Photoelectrochemical Stability Research Articles

Assessing the stability of binary copper oxide photocathodes and augmenting CuO water reduction performance: Comprehensive experimental and theoretical study

Using photocathodes such as Cu2O and CuO is an effective strategy for direct hydrogen production in photoelectrochemical (PEC) water splitting. The theoretical photocurrent densities of Cu2O and CuO are ∼14.7 and ∼35 mA cm−2, respectively, suggesting the superiority of CuO over Cu2O. However, the foremost drawback is the poor stability in aqueous solution under illumination. From this perspective, the PEC performance of CuO and Cu2O is compared via experimental and theoretical approaches. In this case, CuO outperformed Cu2O in terms of both PEC performance and stability, and the density functional theory (DFT) studies also evidently showed the same. Further, the AlOx and RuO2 were also loaded over CuO, and the CuO/AlOx/RuO2 delivered a photocurrent density of ∼2 mA cm−2 (@ +0.3 VRHE). The free energy plot shows the lower energy barrier of CuO/AlOx/RuO2 than CuO/AlOx and CuO, and it is present near and left side of the standard volcano plot, which further gives evidence for higher hydrogen evolution reaction (HER) performance.

Ion energy dependence of helium plasma irradiation effects on the photoelectrochemical properties of tungsten oxide

Abstract Tungsten samples with fuzz nanostructures on the surface were generated using helium plasma with different incident ion energies, and then fuzz tungsten oxide electrodes were prepared by calcination. The photoelectrochemical (PEC) properties and stability of the samples were measured, and the dependence on the incident ion energy was discussed. The mechanism of the fuzz structure to enhance the PEC performance of tungsten oxide was analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). The results show that fuzzy sample fabricated with higher ion energy has greater PEC performance, which is mainly caused by the increase in active surface area.

Origin of Enhanced Photoelectrochemical Activity of the n-CdS/p-type Semiconductor Interface: Homojunction or Heterojunction?

Surface engineering of photoelectrodes is considered critical for achieving efficient photoelectrochemical (PEC) cells, and various p-type materials have been investigated for use as photoelectrodes. Among these, the p-type semiconductor/n-type CdS heterojunction is the most successful photocathode structure because of its enhanced onset potential and photocurrent. However, it is determined that the main contributor to the enhanced activity is the Cd-doped layer and not the CdS layer. In this study, a Cd-doped n+p-buried homojunction of a CuInS2 photocathode is first demonstrated without a CdS layer. The homojunction exhibited a more active and stable PEC performance than the CdS/CuInS2 heterojunction. Moreover, it is confirmed that Cd doping is effective for other p-type materials. These results strongly suggest that the effects of Cd doping on photocathodes should be carefully investigated when designing CdS/p-semiconductor heterojunction photoelectrodes. They also indicate that the Cd-doped layer has great potential to replace the CdS layer in future photoelectrode designs.

Failure mechanism analysis and emerging strategies for enhancing the photoelectrochemical stability of photoanodes.

The development of efficient and stable photoanode materials is essential for driving the possible practical application of photoelectrochemical water splitting. This article begins with a basic understanding of the fundamentals of photoelectrochemical devices and photoanodes. State-of-the-art strategies for designing photoanodes with long-term stability are highlighted, including insertion of hole transport layers, construction of protective/passivation layers, loading of co-catalysts, construction of heterojunctions, and modification of the electrolyte. Based on the insights gained from these effective strategies, we present an outlook for addressing key aspects of the challenges of stabilizing photoanodes development in the future work. Widespread adoption of stability assessment criteria will facilitate reliable comparisons of results from different laboratories. In addition, deactivation of photoanode is defined as a 50% reduction in productivity. An in-depth understanding of the deactivation mechanism is essential for the design and development of efficient and stable photoanodes. This work will provide insights into the stability assessment of photoanode and facilitate the production of practical solar fuels.

