Hsu, Y.-K.Y.-K.HsuChen, Y.-C.Y.-C.ChenLin, Y.-G.Y.-G.LinChen, L.-C.L.-C.ChenChen, K.-H.K.-H.Chen2020-06-182020-06-18201209599428https://scholars.lib.ntu.edu.tw/handle/123456789/503286A cost-effective and simple electroplating technique has been developed to prepare layered manganese oxide (MnO 2) arrays as a promising material for solar hydrogen production and waste-water cleaning through photoelectrochemical (PEC) process. The microstructure of these MnO 2 nanosheets can be referenced to Birnessite-type, as characterized by Raman spectra and transmission electron microscopy. The bandgap energy of the as-grown nanosheets determined from UV-vis spectroscopy is about 2.1 eV. Mott-Schottky plots show the flat band potential of the MnO 2 nanosheets to be -0.01 V and a donor concentration of 4.68 × 10 20 cm -3. Remarkable photocurrent in response to visible light is observed in the presence of hole acceptors, such as sodium formate and methanol, which efficiently suppress the recombination loss of electron-hole pairs from localized d-d transitions within manganese ion. Meanwhile, the transient photocurrent-time responses and the effect of different hole acceptors on PEC activity are studied with an increase of respective hole acceptor concentration, and the results reveal the critical role in the process of absorption and decomposition of the hole acceptor. Significantly, the MnO 2 nanosheets exhibit an incident photon-to-electron conversion efficiency of 7% in response to the monochromatic wavelength of 400 nm, which is comparable to that from hematite (α-Fe 2O 3). These results demonstrate the nanoporous MnO 2 nanosheets have great potential in solar hydrogen applications and organic pollutant cleaning. © 2012 The Royal Society of Chemistry.[SDGs]SDG7Acceptor concentrations; As-grown; Band gap energy; D-d transitions; Donor concentrations; Electron hole pairs; Electroplating technique; Flat band potential; Layered manganese oxide; Manganese ions; Monochromatic wavelength; Mott-Schottky plots; Nano-porous; Photoelectrochemicals; Recombination loss; Solar hydrogen; Solar Hydrogen Production; UV-vis spectroscopy; Visible light; Conversion efficiency; Electrochemistry; Electroplating; Hole concentration; Hydrogen; Hydrogen production; Iron ores; Light; Manganese; Methanol; Nanosheets; Organic pollutants; Oxides; Solar power generation; Transmission electron microscopy; Ultraviolet spectroscopy; Ultraviolet visible spectroscopy; Wastewater; Manganese oxidejournal article10.1039/c1jm14355g