Fabrication of Thylakoid Membrane-Based Photo-Bioelectrochemical Bioanode for Self-Powered Light-Driven Electronics

Abstract

The transition toward sustainable and decentralized energy solutions necessitates the development of innovative bioelectronic systems capable of harvesting and converting renewable energy. Here, we present a novel photo-bioelectrochemical fuel cell architecture based on a biohybrid anode integrating laser-induced graphene (LIG), poly(3,4-ethylenedioxythiophene) (PEDOT), and isolated thylakoid membranes. LIG provided a porous, conductive scaffold, while PEDOT enhanced electrode compatibility, electrical conductivity, and operational stability. Compared to MXene-based systems that involve complex, multi-step synthesis, PEDOT offers a cost-effective and scalable alternative for bioelectrode fabrication. Thylakoid membranes were immobilized onto the PEDOT-modified LIG surface to enable light-driven electron generation. Electrochemical characterization revealed enhanced redox activity following PEDOT modification and stable photocurrent generation under light illumination, achieving a photocurrent density of approximately 18 µA cm⁻². The assembled photo-bioelectrochemical fuel cell employing a gas diffusion platinum cathode demonstrated an open-circuit voltage of 0.57 V and a peak power density of 36 µW cm⁻² in 0.1 M citrate buffer (pH 5.5) under light conditions. Furthermore, the integration of a charge pump circuit successfully boosted the harvested voltage to drive a low-power light-emitting diode, showcasing the practical viability of the system. This work highlights the potential of combining biological photosystems with conductive nanomaterials for the development of self-powered, light-driven bioelectronic devices.

1. Introduction

Decentralized and solar-driven technologies are emerging as pivotal strategies for promoting energy security and environmental sustainability [1,2]. In pursuit of efficient solar-to-electricity conversion, significant research efforts have been directed toward the development of photo-bioelectrochemical fuel cells, which leverage natural photosynthetic components such as Photosystem I (PSI) [3] and Photosystem II (PSII) [4] to harvest and convert light energy into electrical energy. These complexes (PSI and PSII) are challenging to isolate and often exhibit lower stability compared to the entire thylakoid membranes (TMs) due to the disruption of their natural macro-organization and supporting lipid environment [5]. In contrast, TMs, which contain a full complement of photosynthetic pigments, proteins, and lipids, provide a more stable and efficient platform capable of sustaining the conversion of chemical energy into electrical energy [6]. The natural structure of TMs supports efficient energy transfer and electron flow, improving photosynthetic performance [7].

In addition, TMs present distinct advantages over synthetic photoactive materials, owing to their highly organized protein complexes (PSI and PSII) that enable efficient light absorption and near-unity quantum yield [8]. Their broad-spectrum pigment composition (chlorophylls and carotenoids) supports full visible light harvesting [9], while the integrated electron transport chain ensures mediator-free, directional charge flow. They are environmentally benign and biodegradable, thereby enabling thylakoids to avoid the toxicity associated with heavy-metal-based materials [10] and maintain structural stability in aqueous, mildly acidic environments [11]. Notably, their inherent capacity for self-regulation and repair under stress (e.g., photoinhibition and temperature shifts) imparts resilience absent in most artificial systems [12]. These features highlight the potential of thylakoid membranes as robust, sustainable photoactive platforms for biohybrid and energy-harvesting applications.

However, realizing efficient electron transfer from TMs to solid-state electrodes remains a central challenge, primarily due to limited bioelectrode interface contact, poor membrane adhesion, and high charge transfer resistance. Significant efforts have been directed toward improving the bioelectronic interface in TM-based photo-biofuel cells. Chang et al. demonstrated that the osmotic expansion of thylakoids enhanced membranes on gold electrodes, yielding improved charge transport and a photocurrent density of 214 ± 8 nA cm⁻², with a corresponding peak power density of 0.49 μW cm⁻² [13]. To enable direct electron transfer (DET) without reliance on redox mediators, Yun et al. employed mussel-adhesive protein-coated carbon nanotubes to create a conductive percolation network within TM composites [14]. The system produced a photocurrent of 4.25 µA cm⁻², demonstrating the importance of conductive nanomaterials in bioelectrode design. Emphasizing scalability and device flexibility, Son et al. implemented inkjet-printed carbon nanotubes (CNTs) in conjunction with osmotically shocked thylakoids on paper substrates, yielding a soft and lightweight device with a photocurrent of 480 nA cm⁻² and a power output of 250 µW cm⁻², over 22-fold higher than comparable alga-based platforms.

