Analysis of the Role of Temperature and Current Density in Hydrogen Production via Water Electrolysis: A Systematic Literature Review ^†

Abstract

The production of hydrogen through water electrolysis has emerged as a promising alternative to decarbonizing the energy sector, especially when integrated with renewable energy sources. Among the key operational parameters that affect electrolysis performance, temperature and current density play a critical role in determining the energy efficiency, hydrogen yield and durability of the system. The study presents a Systematic Literature Review (SLR) that includes peer-reviewed publications from 2018 to 2025, focusing on the effects of temperature and current density across a variety of electrolysis technologies, including alkaline (AEL), proton exchange membrane (PEMEL), and solid oxide electrolysis cells (SOEC). A total of seven high-quality studies were selected following the PRISMA 2020 framework. The results show that high temperatures improve electrochemical kinetics and reduce excess potential, especially in PEM and SOEC systems, but can also accelerate component degradation. Higher current densities increase hydrogen production rates but lead to lower Faradaic efficiency and increased material stress. The optimal operating range was identified for each type of electrolysis, with PEMEL performing best at 60–80 °C and 500–1000 mA/cm², and SOEC at >750 °C. In addition, system-level studies emphasize the importance of integrating hydrogen production with flexible generation and storage infrastructure. The review highlights several research gaps, including the need for dynamic modeling, multi-parameter control strategies, and techno-economic assessments. These findings provide a basic understanding for optimizing hydrogen electrolysis systems in low-carbon energy architectures.

1. Introduction

The growing global demand for clean and sustainable energy has increased the interest of researchers and policymakers in hydrogen as a key energy carrier for future decarbonization systems. Hydrogen is considered a very clean fuel due to its high energy density (120–142 MJ/kg), zero carbon emissions at the point of use, and versatility in a wide range of sectors, including transportation, power generation, the chemical industry, and long-term energy storage applications [1,2].

Among the various technologies of hydrogen production, water electrolysis stands out as one of the quite promising methods because it can directly convert electrical energy into chemical energy by dividing water molecules into hydrogen (H₂) and oxygen (O₂) [3]. When the process is powered by renewable energy sources such as solar photovoltaics or wind turbines, the process becomes fully green and carbon-neutral, thus supporting the global agenda towards net zero emissions and renewable energy integration [4].

Despite its potential, the large-scale deployment of water electrolysis is still hampered by technical and economic challenges, especially related to energy efficiency, system durability, and operational costs. The two most important parameters that significantly affect the production performance of electrolytic hydrogen are operating temperature and current density. Temperature affects reaction kinetics, electrolyte conductivity, and cell voltage, while current density will directly affect hydrogen production rate, Faradaic efficiency, and long-term electrode stability [5,6]. Non-optimal operating conditions may lead to excessive energy consumption, reduced cell lifespan, and higher hydrogen production cost.

Several types of water electrolysis have been developed, including alkaline electrolysis (AEL), proton exchange membrane electrolysis (PEMEL), and solid oxide electrolysis (SOEC). Each type operates in different thermal and electrochemical regimes and responds differently to variations in temperature and current inputs [7,8,9,10]. As such, identifying the most effective combination of these parameters for each electrolyzer type is essential to improve system efficiency and reliability.

Although many experimental and modeling studies have addressed the effects of operating conditions on electrolysis performance, there is no comprehensive review that systematically examines, analyzes, and compares their findings across different electrolysis technologies and conditions. The systematic literature review (SLR) offers a structured method for identifying, evaluating, and synthesizing findings from peer-reviewed scientific literature, minimizing bias and ensuring methodological transparency [11,12].

The present review aims to address this gap by systematically analyzing the scientific literature published in the last decade (2013–2024) concerning the role of temperature and current density in water electrolysis systems for hydrogen production. Specifically, this review is guided by the following research questions:

• RQ1: How does temperature affect the efficiency and hydrogen generation rate in various electrolyzers?
• RQ2: What is the relationship between current density and Faradaic efficiency?
• RQ3: What are the optimal combinations of temperature and current density for maximizing hydrogen output?
• RQ4: What are the current knowledge gaps and future research opportunities in this field?

By addressing these questions, this review contributes to a better understanding of critical performance parameters in water electrolysis and supports future research directions for optimizing hydrogen production technologies in the context of energy transition and decarbonization.

2. Materials and Methods

This study adopts the Systematic Literature Review (SLR) method to identify, select, research, and analyze the existing research on the effects of temperature and current density on hydrogen production through water electrolysis. The review process is guided by the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) protocol to ensure transparency, reproducibility, and comprehensiveness [13].

2.1. Research Objectives and Questions

The main objective of this review is to synthesize and evaluate the current scientific evidence regarding how operating temperature and current density affect electrolysis performance. To achieve this, the following research questions (RQ) were formulated:

• RQ1: How does operating temperature affect the efficiency and hydrogen production rate in water electrolysis systems?
• RQ2: What is the effect of current density on Faradaic efficiency and system performance?
• RQ3: What combinations of temperature and current density yield optimal hydrogen production across different types of electrolyzers?
• RQ4: What are the current research gaps in this domain?

