Photosystem II for photoelectrochemical hydrogen production

Abstract

Water is a primary source of electrons and protons for photosynthetic organisms. For the production of hydrogen through the process of mimicking natural photosynthesis, photosystem II (PSII)-based hybrid photosynthetic systems have been created, both with and without an external voltage source. In the past 30 years, various PSII immobilization techniques have been proposed, and redox polymers have been created for charge transfer from PSII. This review considers the main components of photosynthetic systems, methods for evaluating efficiency, implemented systems and the ways to improve them. Recently, low-overpotential catalysts have emerged that do not contain precious metals, which could ultimately replace Pt and Ir catalysts and make water electrolysis cheaper. However, PSII competes with semiconductor analogues that are less efficient but more stable. Methods originally created for sensors also allow for the use of PSII as a component of a photoanode. To date, charge transfer from PSII remains a bottleneck for such systems. Novel data about action mechanism of artificial electron acceptors in PSII could develop redox polymers to level out mass transport limitations. Hydrogen-producing systems based on PSII have allowed to work out processes in artificial photosynthesis, investigate its features and limitations.

Supplementary information: The online version contains supplementary material available at 10.1007/s12551-023-01139-5.

Keywords: Hydrogen evolution reaction; Hydrogenase immobilization; Photosystem II immobilization; Redox polymers; Semi-artificial photosynthesis; Water-splitting.

Fig. 1

Different configurations of SAPSS; photoelectrochemical water splitting (a–c): PSII wiring to HEC by (Mersch et al. 2015) external bias (a), immobilization of PSII on photoanode (Li et al. ; Sokol et al. 2018) (b), and immobilization of HEC on photocathode (Wang et al. 2016) (c). One bulk system (Wang et al. 2014) (d)

Fig. 2

Energy diagram of natural (left) and artificial (right) photosynthesis. The role of PQ can be played by its analogs XQ (DCBQ, DMBQ; or quinone wired to polymer chain); for long distance transfer, P_Os could be used. Approximately 1 V is needed to force electron transfer from the redox polymer to the hydrogenase, which can be applied by bias or PSI analogs: semiconductors with bands > 1 V (Wang et al. ; Li et al. ; Wang et al. 2014) or sensitized semiconductors (Rao et al. ; Sokol et al. 2018) such as TiO₂

Fig. 3

Immobilization techniques: a Ni-NTA binding with BSA spacers (Maly et al. 2005a), b 1-octanethiol and [16-mercaptohexadecanoic acid -Ni-NTA] (100 : 1 is optimal ratio) binds CPHis43 forming monolayers of PSII (Badura et al. 2006), and c covalent immobilization for DET (Kato et al. 2013); based on provided data

Fig. 4

Macroporous electrodes for increased loading of PSII: a scheme of macroporous electrode preparation; after evaporation of the matrix, pores are formed, which enables immobilization of enzyme complexes, membranes and whole cells. (Mersch et al. 2015). b Photocurrent densities of IO-ITO electrodes (based on (Sokol et al. 2016)) for flat, 20, 40, and 80-μm layers of IO-ITO.

Fig. 5

Progress in wiring PSII to electrodes. Dependence of turnover frequency on applied polymer (left chart): poly(1-vinylimidazole)-Os(bipy)₂Cl-polymer (Pos) (Sokol et al. 2016), poly(mercapto-p-benzoquinone) (pMBQ) (Yehezkeli et al. 2012), poly(bis-aniline) (PbANI) (Yehezkeli et al. 2012), poly lysine benzoquinone (pLBQ) (Yehezkeli et al. 2013), direct electron transfer from PSII (DET) (Sokol et al. 2016), polyethyleneglycolmethacrylat (PPhen) (Sokol et al. 2016), poly(1-vinylimidazole)-Os(bipy)₂Cl-polymer (Pos) modified with indium tin oxide nanoparticles (ITO) (Lee et al. 2021). Current density for different electrode designs (right chart): golden electrode modified with poly(1-vinylimidazole)-Os(bipy)₂Cl-polymer (Pos) (Badura et al. ; Hartmann et al. ; Wang et al. 2020), golden electrode modified with poly(mercapto-p-benzoquinone) (pMBQ) (Yehezkeli et al. 2012), golden electrode modified with poly(bis-aniline) (PbANI) (Yehezkeli et al. 2012), indium tin oxide (ITO) electrode modified with poly lysine benzoquinone (pLBQ) (Yehezkeli et al. 2013), direct electron transfer from PSII to inverse opal/indium tin oxide (IO-ITO) electrode (Sokol et al. 2016), inverse opal/indium tin oxide (IO-ITO) electrode modified with poly(1-vinylimidazole)-Os(bipy)₂Cl-polymer (Pos) (Sokol et al. 2016), inverse opal/indium tin oxide (IO-ITO) electrode modified with polyethyleneglycolmethacrylat (PPhen) (Sokol et al. 2016), indium tin oxide (ITO) electrode modified with polypyrrole p-benzoquinone (PPyBQ) (Li et al. 2017a), carbon paper modified with poly(fluorene-co-phenylene) (PFP) (Zeng et al. 2021), graphite electrode modified with poly(1-vinylimidazole)-Os(bipy)₂Cl-polymer (Pos) and indium tin oxide (ITO) nanoparticles (Lee et al. 2021) (Supplementary Table 1)

Fig. 6

Redox polymers on energy diagram vs. SHE and structural formula

Fig. 7

Bias-free hydrogen production with PSII-enriched membrane fragments (Li et al. 2017b) a scheme of cell: Pt is separated from PSII bulk by Nafion membrane, charge from PSII transfers to graphite electrode with DMBQ/DMBQH₂, FeCy is mediator between graphite and CdS surface. b Energy diagram of the cell