Massive Onset Potential Shifting with an Epitaxial GaAs/Si Photocathode for Solar H2 Production

Solar photoelectrochemical (PEC) H2 production has the potential to solve one of the biggest issues confronting humanity nowadays: producing inexpensive, clean and renewable energy. Among various semiconductor materials, GaAs is an excellent candidate for the development of photoelectrodes within PEC cells for unassisted solar water splitting thanks to its appropriate band gap, good transport and optical properties and high quantum yield. However, the main limitations of GaAs photoelectrodes are related to the high substrate cost, their huge overpotentials and the short lifetime under operation. To address these issues, in this work, we report on the photocathode performance of 1 µm-thick GaAs layers grown on a low-cost Si p-doped substrate by MBE (Molecular Beam Epitaxy) and compare them to those of GaAs:p doped wafers . The photocathodes were investigated in 0.2 M H2SO4 (aq) electrolyte under 1 sun (100 mW/cm2) illumination. The onset potential (Vonset) of bare GaAs/Si and bare GaAs:p wafer is quite comparable, at around -0.2 V vs reversible hydrogen electrode (RHE). The significant reduction of surface states density with a sulfur passivation (S-passivation) by immersing samples in (NH4)2S solution is demonstrated but with very limited changes on the Vonset value, for both GaAs:p wafer and GaAs/Si photocathodes. In contrast, the deposition of thin Pt catalyst layers on both photocathodes by electroless deposition technique leads to a large positive shift Vonset. The Vonset of GaAs/Si and GaAs:p wafer photocathodes are increased up to 0.34 and 0.15 V vs RHE respectively. We show that the Vonset of GaAs/Si can be even improved by combining the Pt catalyst and the S-passivation process, reaching 0.4 V vs RHE (Fig. 1), a record value for GaAs-based Schottky-like photocathodes.STEM-EDX analysis was performed to investigate further the difference between Pt/GaAs/Si and Pt/GaAs:p wafer photocathodes. The EDX-line scans show that after the Pt electroless deposition, the Pt layer on GaAs:p wafer is homogeneous and shows an As0-rich Pt surface that can explain the weaker catalytic activity in comparison with GaAs/Si. Indeed, for the latter, Pt is deposited inhomogenously in the form of clusters leaving some bare surface. Here, As0 is expected to be more easily removed from the surface during the electroless deposition, resulting in more efficient catalyst properties of Pt. The morphology differences between the two Pt-coated electrodes are confirmed by XPS measurements. Since the process of electroless deposition strongly depends on the doping concentration of the materials deposited, the difference between GaAs:p wafer and GaAs/Si photocathodes is attributed to variations in their doping concentrations. Furthermore, the inhomogeneity of the Pt coating on GaAs/Si can also benefit to the passivation process by allowing the (NH4)2S solution to reduce more efficiently the surface defects at the oxide/semiconductor interface. Finally, the stability of Pt/GaAs/Si photocathodes was evaluated, and a lifetime larger than 112 h was established. These findings provide guidance for further studies towards the fabrication of scalable, cost-efficient and stable unassisted PEC cells for green hydrogen production. This research is supported by the “France 2030” French National Research Agency NAUTILUS Project (Grant no. ANR-22-PEHY-0013). Figure 1

Positive potential pretreatment of TiO2 photoanode towards efficient charge separation

Low charge separation efficiency (ηsep) of TiO2 impedes its applications of photoelectrochemical (PEC) water splitting. A positive potential pretreatment approach has been developed to construct a surface polarization with −OH groups at a potential of 1.48 VRHE. When the pretreatment time of 6 h is used, the ηsep and photocurrent density (Jph) reach up to 54 % (vs. 24 %, TiO2) and 0.92 mA cm−2 (vs. 0.32 mA cm−2, TiO2) under AM 1.5 G illumination, respectively. The photovoltage can be increased from 0.17 V to 0.52 V. When the pretreatment time is extended to 22 h, a higher Jph of 1.57 mA cm−2 and ηsep of 87 % can be obtained. Furthermore, the positive potential pretreated TiO2 possesses excellent PEC stability. The PEC improvements can be attributed to the surface polarization with the −OH groups and favorable surface states of Ti-OH, but not to the formation of Ti3+ or oxygen vacancies.

Photoelectrocatalytic Hydrogen Generation: Current Advances in Materials and Operando Characterization.

Photoelectrochemical (PEC) hydrogen generation is a promising technology for green hydrogen production yet faces difficulties in achieving stability and efficiency. The scientific community is pushing toward the development of new electrode materials and a better understanding of the underlying reactions and degradation mechanisms. Advances in photocatalytic materials are being pursued through the development of heterojunctions, tailored crystal nanostructures, doping, and modification of solid-solid and solid-electrolyte interfaces. Operando and in situ techniques are utilized to deconvolute the charge transfer mechanisms and degradation pathways. In this review, both materials development and Operando characterization are covered for advancing PEC technologies. The recent advances made in the PEC materials are first reviewed including the applied improvement strategies for transition metal oxides, nitrites, chalcogenides, Si, and group III-V semiconductor materials. The efficiency, stability, scalability, and electrical conductivity of the aforementioned materials along with the improvement strategies are compared. Next, the Operando characterization methods and cite selected studies applied for PEC electrodes are described. Operando studies are very successful in elucidating the reaction mechanisms, degradation pathways, and charge transfer phenomena in PEC electrodes. Finally, the standing challenges and the potential opportunities are discussed by providing recommendations for designing more efficient and electrochemically stable PEC electrodes.

