Investigation of enhanced electro-catalytic HER/OER performances of copper tungsten oxide@reduced graphene oxide nanocomposites in alkaline and acidic media

In this paper, we investigate electro-catalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) of synthesized copper tungsten oxide@reduced graphene oxide (CuWO4@rGO) nanocomposites. The prepared CuWO4@rGO nanocomposites show bifunctional...

Recycling Rusty Iron with Natural Zeolite Heulandite to Create a Unique Nanocatalyst for Green Hydrogen Production

Corrosion-induced iron rust causes severe danger, pollution, and economic problems. In this work, nanopowders of Fe2O3 and Fe2O3/zeolite are synthesized for the first time using rusted iron waste and natural zeolite heulandite by chemical precipitation. The chemical composition, nanomorphologies, structural parameters, and optical behaviors are investigated using different techniques. The Fe2O3/zeolite nanocomposite showed smaller sizes and greater light absorption capability in visible light than Fe2O3 nanopowder. The XRD pattern shows crystalline hematite (α-Fe2O3) with a rhombohedral structure. The crystallite sizes for the plane (104) of the Fe2O3 and Fe2O3/zeolite are 64.84 and 56.53 nm, respectively. The Fe2O3 and Fe2O3/zeolite have indirect bandgap values of 1.87 and 1.91 eV and direct bandgap values of 2.04 and 2.07 eV, respectively. Fe2O3 and Fe2O3/zeolite nanophotocatalysts are used for solar photoelectrochemical (PEC) hydrogen production. The Fe2O3/zeolite exhibits a PEC catalytic hydrogen production rate of 154.45 mmol/g.h @ 1 V in 0.9 M KOH solution, which is the highest value yet for Fe2O3-based photocatalysts. The photocurrent density of Fe2O3/zeolite is almost two times that of Fe2O3 catalyst, and the IPCE (incident photon-to-current conversion efficiency) reached ~27.34%@307 nm and 1 V. The electrochemical surface area (ECSA) values for Fe2O3 and Fe2O3/zeolite photocatalysts were 7.414 and 21.236 m2/g, respectively. The rate of hydrogen production for Fe2O3/zeolite was 154.44 mmol h−1/g. This nanophotocatalyst has a very low PEC corrosion rate of 7.6 pm/year; it can retain ~97% of its initial performance. Therefore, the present research can be applied industrially as a cost-effective technique to address two issues at once by producing solar hydrogen fuel and recycling the rusted iron wires.

Grain-boundary-rich Pt nanoparticle assembly for catalytic hydrogen sensing at room temperature

We report a facile method of synthesizing grain-boundary(GB)-rich platinum nanoparticle assembly. GBs are formed between platinum nanoparticles during their random collision and attachment in solution driven by water electrolysis. The GB-rich nanoparticle assembly exhibits ~400-fold higher catalytic hydrogen oxidation rate than platinum nanoparticles before assembly, enabling catalytic hydrogen sensing at room temperature without external heating. Our sensor also demonstrates fast response/recovery (~7 s at >1% H2), nearly no signal variation during a 280-hour-long stability test, and high selectivity toward hydrogen over 36 interference gases. Furthermore, this sensor can be easily fabricated from commercial thermometers at a low cost (< $5 per unit). Theoretical calculation results reveal that the high performance of GB-rich platinum nanoparticle assembly arises from tensile strain at the GBs.

Coexisting multi-states in catalytic hydrogen oxidation on rhodium

Catalytic hydrogen oxidation on a polycrystalline rhodium foil used as a surface structure library is studied by scanning photoelectron microscopy (SPEM) in the 10−6 mbar pressure range, yielding spatially resolved X-ray photoemission spectroscopy (XPS) measurements. Here we report an observation of a previously unknown coexistence of four different states on adjacent differently oriented domains of the same Rh sample at the exactly same conditions. A catalytically active steady state, a catalytically inactive steady state and multifrequential oscillating states are simultaneously observed. Our results thus demonstrate the general possibility of multi-states in a catalytic reaction. This highly unusual behaviour is explained on the basis of peculiarities of the formation and depletion of subsurface oxygen on differently structured Rh surfaces. The experimental findings are supported by mean-field micro-kinetic modelling. The present observations raise the interdisciplinary question of how self-organising dynamic processes in a heterogeneous system are influenced by the permeability of the borders confining the adjacent regions.