ore tailings.

photosynthetic or solar-driven watersplitting systems, the oxygen evolution reaction (OER) is driven by a four-chargecarrier transfer pathway, while either carbon dioxide reduction or the hydrogen evolution reaction takes place on the counter electrode. However, this halfreaction (i.e., the OER) is regarded as the kinetic bottleneck for both artificial photosynthesis and overall water splitting because of the large energy requirements (i.e., large overpotentials) for driving the multielectron transfer processes. Fortunately, light-absorbing semiconductor devices that utilize small bandgap materials, such as Si, GaAs, or GaP, have been demonstrated to be efficient photoelectrodes for achieving high performance catalysis of the OER [5,6] owing to their wide absorption region in the visible light spectrum. Nevertheless, the utilization of these small band gap materials has commonly suffered from the considerable issue of their valance bands having characteristically low driving forces, thereby leading to poor transfer of the charge carriers needed for water oxidation. The dynamic behavior of the photoinduced charge-carrier separation is a critical factor for addressing both the overpotential requirement and poor driving force to effectively facilitate the transport of the excited minority carriers (i.e., holes) towardThe integration of surface metal catalysts with semiconductor absorbers to produce photocatalytic devices is an attractive method for achieving high-efficiency solar-induced water splitting. However, once combined with a photoanode, detailed discussions of the light-induced processes on metal/semiconductor junction remain largely inadequate. Here, by employing in situ X-ray scattering/ diffraction and absorption spectroscopy, the generation of a photoinduced adaptive structure is discovered at the interfacial metal-semiconductor (M-S) junction between a state-of-the-art porous silicon wire and nickel electrocatalyst, where oxygen evolution occurs under illumination. The adaptive layer in M-S junction through the light-induced activation can enhance the voltage by 247 mV (to reach a photocurrent density of 10 mA cm −2 ) with regard to the fresh photoanode, and increase the photocurrent density by six times at the potential of 1.23 V versus reversible reference electrode (RHE). This photoinduced adaptive layer offers a new perspective regarding the catalytic behavior of catalysts, especially for the photocatalytic water splitting of the system, and acting as a key aspect in the development of highly efficient photoelectrodes.

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A new tender X-ray absorption spectroscopy beamline for operating over the photon energy range from 1.7 keV to 11 keV is under construction at port 32 of the Taiwan Photon Source (TPS). The TPS 32A beamline uses two back-to-back water-cooled double crystal monochromators (DCMs), InSb(111) and Si(111), for achieving the wide energy tunability. The beamline design takes advantage of the low emittance of the TPS accelerator and a bending magnet (BM) to obtain a high-brightness focussed beam. In order to overcome the issue of poor thermal conductivity of InSb(111) crystals while facing high thermal load, we have implemented the following features : (i) we have controlled the flux and heat load by optimizing the source collection angle of 2 × 0.15 mrad2 (h × v), and (ii) we have installed water cooled double-bounce high harmonic rejection mirrors (HHRMs) with a variable incidence angle upstream of the DCM to reduce the heat load on the first InSb crystal. The DCM is followed by a 2:1 toroidal focusing mirror (TFM) which focuses the beam parallel to the floor of the experimental endstation. The simulated focus beam size is 0.9 × 0.9 mm2 (h × v, FWHM) using the InSb(111) DCM at 1.7 keV, and 0.2 × 0.45 mm2 (h × v, FWHM) using the Si(111) DCM at 4 keV, respectively. The photon flux is 1010 -1012 photons s−1 in the energy range of 1.7 to 11 keV at the sample stage after passing through the Be windows. The design parameters of photon flux and beam spot size will facilitate a tender X-ray source for carrying out high-quality X-ray absorption spectroscopy experiments.

The Taiwan Photon Source (TPS) with high brightness and energy tunability is suitable for applications in spectroscopy. The tender X-ray absorption beamline will be optimized for X-ray absorption spectroscopy measurements using a bending-magnet source in a unique photon energy range (1.7–10 keV) and two crystal pairs [InSb(111) and Si(111)] separated using back-to-back double-crystal monochromators (DCMs). InSb crystals are typically used in the lower photon energy range of 1.7–3.5 keV. However, the poor thermal conductivity of InSb crystals leads to severe deformation. This factor should be considered when the monochromator is installed on a tender X-ray beamline in a storage ring with a high power density. There are many approaches to reducing the thermal load on the first crystal of a DCM. Double-bounce high harmonics rejection mirrors in front of the DCM serve not only to reduce the high-order harmonics but also to absorb considerable quantities of heat. Two coating stripes on the silicon surfaces with a variable incident angle will be key to solving the thermal load on this beamline.