Synthesis of CuO nanosheets on Cu foil via one-step wet chemical process at different reaction temperatures and their photoelectrochemical performance

Cupric oxide (CuO) nanostructures were directly grown on copper substrate via a simple one step solution-immersion process. The films were formed by the direct oxidation of copper in aqueous solution containing sodium hydroxide (NaOH) and ammonium persulfate (NH4)2S2O8. The influence of the reaction temperature on the structural, morphological, optical and photoelectrochemical (PEC) properties of the formed copper compounds nanostructures was investigated. The XRD and Raman spectroscopy results revealed the formation of Cu(OH)2/CuO composite for the samples prepared at 3 and 25 °C, and pure CuO was obtained for the samples prepared at 45 and 55 °C. The SEM micrographs showed that the formed Cu(OH)2 and CuO present a nanowire bundles and nanosheet morphology, respectively. The increase of the reaction temperature enhanced the absorbance of the CuO samples in the entire visible region. According to the photoelectrochemical measurements, the increase of the reaction temperature resulted in an improvement of the PEC response. The CuO nanosheets synthesized at 55 °C presents the highest and the most stable PEC response. A reasonable mechanism describing the formation of nanostructured copper compounds at different reaction temperatures is discussed in this paper.

Tailoring Phase Transition of Mo-S-Te Ternary System using Heat-Driven Process for Target Functionalities

Although structural engineering and phase modulation of transition metal dichalcogenides (TMDs) can be used to implement high-performance optoelectronic devices or energy cells, their expandability combined with individualized optimization for diverse applications using limited TMD materials is still challenging. Herein, we suggest an intriguing strategy to control the target functionalities of the Mo-S-Te ternary system using heat-driven crystallographic selection. The structure and phase alteration of the Mo-S-Te system can be effectively governed by modulating the thermal decomposition temperature, as evidenced by comprehensive spectroscopic and microscopic evaluations. The dual eligibility of the Mo-S-Te ternary system was validated by ascertaining the temperature-dependent selective enhancement of the optoelectronic properties or photoelectrochemical (PEC) performance as compared with those of bare MoS2. The Mo-S-Te synthesized at 300 °C exhibited superior photoresponse dynamics across various wavelengths, indicating its potential for advanced photodetection applications. In field of PEC, Mo-S-Te synthesized at 500 °C was highlighted as a promising photocathode material, offering enhanced PEC reactivity and stability. This study suggests the importance of material characteristics tailored to the synthetic conditions for target applications, which is a promising path to for the expansion of applicability in various areas using a simple approach that utilizes a limited range of TMD materials.

Porous GaP/g‐C3N4 Photoanode for Enhanced Hydrogen Production

AbstractThe g‐C3N4 decorated porous gallium phosphide have been fabricated by a facile electrophoretic deposition (EPD) process. The morphology, element composition and light absorption of the GaP/g‐C3N4 photoanode were observed using field‐emission scanning electron microscopy, X‐ray photoelectron spectroscopy, ultraviolet and visible spectrophotometer, respectively. When acting as photoanode, porous GaP/g‐C3N4 serves as a direct Z‐scheme system, where photogenerated holes in GaP are expended by electrons generated from the g‐C3N4, inhibiting the corrosion of GaP. Therefore, the porous GaP/g‐C3N4 showed a larger photocurrent density, which is 2.1 times as large as that of the porous GaP without g‐C3N4, and a more stable photocurrent density for over 10000 s (at 0 V vs RHE). Thus, this work delivers a practical way to improve the photoelectrochemical stability and property of III–V semiconductor materials, which could be used in solar energy conversion fields.

