Enhanced Photoelectrochemical Water Splitting of Black Silicon Photoanode with pH‐Dependent Copper‐Bipyridine Catalysts

Abstract

Since the water oxidation half‐reaction requires the transfer of multi‐electrons and the formation of O−O bond, it's crucial to investigate the catalytic behaviours of semiconductor photoanodes. In this work, a bio‐inspired copper‐bipyridine catalyst of Cu(dcbpy) is decorated on the nanoporous Si photoanode (black Si, b‐Si). Under AM1.5G illumination, the b‐Si/Cu(dcbpy) photoanode exhibits a high photocurrent density of 6.31 mA cm−2 at 1.5 VRHE at pH 11.0, which is dramatically improved from the b‐Si photoanode (1.03 mA cm−2) and f‐Si photoanode (0.0087 mA cm−2). Mechanism studies demonstrate that b‐Si/Cu(dcbpy) has improved light‐harvesting, interfacial charge‐transfer, and surface area for water splitting. More interestingly, b‐Si/Cu(dcbpy) exhibits a pH‐dependent water oxidation behaviour with a minimum Tafel slope of 241 mV/dec and the lowest overpotential of 0.19 V at pH 11.0, which is due to the monomer/dimer equilibrium of copper catalyst. At pH ∼11, the formation of dimeric hydroxyl‐complex could form O−O bond through a redox isomerization (RI) mechanism, which decreases the required potential for water oxidation. This in‐depth understanding of pH‐dependent water oxidation catalyst brings insights into the design of dimer water oxidation catalysts and efficient photoanodes for solar energy conversion.

Silicon photocathode functionalized with osmium complex catalyst for selective catalytic conversion of CO2 to methane

“…Si-based photocathode has advantages of element abundance, sunlight absorption, and high saturated photocurrent, as well as that its CB ideally straddles the required potential for CO 2 -to-CH 4 conversion 30 , 56 . Herein, a black Si photocathode with a nano-porous surface was prepared by a PEC HF etching method developed in our previous works 57 , 58 , which provides a large specific surface area for the deposition of abundant catalysts. Moreover, n-type TiO 2 layer was coated on the black Si surface by magnetron sputtering to form p-n heterojunction and protective layer, which can further improve the charge separation and stability of Si-based electrode 33 , 38 .…”

An assembled ternary photocatalyst CoPh/CdSe@TiO2 for simultaneous photocatalytic CO2and proton reduction

“…In this situation, CdSe QDs function as a photosensitizer, and the larger photocurrent of CdSe@TiO 2 demonstrates that the photoelectrons generated in CdSe QDs conduct through TiO 2 to the electrode. [43][44][45][46][47] The presence of TiO 2 enhances the charge separation in CdSe QDs and thus a larger photocurrent is generated. According to Mott-Schottky measurements (ESI, † Fig.…”

Regulating CO and H2 Ratios in Syngas Produced from Photocatalytic CO2/H2O Reduction by Cu and Co Dual Active Centers on Carbon Nitride Hollow Nanospheres

“…33−35 The very weak peaks at 778.8 and 794.9 eV can be attributed to Co 2p 3/2 and Co 2p 1/2 of the Co + species, suggesting the formation of Co(bpy) 2 + during the photoreaction. In the high-resolution Cu 2p XPS spectra (Figure S14d), in addition to the peaks at 934.9 and 955.0 eV ascribed to Cu 2+ and the satellite peaks at 942.5 and 962.9 eV, a set of peaks for Cu 2p 3/2 and Cu 2p 1/2 appear at 932.2 and 952.6 eV, 36,37 which can be attributed to Cu + species. These results further indicate that the Co and Cu complexes are successfully loaded on CNHS and the photogenerated electrons transfer from CNHS to the Cobpy and Cubpy complexes to form Co(bpy) 2 + and Cu(bpy) 2 + species during the photoreaction.…”