Enhancing photoelectrochemical water splitting by combining work function tuning and heterojunction engineering

Abstract

We herein demonstrate the unusual effectiveness of two strategies in combination to enhance photoelectrochemical water splitting. First, the work function adjustment via molybdenum (Mo) doping significantly reduces the interfacial energy loss and increases the open-circuit photovoltage of bismuth vanadate (BiVO 4 ) photoelectrochemical cells. Second, the creation and optimization of the heterojunction of boron (B) doping carbon nitride (C 3 N 4 ) and Mo doping BiVO 4 to enforce directional charge transfer, accomplished by work function adjustment via B doping for C 3 N 4 , substantially boost the charge separation of photo-generated electron-hole pairs at the B-C 3 N 4 and Mo-BiVO 4 interface. The synergy between the above efforts have significantly reduced the onset potential, and enhanced charge separation and optical properties of the BiVO 4 -based photoanode, culminating in achieving a record applied bias photon-to-current efficiency of 2.67% at 0.54 V vs. the reversible hydrogen electrode. This work sheds light on designing and fabricating the semiconductor structures for the next-generation photoelectrodes.

Nanostructured core–shell metal borides–oxides as highly efficient electrocatalysts for photoelectrochemical water oxidation

“…6b). 4 It implies the upward band bending nature of the electrode in equilibrium with the electrolyte in dark. 43 In contrast, a moderate OCV light under illumination suggests the flattened band induced by photoexcited carrier.…”

“…43 By the introduction of MB catalysts, the E f shifts more positively compared to pristine photoanode, due to the mitigated E f pinning effect by passivating surface trapping states. 4 Therefore, a upgraded OCP value is achieved after coupling MB to WO 3 photoanodes. 4,43 It is noteworthy that in the OCV measurements the catalytic and kinetic impacts can be excluded, because within the system the current originating from the hypothetic redox reactions does not pass steadily.…”

“…4 Therefore, a upgraded OCP value is achieved after coupling MB to WO 3 photoanodes. 4,43 It is noteworthy that in the OCV measurements the catalytic and kinetic impacts can be excluded, because within the system the current originating from the hypothetic redox reactions does not pass steadily. 43 Meanwhile, the Ar atmosphere also prevented the measurements being interfered from the surface states passivation by dissolved-O 2 absorption.…”

“…2,3 PEC water splitting is considered as a sustainable solution to directly produce hydrogen from water using solar fuel. 4,5 To date, significant improvement has been achieved for photocathodes; profiting highly from the experiences in industrial semiconductor production technology such as solar cell development. 6,7 Nevertheless, water oxidation involving the transfer of four electrons is demanding with respect to kinetics and stability, thus limiting the PEC watersplitting efficiency.…”

Tailoring the Surface Properties of Bi2O2NCN by in Situ Activation for Augmented Photoelectrochemical Water Oxidation on WO3 and CuWO4 Heterojunction Photoanodes

“… 1 , 2 To this end, harnessing solar energy through energy conversion technologies represents a promising piece of the puzzle. 2 − 7 One such pathway uses PEC cells to obtain hydrogen from water upon solar illumination. 7 − 10 Photochemical water-splitting includes the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), which have to be accomplished simultaneously.…”