Photoelectrochemical degradation of selected organic pollutants on tungsten trioxide photoanodes

This study describes the photoelectrochemical degradation of model aromatic pollutants, viz. a herbicide (“monuron”, 3-(4-chlorophenyl)-1,1-dimethylurea) and an antimicrobial preservative (benzoic acid) on WO3 films prepared by aerosol pyrolysis. Crystalline WO3 films had a monoclinic structure, 4 μm thickness and a photocurrent density of 1 mA cm−2 at 1.2 V vs. RHE and illumination under 1 sun (simulated). The chemical and photoelectrochemical stability of WO3 films at various pH was evaluated. The dissolution rate at pH 1 and 4 was low (0.5 nm·h−1), whereas at pH 6 an increase in the dissolution rate to 15 nm·h−1 was observed. The course of the photoelectrochemical oxidation of selected pollutants was examined using HPLC. The achieved Faradaic efficiency of photoelectrooxidation of 1 mM benzoic acid divided by the number of charge equivalents per 1 mol of oxidised compound R, f/z, was 13 % and 12 % at pH 1 and 4, respectively, and for 1 mM monuron 7.2 % at pH 1 and 7.5 % at pH 4. Although the concentration of pollutants decreased significantly, UV–VIS and TOC (total organic carbon) analyses showed the prevalent presence of intermediates during the degradation. During the degradation of benzoic acid, hydroxybenzoic acid (salicylic acid) was found by HPLC as an early intermediary product.

Surface Engineering of BiVO4 Photoanodes for Photoelectrochemical Water Splitting: Recent Advances

AbstractEnergy demand worldwide demands clean, cheap, and renewable energy. Through the use of photoelectrochemical (PEC) conversion, solar energy can be transformed into chemical energy. Bismuth vanadate (BiVO4), a material exhibiting visible light activity, favourable conduction band edge energies, and ease of synthesis, has become increasingly popular in recent years. In BiVO4, charge carriers recombine rapidly, which adversely affects the PEC performance and stability. There have been several strategies developed to mitigate these deficiencies, including novel heterojunctions, doping with metals, coupling with cocatalysts, interface modification and modifying morphology. To achieve the best results, it is required to develop PEC devices with exceptional cost‐to‐efficiency ratios and long‐term durability. This review also examines novel yet commercially viable applications for BiVO4‐based photoanodes. Lastly, we discuss the challenges and perspectives facing PEC water splitting systems based on BiVO4.

Quantification of alloy atomic composition sites in 2D ternary MoS2(1-x)Se2x and their role in persistent photoconductivity, enhanced photoresponse and photo-electrocatalysis

Engineering transition metal dichalcogenides-based semiconducting two-dimensional (2D) layered materials for photo(electro)chemical (PEC) hydrogen evolution reaction (HER) by water splitting is an enduring challenge. Here, alloy-assisted photoconductivity and photoresponse from CVD-grown MoS2(1-x)Se2x (MSSE) 2D ternary atomic layered alloy-based photodetector device is presented for the realization of PEC HER. The explicit role of ‘S–Se’ and ‘Se2’ atomic alloy sites including chalcogen-induced vacancy defects on the photoconductivity/photoresponse and PEC HER performance of MSSE 2D alloy is investigated. Alloy formation, atomic site-by-site ‘Se’ composition and atomic structure are characterized using Raman/Photoluminescence (PL) spectroscopy, high-angle annular dark field (HAADF)- scanning transmission electron microscopy (STEM) extensively and supported with Auger Electron Spectroscopy (AES) mapping. Further, the local density and concentration of S–Se, Se2 atomic sites and defects were quantitatively estimated using HAADF-STEM image analysis in correlation with AES and it is found between the range of ∼15–20 % in MSSE alloy. A 10-fold high photoresponsivity in the case of MSSE concerning as-grown MS having fast photocurrent growth time and the prolonged decay time originates from the ‘Se’ and this alloy assisted states to enhance the PEC performance of MSSE alloy. The enhanced PEC HER activity of MSSE alloy was identified in terms of overpotential and current density. In addition, increased density of states as a function of ‘Se’ alloying, shifts in a p-band centre and lowers ΔGH* according to density functional theory calculations, which makes MSSE alloy an efficient HER activity. Further, the PEC stability and presence of the ‘S–Se’ and ‘Se2’ alloying and their role towards HER have been correlated by the spectral line shape analysis of PL and Raman spectra from post-PEC HER catalysts. These experimental and theoretical findings establish the role of chalcogen, and transition metal-based 2D alloy, leading to the design of new PECs of engineered 2D atomic layer interfaces.