Electrode surface modification has also proven effective for enhancing charge extraction [15]. Hong et al. utilized RuO₂ nanosheet-modified electrodes to promote electrostatic interactions and the ensemble docking of TMs [16]. This configuration generated a photocurrent of 500 nA and demonstrated real-world viability by powering a calculator using an eight-cell stacked array. Recently, Sarode et al. reported a high-performance bioanode based on MXene-decorated laser-induced graphene (LIG) [17]. The synergistic effect between MXene’s high conductivity and LIG’s hierarchical porosity led to a remarkable photocurrent density of 29.18 µA cm⁻² and a peak power density of 7.24 µW cm⁻², representing one of the highest reported performances for TM-based photo-biofuel cells to date.

Conductive nanomaterials such as CNTs and graphene oxide (GO) have significantly enhanced DET, with CNTs forming percolative networks and GO increasing surface area and interfacial conductivity, leading to improved photocurrents and power output [18,19]. Redox mediators like ferricyanide and osmium complexes and polymers like alginate hydrogels and chitosan have been explored as alternative pathways to facilitate charge transfer and preserve TM activity, respectively, under dynamic lighting, thereby improving operational stability [20,21,22,23,24,25]. The integration of conductive polymers, particularly poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), has emerged as a promising strategy to enhance the performance of thylakoid-based biofuel cells [26,27,28,29,30,31]. PEDOT:PSS offers a biocompatible, highly conductive matrix that supports stable thylakoid immobilization while promoting efficient electron extraction. Qi et al. demonstrated that blending PEDOT:PSS with thylakoids in a 3D-printed bioelectrode significantly improved charge transfer, yielding a photocurrent density of 55.3 μA cm⁻² and a power density of 6.5 μW cm⁻² under illumination [32].

Additionally, LIG has emerged as a promising material for bioelectronic platforms due to its low-cost, environmentally benign fabrication, and unique combination of high porosity, electrical conductivity, and mechanical stability [33,34,35]. Recent advances in TM-based biofuel cells have highlighted the synergistic benefits of coupling TMs with carbon nanomaterials. For instance, Pankratova et al. functionalized 3D graphene matrices with aminoaryl groups, enabling oriented TM immobilization and achieving mediator-free photocurrents of 5.24 ± 0.50 µA cm⁻² [36]. Similarly, Hamidi et al. utilized osmium polymer-modified graphite electrodes to attain a photocurrent of 42.4 µA cm⁻², demonstrating the efficacy of redox-active carbon interfaces for photosynthetic energy harvesting [37]. Bunea et al. further improved scalability by developing micropatterned carbon-on-quartz electrodes with enhanced surface area and transparency, supporting larger TM loads and efficient backside illumination [38].

Despite these advances, the need remains for biohybrid electrode platforms that combine low-cost fabrication, structural adaptability, biocompatibility, and efficient photoelectrochemical performance. Unlike MXene-based systems that require complex synthesis, inert conditions, and stability control [17], our approach leverages PEDOT, a commercially available, solution-processable polymer, electrodeposited under ambient conditions. This streamlines fabrication, lowers costs, and improves stability in aqueous environments. Combined with drop-casting for thylakoid immobilization, the process avoids high-temperature or vacuum steps, supporting scalable integration into wearable, biosensing, and sustainable energy applications.

In this context, we present a novel TM-integrated photo-electrochemical fuel cell based on PEDOT-modified LIG electrodes. This architecture leverages the high surface area and conductivity of LIG, the electrochemical stability of PEDOT, and the light-harvesting capability of TMs to achieve enhanced photocurrent generation and energy conversion. The performance, stability, and real-world applicability of the system are systematically investigated, offering a new paradigm for the design of scalable, light-responsive bioelectronic devices. To construct a complete photoelectrochemical system, the resulting photoanode was integrated with a gas diffusion-based platinum electrode as the cathode. Utilizing a charge pump circuit, the system successfully harvested and managed the generated photocurrent to power an ultralow-powered light-emitting diode (LED). This showcases the practical proof-of-concept demonstration of the proposed energy-harvesting system, thereby demonstrating a promising strategy for combining biohybrid materials with microelectronic components to achieve efficient solar-to-electric energy conversion at small scales.

