Direct Growth of Flexible and Scalable Photocathodes from α-Brass Substrates

Abstract

A facile, low cost method to grow robust and adherent, single phase metal oxides from an earth-abundant binary alloy has been outlined and its effectiveness as a photocathode for solar energy harvesting demonstrated. Cu 0.7 Zn 0.3 (α-brass) foils were thermally dezincified (removal of surface Zn) at 450°C and subsequently oxidized, by varying the temperature from 300 to 600°C. The brass foil served as the oxide growth substrate as well as a conductive electrical contact for subsequent photoelectrochemical testing. CuO nanowires were seen for the 400 and 500°C samples. ZnO phase was detected within the concave pores on the sample surface. The highest photocurrent of 1.8 mA/cm 2 at −0.5 V vs Ag/ AgCl occurred for the sample oxidized at 500°C with an incidentphoton-to-current-efficiency (IPCE) of 6.9% at 450 nm. This sample corresponds to the oxide with the lowest surface zinc content (10 at. %, measured by X-ray photoelectron spectroscopy), indicating that the presence of ZnO hinders the performance of the photocathode. The approach demonstrated in this work opens up possibilities for making large area, scalable photoelectrodes directly on conductive alloy substrates, leading to simpler electrode fabrication and opportunities for alloy recycling for sustainable energy harvesting.

Arrays Formation of Zinc Oxide Nano-Objects with Varying Morphology for Sensor Applications

“…For the first time, a notable increase in the diffusion coefficient (several times as compared to heat exposure of the laser beam only) in the metallic material, caused by the synergy of heat exposure and vibrations induced by laser, predominantly in the range of sound frequencies, as a result of a pulse-periodic laser irradiation with a pulse duration in the milli- and microsecond range, was described. The oxide nanostructures obtained as result of thermal oxidation of metallic materials show high purity since this approach eliminates the need for chemical catalytic synthesis [ 41 ]. It should be mentioned that ZnO nanostructures were synthesized simultaneously on the substrate by directly heating brasses in air and this was described in Reference [ 42 ].…”

Model based prediction of nanostructured thin film morphology in an aerosol chemical vapor deposition process

“…Nanostructured thin films synthesis has attracted enormous interest in the past several decades 39 due to their wide array of applications including solar photovoltaics [2][3][4], solar water-splitting [1,[5][6][7][8][9][10][11], CO 2 photoreduction [12,13], and lithium-ion batteries [14]. Various approaches have 41 been used to synthesize these nanostructured films, such as, thermal oxidation [15], vapor-liquid solid (VLS) growth [16], template-based synthesis [17], electrochemical methods [18] and gas phase methods [1,19,20]. Among these methods, gas phase synthesis such as flame aerosol deposition [19], particle-precipitation chemical vapor deposition (PP-CVD) [21], and aerosol 45 chemical vapor deposition (ACVD) [22] present a rapid, scalable and low-cost method of 46 synthesizing nanostructured thin films.…”

Amorphous Cu2-δO as Passivation Layer for Ultra Long Stability of Copper Oxide Nanowires in Photoelectrochemical Environments

“…Photoelectrochemical (PEC) hydrogen generation [1][2][3][4][5] is envisioned as one of the more efficient and scalable platforms for renewable, solar-to-fuel conversion. However, despite significant advances in efficiency, up to 16% with multi-junction cells, 6 the poor stability of the photoelectrodes in aqueous solutions 7 has hindered large scale commercial deployment. The US Department of Energy targets a 20% solar-to-hydrogen conversion efficiency with a 10 year electrode replacement lifetime by 2020 for PEC hydrogen generation to be competitive with alternate hydrogen generation technologies.…”

“…Examples of passivation layers that have been used are carbon, 12 CuO on Cu 2 O, 13 Al-doped ZnO and TiO 2, 14 Ga 2 O 3 15 and TiO 2, SnO 2 17 and CuS. 18 These passivation layers have been specifically used on copper oxide based absorber materials -Cu 2 O and CuO, which are attractive candidates for photocathodes 7,19 but ones that show a strong propensity for photoreduction 20 to metallic Cu. Although copper oxide photocathodes show stability improvements, the passivation strategies involve deposition of heterogeneous materials and give rise to additional interfaces and complexities brought by presence of defects, [21][22][23][24][25] material intermixing and crystal lattice mismatch with the underlying photoelectrode 26 leading to charge recombination and lower efficiencies.…”