Enhanced Photoelectrochemical Water Splitting on Nickel‐Doped Cobalt Phosphate by Modulating both Charge Transfer and Oxygen Evolution Efficiencies

Abstract

Detrimental charge recombination at photoanode/electrolyte junctions severely impedes photoelectrochemical (PEC) performance. The deposition of cobalt phosphate (CoPi) onto photoanodes is an efficient approach to achieve high PEC efficiency. However, achieving performances at the required remains a huge challenge, owing to the passivation effect of CoPi. In this study, function‐tunable strategy, whereby the passivation role is switched with the activation role, is exploited to modulate PEC performance through simultaneous activation of interface charge transfer and surface catalysis. By depositing nickel‐doped CoPi onto a BiVO4 (BV) substrate, the integrated system (BV/Ni1Co7Pi) exhibits a remarkable photocurrent density (4.15 mA cm−2), which is a 4.6‐fold increase relative to BV (0.90 mA cm−2). Moreover, the satisfactory performance can be also achieved on α‐Fe2O3 photoanode. These findings provide guidance for improving the efficiency of CoPi on photoanodes for PEC water oxidation.

Insights into the Enhanced Photoelectrochemical Performance through Construction of the Z-Scheme and Type II Heterojunctions

“…To this end, transient photocurrent measurements ( I – t curves) were used to investigate the photogenerated charge carrier recombination. As illustrated in Figure d, the photocurrent density of BWO/BS/Au presents a “fast” decreasing trend, thus suggesting that severe interfacial charge recombination is also a major process. , More interestingly, once the Au NPs are inserted between BWO and BS, the photocurrent density of BWO/Au/BS exhibits a “slow” decreasing trend, proving that the new charge transfer pathway can suppress the recombination of accumulated holes with electrons, which is in excellent agreement with a previous report of such BVO photoanodes …”

“…48,49 More interestingly, once the Au NPs are inserted between BWO and BS, the photocurrent density of BWO/Au/BS exhibits a "slow" decreasing trend, proving that the new charge transfer pathway can suppress the recombination of accumulated holes with electrons, which is in excellent agreement with a previous report of such BVO photoanodes. 50 More precisely, the PEC efficiency (η) through PEC reaction is mainly determined by the product of the light absorption efficiency (η ab ), charge transfer efficiency (η ct ), and surface catalytic efficiency (η sc ). 51 The overlapped absorbance curves suggest that modulation of the charge transfer pathway through introduction of Au NPs has a light effect on light harvesting (Figure S10), revealing that the improved PEC performance can be ascribed to the following two processes, namely, charge transfer and surface catalysis.…”

MXene with controlled surface termination groups for boosting photoelectrochemical water splitting

“…11,12 Previously, most attention was paid to the engineering of the semiconductor/water interface by decorating the hole transport layer (HTL) and surface oxygen/hydrogen evolution catalysts, and a series of effective materials, such as metal/dimetal oxyhydroxides, borates, and phosphates, was well investigated to improve the PEC performance. [13][14][15] Nevertheless, another essential interface of the electrode/current collector through the introduction of the electron transport layer (ETL) is seriously undervalued. Currently, metal oxides, such as SnO 2 , TiO 2 , and WO 3 have been directly used as ETL to modulate the heterogeneous interface, however, the high resistance inevitably hinders the efficient transfer of photogenerated electrons.…”