2. Materials and Methods

2.1. Materials

Citric acid anhydrous (C₆H₈O₇, ≥99.5%) and sodium phosphate monobasic (NaH₂PO₄) were purchased from Fisher Scientific (Waltham, MA, USA), and sodium hydroxide (NaOH, ≥97.0%) and sodium citrate dihydrate from fisher chemical. Lithium perchlorate (LiClO₄, ≥95.0%), 3,4-ethylenedioxythiophene (C₆H₆O₂S, 97%), potassium chloride (KCl, 99.0%), magnesium chloride (MgCl₂, ≥98.0%), sodium phosphate dibasic, sodium chloride (NaCl, 99.5%), potassium phosphate monobasic, (≥99.0%), and potassium ferricyanide (K₃[Fe(CN)₆], 99%) were purchased from Sigma (St. Louis, MI, USA), and sucrose (C₁₂H₂₂O₁₁, ≥99.0%) and tricine (C₆H₁₃NO₅, 99+%) from ThermoScientific (Waltham, MA, USA). Pyralux^® LF copper-clad laminate was sourced from DuPont, Inc. (Wilmington, DE, USA), while platinum-based gas diffusion electrodes (GDEs) were procured from the Fuel Cell Store (Bryan, TX, USA). The developed electrodes were characterized by field-emission scanning electron microscopy (FESEM; Hitachi SU-8000, Schaumburg, IL, USA). All solutions were prepared using Milli-Q water (ThermoScientific, Waltham, MA, USA) with a resistivity of at least 18 MΩ·cm.

2.2. Thylakoid Extraction from Spinach

Thylakoids were extracted from organic Spinacia oleracea following established procedures [14,17,39]. Fresh spinach leaves were thoroughly washed, dried, and blended, and the resulting mixture was filtered through a 20 µm nylon mesh. Solid debris in the filtered solution was removed by centrifugation at 2000× g for intermediate steps and at 4000 rpm during the final ultracentrifugation step using a benchtop centrifuge (J-15R, Beckman Coulter Inc., Brea, CA, USA). The chloroplasts were lysed by osmotic shock through their transfer into a 10 mM MgCl₂ solution, facilitating the release of thylakoid membranes. The membranes were subsequently isolated by centrifugation with intermediate steps performed at 2000× g and final ultracentrifugation carried out at 4000 rpm, before being stored in a 50 mM phosphate buffer for future use. The total chlorophyll concentration of the thylakoids was determined spectrophotometrically according to previously reported methods [40].

2.3. Fabrication of the Photoanode Electrode

Figure 1A illustrates the fabrication of the laser-induced graphene (LIG) electrodes by direct laser scribing on a commercial Pyralux^® polyimide sheet. During scribing, the CO₂ laser power was set at 20% of the maximum and the printing speed was maintained at 200 mm/s, while operating at a wavelength of 10.6 µm. Graphene was synthesized on the polyimide (PI) side of the Pyralux^® sheet, while the opposite copper side was passivated by applying a layer of liquid electrical tape to prevent unwanted electrical contact. Additionally, PI tape was used to selectively mask specific regions to define the electroactive working area. PEDOT was deposited onto the working area of the LIG electrode using a three-electrode setup illustrated in Figure 1B. The LIG served as the working electrode (WE), a platinum wire as the counter electrode (CE), and a Ag/AgCl electrode as the reference (RE), all connected to a potentiostat. The electrolyte was prepared by dissolving 10.68 µL of pure EDOT in 10 mL of 0.1 M LiClO₄ solution to achieve a 10 mM concentration. PEDOT was electrodeposited by chronoamperometry at +1.2 V versus Ag/AgCl for 60 s. Figure 1C shows the drop-casting of the isolated TMs onto the PEDOT-modified LIG surface, resulting in the final photoanode structure. This biohybrid electrode was engineered to enhance photoelectrochemical performance by combining the high conductivity of LIG, the electroactive properties of PEDOT, and the photosynthetic functionality of thylakoid membranes.

