The high entropy alloy (HEA) nanoparticles have been prepared using cast cum cryo-milling process. In which, the Au, Ag, Pd, Pt and Cu (99.9 at. % pure, Alfa Aesar, USA) melted under argon environment to synthesize cast HEAs and afterwardcast HEA have been milled in cryomill for 6 hours. The detailed synthesis process can be found elsewhere. 1 The cryomilled powder (HEA nanoparticles) has been characterizedin order tothe crystalline phase, size, chemical homogeneity, composition, and catalyst activity. The X-ray diffraction recorded using Panalytical empyrean ( max =1.54056 A),and size of nanoparticles have been estimated using Transmission electron microscope (FEI, Technai G 2 , UT 20 operated at 200

No abstract

Thin (~50 nm) film hematite photoanodes doped with different dopants at a concentration of 1 cation% display internal solar to chemical (ISTC) conversion efficiency in the following order: Sn > Nb > Si > Pt > Zr > Ti > Zn > Ni > Mn.

No abstract

Transparent Fe1-xNixOOH overlayers (~2 nm thick) were deposited photoelectrochemically on (001) oriented heteroepitaxial Sn-and Zn-doped hematite (α-Fe2O3) thin film photoanodes. In both cases, the water photo-oxidation performance was improved by the co-catalyst overlayers. Intensity modulated photocurrent spectroscopy (IMPS) was applied to study the changes in the hole current and recombination current induced by the overlayers. For the Sn-doped hematite photoanode, the improvement in performance after deposition of the Fe1-xNixOOH overlayer was entirely due to reduction in the recombination current, leading to a cathodic shift in the onset potential. For the Zn-doped hematite photoanode, in addition to a reduction in recombination current, an increase in the hole current to the surface was also observed after the overlayer deposition, leading to a cathodic shift in the onset potential as well as an enhancement in the plateau photocurrent. These results demonstrate that Fe1-xNixOOH cocatalysts can play different roles depending on the underlying hematite photoanode. The effect of the cocatalyst is not always limited to changes in the surface properties, but also to an increase in hole current from the bulk to the surface that indicates a possible crosslink between surface and bulk processes. Manuscript Hematite (-Fe2O3) is an attractive material for solar water splitting based on its favorable properties as a photoanode material in photoelectrochemical (PEC) cells. 1 However, the performance of state-of-theart hematite photoanodes 2-5 is still far short of the maximum theoretical efficiency, both in terms of photocurrent and photovoltage. One route for improving photoanode performance is through use of various co-catalysts which reduce the overpotential for water photo-oxidation, thereby leading to a cathodic shift in the applied bias. 6-9 One of the most promising materials for use as a co-catalyst is earth abundant Fe1-xNixOOH. For the remainder of the manuscript, we will refer to Fe1-xNixOOH as "FeNiOx", a commonly used abbreviation. FeNiOx overlayers have shown similar improvements in photoelectrochemical performance as more expensive IrOx based co-catalysts. 10 FeNiOx overlayers can be produced easily by a variety of methods 11-15 and they are stable in alkaline solutions, 12 as the oxyhydroxide phase Fe1-xNixOOH. 16 In addition, it has recently been shown 17 that using a photoelectrochemical deposition method, very thin and transparent FeNiOx overlayers can be deposited to avoid optical (absorption) losses in the photoanode. Significant cathodic shifting of the onset potential for water photo-oxidation is typically observed for FeNiOx coated hematite photoanodes. 18,19 Generally, the changes in performance have been attributed to a reduction in the surface recombination either as a result of surface passivation, 20 hole storage in the overlayer, 21 or p-n junction formation. 22 For ultrathin photoelectrodeposited FeNiOx overlayers, improved catalysis has been suggested as the reason for improvement. 17 I...