A New Porous Ni-W Mixed Metal Phosphonate Open Framework Material for Efficient Photoelectrochemical OER

Photoelectrochemical water oxidation or oxygen evolution reaction (PEC-OER) at the semiconductor surfaces has attracted huge attention over the years as it plays key role for energetically demanding processes like fuel cells, water splitting, and rechargeable metal-air batteries. Thus, development of sustainable, abundant and economical semiconductor nanomaterials as the catalyst for photoelectrochemical water oxidation reaction is very challenging in achieving high efficiency in the overall water splitting reaction. Herein, we report a new porous Ni-W mixed metal phosphonate material NiWPPA-4 with open framework structure through simple hydrothermal route and its crystalline framework has been indexed into a new orthorhombic crystal with unit cell dimensions: a=14.5506 angstrom, b=17.6445 angstrom, c=20.1766 angstrom and alpha=beta=gamma=90 degrees. NiWPPA-4 has been successfully utilized for photoelectrochemical OER from moderately basic medium [1(M) KOH] under constant irradiation of 100 mWcm(-1) light source. Semiconducting property together with nanoscale porosity in the Ni-W mixed metal phosphonate is responsible for photoelectrochemical OER in alkaline pH. To the best of our knowledge it is the first report on a mixed metal phosphonate material, which showed excellent catalytic activity in the photoelectrochemical OER. The onset-potential of NiWPPA-4 prepared over ITO coated glass was only -410 mV vs Ag/AgCl and the oxygen evolution rate is 275 mu mol g(-1). This study thus established efficient photoelectrochemical OER on porous mixed-metal phosphonates and offer opportunities for the utilization of metal phosphonates as potential photocatalyst in the energy conversion processes.