2.4. Electrochemical Characterization

Electrochemical measurements were performed using a PalmSens4 potentiostat (PalmSens, Houten, The Netherlands) using a three-electrode configuration for cyclic voltammetry (CV) and two-electrode configuration for linear sweep voltammetry (LSV). CV and chronoamperometry (CA) experiments were conducted in a 0.1 M citrate buffer at pH 5.5. The choice of 0.1 M citrate buffer at pH 5.5 is based on well-established research showing that this pH closely resembles the physiological lumenal pH of chloroplasts (5.1–5.7), helping to maintain protein structure and enhance the stability of electron transfer components like PSI and PSII. Previous studies have consistently used pH 5.5 for thylakoid-based electrodes, citing the significant loss of performance outside this range [17,41,42]. Therefore, this buffer condition was selected to ensure reproducibility, system stability, and biological compatibility. The electrochemical behavior of the LIG/PEDOT electrode was further characterized by CV using a 5 mM potassium ferricyanide solution, with potentials swept between −0.4 V and 0.8 V at scan rates ranging from 10 mV/s to 100 mV/s. For the photo-bioelectrochemical fuel cell evaluation, LSV was employed at a scan rate of 1 mV/s to generate polarization curves, where the LIG/PEDOT/Thylakoid photoanode was used as the working electrode and a platinum-based gas diffusion electrode functioned as the cathode.

3. Results and Discussion

3.1. Morphological Characterization of Laser-Induced Graphene Surface Modification

Figure 2 presents the scanning electron microscopy (SEM) micrographs highlighting the morphological evolution of the electrode surfaces at a magnification scale of 5 µm. Figure 2a shows the surface of the bare LIG, which exhibits a highly porous, three-dimensional interconnected network typical of laser-scribed carbon structures [43,44,45]. This porous morphology provides a large surface area beneficial for subsequent material modifications. Figure 2b displays the LIG electrode after the electrodeposition of PEDOT, where a noticeable change in the surface texture is observed. The PEDOT coating forms an irregular, rough layer over the porous graphene framework, indicating successful polymer deposition while maintaining the underlying porosity crucial for effective mass transport. Figure 2c shows the LIG/PEDOT surface following the drop-casting of TMs. A denser and more compact structure is observed, suggesting the effective immobilization of biological material onto the PEDOT-modified surface. The thylakoid layer appears to integrate well with the underlying substrate, which is expected to facilitate efficient photoinduced electron transfer in the photoanode.

3.2. Electrochemical Characterizations of LIG/PEDOT Electrode

To evaluate the electrochemical performance of the PEDOT-modified LIG electrode (LIG/PEDOT), CV analyses were performed. Figure 3a displays CV curves for both the bare LIG electrode (black curve) and the LIG/PEDOT electrode (red dotted and dashed curve), scanned from −0.4 to 0.8 V at a scan rate of 20 mV/s in a 5 mM K₃[Fe(CN)₆] solution containing 0.1 M KCl. The bare LIG electrode exhibited distinct redox peaks with an oxidation peak current (I_a) of approximately 90 µA. Upon modification with PEDOT, the oxidation peak current increased to approximately 108 µA, indicating enhanced electrochemical activity due to the improved conductivity and redox properties imparted by the PEDOT layer. This improvement is attributed to the increased effective surface area and superior charge transport properties provided by the PEDOT coating, facilitating faster electron transfer between the electrode surface and the redox species.

To optimize PEDOT film formation, electrodeposition was conducted at +1.2 V vs. Ag/AgCl. The selected potential is supported by Balamurugan and Chen, who demonstrated that the potential window (+1.0 to +1.5 V) with +1.2 V yields uniform, stable, and electroactive PEDOT films suitable for electrochemical applications [46]. The optimization of deposition time was evaluated via CV (Figure S1, Supplementary Information), with curves (i)–(iv) corresponding to 0 s (bare LIG), 30 s, 60 s, and 90 s. Progressive increases in anodic and cathodic peak currents confirmed enhanced redox activity with extended deposition. A 60 s deposition time was selected for subsequent experiments, as it provided an optimal balance between electrochemical performance, film uniformity, and structural stability.