Stacked High‐Entropy Hydroxides Promote Charge Transfer Kinetics for Photoelectrochemical Water Splitting

AbstractAlthough various kinds of cocatalyst are developed and decorated on the bismuth vanadate (BiVO4) photoanode, its photoelectrochemical (PEC) water splitting performance is limited owing to severe charge recombination and sluggish oxygen evolution reaction (OER). Herein, a high‐entropy hydroxide electrocatalyst (FeCoNiMoCrOOH) is constructed as a co‐catalyst deposited on BiVO4 with a good PEC activity and stability in potassium borate buffer, addressing substantial charge recombination and poor surface oxygen evolution reaction of the material. FeCoNiMoCrOOH synthesized by a simple electrodeposition stacking strategy, delivers an overpotential of 172 mV at 10 mA cm−2 with a stability of 600 h under alkaline conditions, representing one of the best performances on high‐entropy‐based catalysts. The FeCoNiMoCrOOH/BiVO4 photoanode shows a photocurrent density of 5.23 mA cm−2 at 1.23 VRHE with 100 h durability in potassium borate buffer. Experimental investigations and theoretical calculations demonstrate that the synergistic effect of Mo and Cr in FeCoNi catalyst effectively decreases the dissolution Fe, Co, and Ni after long‐term operation, increases the charge transfer kinetics, and promotes OER and PEC performances, therefore enhancing the photocorrosion resistance of BiVO4. This work provides a new avenue to design high entropy‐based electrocatalysts boosting solar water splitting activity and stability.

Facile synthesis of TiO2 nanothorn-coated Cu2O nanowires with improved stability and performance for photoelectrochemical water splitting

Copper(I) oxide (Cu2O) based photocathodes are promising in photoelectrochemical (PEC) water splitting due to their bandgap, natural abundance, and low cost. However, the stability issues have impeded their practical application. This study presents a solution through a novel photocathode, TiO2 nanothorns-coated Cu2O nanowires (TCNW), synthesized using simple wet chemical methods. TCNW outperformed pristine Cu2O nanowires (CNW), achieving a stable PEC current density of ∼3.8 mA∙cm−2 at 0 V vs RHE, compared to ∼1.9 mA∙cm−2 of CNW. TCNW also displayed an H2 evolution rate of ∼64.2 μmol∙cm−2∙h−1 with a 93.9% faradaic efficiency, whilst CNW reached only ∼6.8 μmol∙cm−2∙h−1 and 37.3%. These improvements stem from the protective TiO2 nanothorn layer, which enhances light absorption (300–500 nm) and improves charge separation and transfer by forming a p-n junction with Cu2O. This work underscores the importance of well-crafted surface p-n junctions and conformal protective layers in optimizing the efficiency and stability.

G-C3N4/TiO2 nanotube array for enhanced photoelectrochemical water splitting

Graphitic carbon nitride (g-C3N4) and TiO2 nanotubes (TNT) have made significant breakthroughs in the field of photocatalysis because of their unique features, such as environmental friendliness, low cost and good stability. Herein, we present the improved photo-electrochemical performance under AM 1.5G irradiation of three different photoanodes based on TNT coated with g-C3N4 via the effortless thermal treatment of anodized TNT sheets over melamine (TNT-M), urea (TNT-U) and dicyanamide (TNT -D). A maximum photocurrent of up to 0.14 mA cm−2 at 1.23 V (vs. RHE) is obtained under illumination using AM 1.5 G light source for TNT-D, which is ten times greater than pristine TNT (0.014 mA cm−2). A good photoelectrochemical stability with efficient charge transfer is observed, and electrochemical impedance spectra reveal that better photoelectrochemical performance is due to the reduced electron-hole pair recombination via the development of heterojunction between TNT and g-C3N4 compared to the bare-TNT electrode.

Solution Processing Silicon Heterojunction Photocathode for Efficient and Stable Hydrogen Production.

Efficient and stable photocathodes are crucial for the development of photoelectrochemical (PEC) water-splitting devices. Silicon heterojunction (SHJ) solar cell is one of the most advanced photovoltaic cells. However, due to the instability of its outermost indium tin oxide (ITO) layers in the electrolyte, a protective layer needs to be introduced on its surface. Previously reported high-quality protective layers almost all involved the use of expensive thin film manufacturing techniques such as atomic layer deposition (ALD). In this work, for the first time, a new strategy is proposed of modifying SHJ-based photocathode with yttrium hydroxide (Y(OH)3) through two-step solution methods to simultaneously improve the stability and activity. The optimized SHJ photocathode exhibits a high applied bias photon-to-current efficiency (ABPE) of 8.4% under simulated 100mWcm-2 (1 Sun) with an AM 1.5G filter in 0.5m KOH. Furthermore, the obtained SHJ photocathode demonstrates excellent stability of at least 110h at 0.3V versus RHE. In this work, combining facile direct current magnetron sputtering with a solution treatment technique provides a novel design strategy, which lowers the threshold for preparing high-quality protective layer, and paves the way for developing economic, efficient, and stable SHJ-based PEC devices.

