Mourad Frites

A Single Chip Standalone Water Splitting Photoelectrochemical Cell

Water splitting photoelectrochemical cell (PEC) was fabricated in which the electrolyzer parts were made on a single chip. This was achieved by depositing an optically transparent Mn-oxide-TiO 2 thin layer on the front of a triple junction amorphous Si photovoltaic cell which acted as the anode and the back stainless steel layer acted as the cathode under illumination of light. This single chip water electrolysis cell operates like an artificial leaf. Water splitting was observed by simply submersing the device in a basic electrolyte solution under solar simulated light of 1 sun (0.1 W cm -2 ). This self-driven PEC was found to produce hydrogen gas at the rate of 12.42 L m -2 h -1 and a solar to hydrogen efficiency (STHE) of 3.25 % from the collected H 2 gas in 2.5 M KOH solution. No signs of degradation of this single chip PEC were observed during water splitting when the device was run continuously for 6 hours.

Photoelectrochemical Splitting of Water to H2 and O2 at n-Fe2O3 Nanowires and Nanocrystalline Carbon-Modified (CM)-n-Fe2O3 Thin Films

Iron oxide n-Fe2O3 nanowire thin films were synthesized by thermal oxidation of Fe metal sheet (Alfa Co. 0.25 mm thick) in an electric oven then tested for their photoactivity. The photoresponse of the n-Fe2O3 nanowires was evaluated by measuring the rate of water splitting reaction to hydrogen and oxygen, which was found to be proportional to photocurrent density, jp. The optimized electric oven-made n-Fe2O3 photoelectrodes showed photocurrent densities of 1.32 mA cm-2 at measured potential of 0.0 V/SCE with photoconversion efficiency of 1.69 % at applied potential of 0.70 V vs Eaoc (electrode potential at open circuit conditions) under illumination intensity of 100 mW cm-2 from a Solar simulator with a global AM 1.5 filter. The photoactivity was improved upon incorporation of carbon into the lattice of n-Fe2O3 by flame oxidation at 850{degree sign}C. The carbon modified (CM)-n-Fe2O3 showed enhanced photocurrent response to 3.14 mA cm-2 at a measured potential of 0.0 V/SCE with an efficiency of 2.23% at applied potential of 0.52 V vs Eaoc. The nanocrystalline CM-n- Fe2O3 and n-Fe2O3 nanowires thin films were characterized using photocurrent density measurements under monochromatic light illumination, UV-Vis spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM).

Efficient Anode and Cathode Materials for Amorphous Silicon Solar Cell Driven all Solar Electrolysis of Water

Abstract Few non-noble metal based anode and cathode materials were investigated for all solar electrolysis of water to hydrogen and oxygen gases powered by double junction amorphous silicon (Dj-a-Si) solar cell under solar simulated light of 1 sun. The highest hydrogen generation current efficiency of 58.68% was obtained when Pt wire was used as a cathode with the non-noble metal based Ni-Co3 O4 as an anode in the electrochemical cell. However, when Pt metal was replaced by a non-noble metal Ni as cathode, the maximum hydrogen generation current efficiency of 51.28% was observed. This corresponds to a 7.4% loss in current efficiency when Pt cathode was replaced by Ni. The percent solar to hydrogen conversion efficiencies (% STH) were found to be 8.66% and 7.57% for the Dj-a-Si solar cell driven electrolysis of water in the Ni-Co3O4‖Pt and non-noble metal based Ni-Co3O4‖Ni electrochemical cells respectively. Notably, the lowest hydrogen generation current efficiency of 36.33% and % STH efficiency of 5.36% were obtained when Pt metal was used as both anode and cathode in Pt‖Pt electrochemical cell.

In Search of Efficient Anode and Cathode Materials for Double Junction Amorphous Silicon Solar Cell Driven all Solar Electrolysis of Water to Hydrogen and Oxygen Gases

INTRODUCTION The best way to produce pure hydrogen is by electrolysis and photoelectrolysis of water. Much research activities are in progress for direct photoelectrolysis of water . For the solar cell driven electrolysis of water to be cost effective the solar cells must be efficient, low cost and most importantly the anode and cathode materials should be also cost effective and non-noble metal based. In this work we report the hydrogen generation current, hydrogen current efficiency and the photoconversion efficiency of combination of few anode and cathode materials for water electrolysis driven by double junction amorphous silicon solar cells (DJ-a-Si). Amorphous Si solar cells are more cost effective compared to single crystalline Si solar cells. In this study three different anode materials (Co-Cr, Co-Cr-RuO2, and Ti-RuO2) and cathodes (Pt, Ni, and Cu) were tested for water splitting in an electrolyzer biased by double junction a-Si solar cell.

Enhanced Photoresponse of Hydrogen-Modified (HM)-n-TiO2 for Water Splitting Reaction

INTRODUCTION The most studied semiconductor for water splitting reaction to H2 and O2 is n-TiO2 because of its long-term chemical stability against the harsh chemical environment in the acidic or basic electrolyte solutions, non-toxicity, and relatively low cost. On the other hand a serious disadvantage is that only the UV light which consists of 4% (300-400nm) of the solar irradiation can activate n-TiO2 due to its intrinsic band gap (3 eV(414nm) for Rutile and 3.2 eV (387nm) for anatase). Shifting the photosensitivity of the n-TiO2 to the visible light (400nm ≤ λ ≤ 750nm) and therefore better efficiency and possible marketability, is the most important challenge for the scientists within this domain. Several attempts and techniques have been made to lower the band-gap energy and shift the sensitivity of n-TiO2 to the visible light (λ = 400 nm -750 nm) by doping with transition metals , nonmetal dopants such as sulfur, nitrogen, and carbon 4, 5 or reduction under hydrogen ambient. 7 The (HM)-n-TiO2 (hydrogen modified nTiO2) was reported in 1953 by Breckenridge et al in an attempt to increase the conductivity of TiO2 semiconductor, the absorbance of visible light was increased after reducing TiO2 rutile at high temperature in hydrogen ambient. In the present study, we reported a new method for the synthesis of hydrogen modified (HM)-n-TiO2 thin films by thermal oxidation of Ti metal sheet to TiO2 followed incorporation of hydrogen in it by by electrochemical reduced in a alkaline medium .