Further investigation of the LIG/PEDOT electrode’s behavior at varying scan rates (10–100 mV/s) is shown in Figure 3b. A systematic increase in peak currents with increasing scan rate was observed, confirming the electroactive nature of the PEDOT layer. Figure 3c shows a linear relationship between the anodic (I_a) and cathodic (I_c) peak currents and the square root of the scan rate, with correlation coefficients (r²) of 0.9800 and 0.9841, respectively. This linear dependence suggests that the electrochemical process is diffusion-controlled. The effective electrochemical surface areas (A) of the bare LIG and LIG/PEDOT electrodes were further estimated using the Randles–Sevcik equation:

$$I_p=\left(2.69\times {10}^5\right)n^{1.5}{D}^{0.5}C{AV}^{0.5}$$

(1)

where I_p is the peak current, n is the number of electrons transferred for Fe(CN)₆³⁻/Fe(CN)₆⁴⁻, D is the diffusion coefficient (7.6 × 10⁻⁶ cm²/s), C is the concentration of the redox species (5 mM), A is the effective surface area (cm²), and v is the scan rate (V/s). Based on the calculations, the effective electrochemical surface area of the bare LIG electrode was determined to be approximately 0.058 cm², whereas the LIG/PEDOT electrode exhibited an increased surface area of about 0.066 cm². This enhancement further supports the conclusion that PEDOT modification improves the electrochemical performance of the LIG electrode by increasing the active area available for redox reactions.

The photoelectrochemical behavior of the LIG/PEDOT/Thylakoid bioanode was further evaluated under dark and illuminated conditions. As shown in Figure 4a, the CV measurements were performed in a 0.1 M citrate buffer solution (pH 5.5) at a scan rate of 100 mV/s. Under dark conditions (black curve), the LIG/PEDOT/Thylakoid bioanode exhibited minimal redox activity. Upon illumination (red curve), a noticeable enhancement in the anodic peak current was observed, as highlighted in the inset, indicating efficient light-induced charge separation and electron transfer facilitated by the photosynthetic TMs. To further confirm the light responsiveness, chronoamperometry measurements were conducted under light illumination conditions (Figure 4b). The LIG/PEDOT/Thylakoid bioanode (black curve) exhibited distinct photocurrent generation, achieving a stable photocurrent density of approximately 18 µA cm⁻² under illumination, with rapid and stable current responses corresponding to light on/off cycles. In contrast, the light-off condition (red curve) exhibited negligible current change, confirming that the photocurrent arises from the photoactivity of the thylakoid membranes integrated onto the LIG/PEDOT substrate.

The operational stability of the LIG/PEDOT/Thylakoid bioanode was evaluated under prolonged illumination. As shown in Figure S2 (Supplementary Information), the electrode maintained a stable and reproducible photocurrent over 20 light ON/OFF cycles during a 1 h chronoamperometric test at +0.6 V vs. Ag/AgCl in 0.1 M citrate buffer (pH 5.5). The minimal decline in photocurrent suggests good photoelectrochemical stability and reversibility of the thylakoid components. Slight decreases in activity are likely due to photoinduced stress or the partial deactivation of photosynthetic proteins, which are common limitations in biohybrid systems. Nonetheless, the system preserved a substantial portion of its initial activity, confirming the robustness and durability of the bioanode under operational conditions. These results highlight the practical potential of thylakoid-integrated electrodes for sustainable energy applications.

3.3. Characterization of LIG/PEDOT/Thylakoid Bioanode-Based Fuel Cell

Furthermore, the photo-bioelectrochemical fuel cell performance was evaluated under illumination in a 0.1 M citrate buffer solution (pH 5.5). The polarization and power density curves are shown in Figure 5. The cell exhibited an open-circuit voltage (OCV) of approximately 0.57 V, highlighting the efficient photoinduced charge separation provided by the integrated TMs. Upon increasing the current density, the cell voltage gradually decreased due to internal resistance and charge transport limitations. A maximum power density of approximately 36 µW cm⁻² was achieved at an optimal current density of approximately 230 µA cm⁻². The calculated energy conversion efficiency of the system was approximately 30.4% under an illumination intensity of 0.106 mW cm⁻². This enhanced performance demonstrates the successful coupling of the highly conductive LIG/PEDOT matrix with biologically active TMs, enabling effective light energy conversion into electrical energy.