The stability improvement of photoelectrochemical solar cells with Bi2S3 quantum dots sensitized photoanodes

Bi2S3, Bi2MoO6 and TiO2 composite photoanodes were fabricated using three different preparation routes to improve its photoelectrochemical (PEC) stability. The microstructure of three photoanodes are distinct significantly according to the results of XRD, SEM and TEM. The ordered TiO2 nanorod arrays (NRAs) and thinner Bi2MoO6 sheet crystals in flower-ball structure facilitate carrier transport and suppresses electron-hole recombination efficiently. The results of PEC tests indicate that the photoanode with Bi2MoO6 sheet crystals in flower-ball structure and TiO2 NRAs shows significant enhancement in PEC performance stability due to its ordered microstructure facilitating carrier transport and transfer and also good adherence of photoanode layer on FTO glass substrate. This photoanode in Bi2S3 quantum dots/Bi2MoO6@TiO2 NRAs structure exhibits satisfactory properties, achieving a PEC stability of 86.41% after 48 h.

Boosting photoelectrocatalytic oxygen evolution activity of BiVO4 photoanodes via caffeic acid bridged to NiFeOOH

Bismuth vanadate (BiVO4) is a promising n-type photoanode material for photoelectrochemical (PEC) water splitting. However, its activity is impeded by poor charge carrier transport and sluggish oxygen evolution kinetics. In this study, we reports a Fe doping and caffeic acid (CA)/NiFeOOH (NiFe) modification with BiVO4 photoanode (NiFe/CA/Fe-BiVO4) to enhance the PEC water oxidation performance and stability. The modified BiVO4 demonstrates significant advantages in promoting the PEC performance and stability. Specifically, Fe doping via in-situ electro-deposition results in smaller crystal sizes, larger specific surface areas, and more exposed active sites. Furthermore, co-catalyst NiFe connects with Fe-BiVO4 through CA bridge facilitates a more uniform self-assembly distribution of NiFe on BiVO4 surface. The NiFe/CA/Fe-BiVO4 exhibits an excellent photocurrent density of 6.2 mA/cm2 at 1.23 VRHEand demonstrates good stability at 0.8 VRHE. In addition, the composite photoanode shows a high applied bias photon-to-current efficiency (ABPE) value of 2.15% at 0.65 VRHE. EPR and in-situ FTIR confirm the generation of superoxide active species (O2- and ·O2-) during the PEC water oxidation reaction.

Photoilluminated Redox-Processed Rh2P Nanoparticles on Photocathodes for Stable Hydrogen Production in Acidic Environments.

While photoelectrochemical (PEC) cells show promise for solar-driven green hydrogen production, exploration of various light-absorbing multilayer coatings has yet to significantly enhance their hydrogen generation efficiency. Acidic conditions can enhance the hydrogen evolution reaction (HER) kinetics and reduce overpotential losses. However, prolonged acidic exposure deactivates noble metal electrocatalysts, hindering their long-term stability. Progress requires addressing catalyst degradation to enable stable, efficient, and acidic PEC cells. Here, we proposed a process design based on the photoilluminated redox deposition (PRoD) approach. We use this to grow crystalline Rh2P nanoparticles (NPs) with a size of 5-10 on 30 nm-thick TiO2, without annealing. Atomically precise reaction control was performed by using several cyclic voltammetry cycles coincident with light irradiation to create a system with optimal catalytic activity. The optimized photocathode, composed of Rh2P/TiO2/Al-ZnO/Cu2O/Sb-Cu2O/ITO, achieved an excellent photocurrent density of 8.2 mA cm-2 at 0 VRHE and a durable water-splitting reaction in a strong acidic solution. Specifically, the Rh2P-loaded photocathode exhibited a 5.3-fold enhancement in mass activity compared to that utilizing just a Rh catalyst. Furthermore, in situ scanning transmission electron microscopy (STEM) was performed to observe the real-time growth process of Rh2P NPs in a liquid cell.