Interface Engineering of Hematite with Nacre-like Catalytic Multilayers for Solar Water Oxidation

Abstract

An efficient water oxidation photoanode based on hematite has been designed and fabricated by tailored assembly of graphene oxide (GO) nanosheets and cobalt polyoxometalate (Co-POM) water oxidation catalysts into a nacre-like multilayer architecture on a hematite photoanode. The deposition of catalytic multilayers provides a high photocatalytic efficiency and photoelectrochemical stability to underlying hematite photoanodes. Compared to the bare counterpart, the catalytic multilayer electrode exhibits a significantly higher photocurrent density and large cathodic shift in onset potential (∼369 mV) even at neutral pH conditions due to the improved charge transport and catalytic efficiency from the rational and precise assembly of GO and Co-POM. Unexpectedly, the polymeric base layer deposited prior to the catalytic multilayers improves the performance even more by facilitating the transfer of photogenerated holes for water oxidation through modification of the flat band potential of the underlying photoelectrode. This approach utilizing polymeric base and catalytic multilayers provides an insight into the design of highly efficient photoelectrodes and devices for artificial photosynthesis.

An Efficient Strategy for Boosting Photogenerated Charge Separation by Using Porphyrins as Interfacial Charge Mediators

“…[1][2][3][4] TheP EC process is mainly divided into three steps, [5][6][7][8][9] including adequate light harvesting,e ffective charge separation, and af ast surface reaction. [10,11] Unfortunately,many photocatalysts suffer from severe surface recombination [12] at the photoanode/electrolyte junction, which significantly hampers their application in photocatalytic and photoelectrocatalytic systems.Recently,b yl oading oxygen evolution cocatalysts (OECs), such as transition-metal (Fe, Co,N i) oxides and hydroxides (i.e., binary and ternary compounds), on the photoanodes (e.g.,n -Fe 2 O 3 , [13,14] n-BiVO 4 , [15] WO 3 [16] ), the PEC performance could be enhanced. [17] This enhancement could be due to improvement of the sluggish surface reaction kinetics (milliseconds-seconds)o ft he oxygen evolution reaction (OER) at the semiconductor/electrolyte (S-E) interface;t hat is,O ECs suppress electron-hole recombination at the photoanode/electrolyte junction by increasing the OER kinetics.…”

Polyoxometalates: Tailoring metal oxides in molecular dimension toward energy applications

“…351,352 Cobaltbased polyoxometalates have been applied to energy systems such as the redox couple in dye-sensitized solar cells. 43,349,[353][354][355][356][357][358][359] A number of other transition metalbased polyoxometalates have been investigated, such as silver-containing polyoxometalates, 226,[360][361][362][363][364][365] zinccontaining polyoxometalates. 366 polyoxotantalate, [367][368][369][370][371][372][373][374][375][376][377][378][379][380][381][382][383][384] ruthenium-containing polyoxometalates, [385][386][387] coppercontaining polyoxometalates, [388][389][390] chromium-containing polyoxometalates, 391 and polyoxoaurates [392][393]…”

Layer‐by‐Layer Assembly: Recent Progress from Layered Assemblies to Layered Nanoarchitectonics

“…2019, 14,2553 -2566 www.chemasianj.org cantly expanding the LbL toolkit. [77][78][79][80] Various organic compounds/GOhybrid materials have been createdbyusing physiochemical approaches, thereby improving the processability of these materials in different solvents and utilizing the outstanding properties of the attached molecules. [81] Aw ide range of organic compounds, including aromatic dyes, ionic liquids,a nd pyrene derivatives, have also been anchored onto GO nanosheets,either in ac ovalent or noncovalent manner, for applications in catalysis, electronic devices, and solar cells.…”

“…Unexpectedly,b esides the active layers,w ef ound that the base layer that is deposited prior to the catalytic multilayersa lso significantly influences catalytic activity.F or example, aw ater-oxidation photoanode was fabricated through the tailored assembly of GO nanosheets and ac obalt polyoxometalate catalysti nto an acre-like multilayer architecture on hematite. [80] When ab ase layer of a polyelectrolytec omplex was deposited onto the surface, a large shift in the flat-bandp otential was observed, owing to the creationo falocal dipole moment at the surface. As a result, the overall water-splitting reactionw as enhanced by tuning the band edge to amore favorable position for efficient charge separation.…”