The enhancement in photocurrent and power output observed for the LIG/PEDOT/Thylakoid photoanode arises from the synergistic integration of two complementary conductive layers. LIG provides a highly porous, three-dimensional carbon network with excellent in-plane electron mobility, which supports efficient charge collection over a large electroactive surface area. Meanwhile, PEDOT, a redox-active, solution-processable conductive polymer, forms a conformal coating over the LIG, creating a bio-interfacing layer that facilitates intimate contact with the immobilized thylakoid membranes. PEDOT acts as both an electron mediator and a stabilizing matrix, promoting the efficient extraction of photogenerated electrons from PSI and PSII embedded in the thylakoid membranes. These electrons are then transferred through the PEDOT matrix and swiftly delivered via the underlying LIG scaffold to the external circuit. This hierarchical architecture minimizes interfacial resistance, suppresses charge recombination, and enables efficient charge separation and transport. The resulting improvement in photo-bioelectrochemical performance highlights the advantage of combining nanostructured carbon frameworks with conductive polymers in the design of biohybrid photoanodes for sustainable energy harvesting.

The practical applicability of the fabricated LIG/PEDOT/Thylakoid-based photo-bioelectrochemical fuel cell was demonstrated via the integration of a voltage-boosting circuit, a low-input voltage charge pump integrated circuit (IC: S-882Z), as illustrated in Figure 6a. The photo-bioelectrochemical fuel cell generated a sufficient open-circuit voltage (OCV) of 0.57 V under illumination to serve as the input for the charge pump circuit (Vin = 0.270 V). The boosted output voltage of approximately 1.8 V successfully powered a low-power red LED, confirming the ability of the system to harvest light energy and drive small electronic loads. Figure 6b shows the LED during the charging phase (OFF state), and Figure 6c shows the illuminated LED in the ON state. This approach is analogous to previously reported strategies where biofuel cell-generated voltages, although inherently low, were amplified using charge pump ICs to enable device operation [47,48,49].

In the representative demonstration, light absorption by the thylakoid bioanode initiated electron transfer, leading to charge accumulation via the integrated charge pump. This process culminated in a burst of light from the LED, occurring approximately three seconds after initial illumination. The delayed activation of the LED reflects the transient nature of power generation in such biohybrid systems, where instantaneous current output is inherently limited by the kinetics of the biological electron transport chain. Additionally, this pulsed behavior exemplifies a key characteristic of charge pump circuit, namely, the capacity for intermittent yet reproducible power output, suitable for low-power microelectronic applications. The successful triggering of the LED not only highlights the feasibility of coupling photosynthetic bioelectrodes with downstream circuitry but also validates the functional integration of biological and electronic components, thereby demonstrating a viable pathway for developing self-powered bioelectronic systems capable of functioning under sustainable, light-driven conditions without external power sources.

The performance of the LIG/PEDOT/Thylakoid-based photo-bioelectrochemical fuel cell is compared with previously reported thylakoid-based fuel cell systems in

Table 1. Comparison of photocurrent densities achieved by various thylakoid-based photoanodes.

No	Photoanode	OCV	Photocurrent	Power Density	Ref.
1	Au/Expanded TM Au/stacked TM	220 mV 190 mV	214 nA cm−2 191 nA cm−2	--	[13]
2	LIG/MXene/Thylakoid	450 mV	29.18 µA cm−2	7.24 µW cm−2	[17]
3	GC/rGO/Thylakoid	500 mV	5.24 µA cm−2	1.79 μW cm−2	[36]
4	Carbon Paper/ Stroma Thylakoid	--	51 ± 4 nA cm−2	0.65 nW cm−2	[42]
5	Thylakoid-Deposited Micro-Pillar Electrodes	407 mV	280 nA cm−2	64 nW cm−2	[50]
6	Glassy Carbon/Thylakoid Monolayer	--	230 nA cm−2	--	[51]
7	Thylakoid/PFP Conducting Polymer	--	1246 nA cm−2	--	[52]
8	LIG/PEDOT/Thylakoid	570 mV	18 μA cm−2	36 µW cm−2	This work

. This summary highlights key performance metrics including open-circuit voltage (OCV), photocurrent density, and power density under illumination. The LIG/PEDOT/Thylakoid device achieved a photocurrent density of 18 μA cm⁻², a power density of 36 μW cm⁻², and a OCV of 570 mV, representing a substantial enhancement relative to most previously reported systems. This photocurrent output is over 60-fold higher than that of thylakoid-deposited micropillar electrodes (280 nA cm⁻²) [50] and nearly 80 times greater than monolayer TM systems immobilized on glassy carbon (230 nA cm⁻²) [51]. Compared to stacked or osmotically expanded TM architectures on gold electrodes, which achieved current densities of 191–214 nA cm⁻² and power densities below 0.5 μW cm⁻² [13], the current system demonstrates a significant improvement in both charge extraction and energy conversion.

Among the few high-performing systems, such as the LIG-MXene-TM hybrid, which reached 29.18 μA cm⁻² and 7.24 μW cm⁻² [17], and thylakoid/PFP conductive polymer composites that yielded 1246 ± 41 nA cm⁻² [52], the fabricated LIG/PEDOT/Thylakoid-based fuel cell offers competitive performance with additional benefits of simpler fabrication and mechanical flexibility. Additionally, the fabricated system outperforms the GC/rGO/TM interface reported by Pankratova et al. [36], which achieved 5.24 ± 0.50 μA cm⁻² and 1.79 ± 0.19 μW cm⁻². The enhanced performance of the fabricated system can be attributed to the synergistic integration of LIG with the conductive polymer PEDOT, which creates a highly porous, conductive, and biocompatible scaffold for efficient thylakoid immobilization and charge transfer. The three-dimensional hierarchical architecture of LIG increases electroactive surface area, while PEDOT ensures stable electron conduction and interface compatibility with thylakoid membranes, thereby overcoming major challenges seen in earlier TM-based photoanodes, such as poor electron transfer, weak membrane attachment, and limited scalability. Further, this confirms that the fabricated LIG/PEDOT/Thylakoid photoanode is among the top-performing thylakoid bioelectrodes reported to date and represents a significant advancement toward practical, sustainable, and flexible photo-bioelectrochemical energy systems. The system’s demonstrated capability to power a charge pump and drive an LED highlights its potential for integration into low-power, self-sustained electronic devices. Unlike conventional bioelectrochemical platforms, this light-driven, fuel-free architecture offers simplified operation, enhanced environmental compatibility, and greater scalability. These attributes, coupled with its improved photo-bioelectrochemical performance, position the LIG/PEDOT/Thylakoid-based system as a promising candidate for next-generation sustainable energy-harvesting technologies.

4. Conclusions

The development of a novel photoanode architecture that integrates LIG, PEDOT, and TMs into a synergistic hybrid thylakoid-based photo-bioelectrochemical fuel cell was demonstrated. The resulting thylakoid-based photo-bioelectrochemical fuel cell demonstrated a photocurrent density of approximately 18 μA cm⁻², an OCV of 0.57 V, and a peak power density of 36 μW cm⁻² under illumination. These performance metrics position the fabricated thylakoid-based photo-bioelectrochemical fuel cell among the highest-performing TM-based photoelectrochemical systems reported to date, as evidenced by comparative benchmarking with state-of-the-art biohybrid platforms. The feasibility of real-world deployment was successfully demonstrated by coupling the thylakoid-based photo-bioelectrochemical fuel cell with a low-voltage charge pump circuit, which amplified the harvested voltage to levels sufficient for powering a low-power LED. This demonstration shows the system’s promise for powering biosensors, wearable electronics, and standalone environmental devices. Future work will focus on further optimizing long-term operational stability and integrating energy storage elements for continuous, off-grid operation.