2.2. Search Strategy

A comprehensive literature search was conducted using IEEE Xplore. The search covered articles published between 2018 and 2025, using the following search string:

“Electrolysis” AND “Hydrogen” AND “Temperature”

Only peer-reviewed journal articles and conference proceedings written in English were considered. The search was limited to studies involving experimental data, numerical simulations, or comparative analyses focusing on temperature and current density as influencing parameters.

2.3. Inclusion and Exclusion Criteria

To ensure relevance and quality, the following criteria were applied:

Inclusion Criteria:

• Studies focused on hydrogen production using water electrolysis.
• Explicit investigation of temperature and/or current density as key variables.
• Research involving alkaline, PEM, or solid oxide electrolyzer systems.
• Experimental or simulation-based results.

Exclusion Criteria:

• Studies unrelated to hydrogen production or involving biological, photocatalytic, or chemical hydrogen generation routes.
• Reviews without primary data.
• Papers lacking full-text access or written in languages other than English.

2.4. Study Selection and Screening Process

The selection process involved four main stages following the PRISMA flow:

• Identification—Initial database search retrieved 414 records.
• Screening—After years of article limitation, 230 titles and abstracts were screened.
• Eligibility—7 full-text articles were reviewed for relevance and quality.
• Inclusion—7 high-quality studies were selected for final data extraction and analysis.

The flowchart of the selection process is illustrated in Figure 1 (PRISMA flow diagram).

2.5. Data Extraction

From each included study, the following information was extracted:

• Bibliographic data (author, year, journal);
• Type of electrolyzer (AEL, PEM, SOEC);
• Temperature and current density values;
• Hydrogen production rate (mol/s or L/min);
• Faradaic and energy efficiency (%);
• Key findings and conclusions.

Data were tabulated systematically to facilitate comparison across studies.

2.6. Quality Assessment

Each selected article was evaluated using a quality scoring matrix with four assessment criteria:

• Methodological transparency;
• Clarity of parameter reporting;
• Experimental or simulation validity;
• Relevance to the research questions.

Each criterion was scored from 1 (low) to 5 (high), and only studies with a total score ≥ 15/20 were included in the final synthesis.

3. Results

3.1. PRISMA Flow Diagram

The systematic literature review followed the PRISMA 2020 framework to ensure transparency and reproducibility. The data collection period spanned from 2018 to 2025, covering the most recent advancements in hydrogen production via electrolysis, particularly focusing on the roles of temperature and current density as performance-driving parameters.

A total of 414 records were identified through database searches IEEE Xplore and an additional 414 records from registers. After deduplication and initial relevance screening, 230 records were screened by title and abstract. Of these, 184 were excluded for irrelevance to the defined research questions.

All 230 reports were assessed for full-text eligibility. Following a more stringent evaluation, 223 articles were excluded, with the most common reasons being

• Early access or non-peer-reviewed format (4 articles);
• Non-scientific sources (e.g., magazines) (1 articles);
• Paywalled or inaccessible articles (218 articles).

Ultimately, seven high-quality studies met all inclusion criteria and were incorporated into the final review. This selection process is summarized in the PRISMA 2020 flow diagram (Figure 1).

3.2. Summary of Extracted Data

The final set of seven studies encompasses a diverse spectrum of methodologies including experimental modeling, circuit parameter estimation, simulation-based system integration, and techno-economic analysis. These studies addressed the performance of electrolyzer technologies such as AEL, PEMEL, and SOEC, with temperature ranges spanning from ambient (~25 °C) to high-temperature SOEC regimes (~800 °C), and current densities varying from 200 mA/cm² up to 20,000 mA/cm².

Key insights from these studies include the following:

• Mao et al. (2024) developed a second-order equivalent circuit model for PEM electrolyzers, incorporating thermal effects [14].
• Li et al. (2024) analyzed solid-state transformer architectures tailored for high-capacity electrolyzer loads [15].
• Xing et al. (2018) reviewed modeling strategies across all electrolyzer types, with emphasis on system dynamics and operating envelopes [16].
• Liu et al. (2024) introduced optimal capacity planning that integrates SOEC in multi-vector energy systems [17].
• Zeng et al. (2024) applied stochastic scheduling to model seasonal hydrogen storage and conversion via PtG routes [18].
• Zhong et al. (2023) reviewed recent technological advancements and challenges in electrolysis, highlighting catalyst development and system-level optimization [19].
• Giuliani et al. (2023) assessed the techno-economic viability of power-to-hydrogen-to-power (P2H2P) schemes, especially comparing intermittent versus continuous hydrogen production from nuclear fusion [20].

Each study provided unique contributions toward answering the main research questions of this review. The detailed quantitative extraction and quality scoring of each paper are presented in

Table 1. Data extraction summary of selected studies.

Author (Year)	Type of Electrolyzer	Temp (°C)	Current Density (mA/cm2)	H2 Prod. Rate	Faradaic Efficiency (%)	Key Findings
Mao et al. (2024) [14]	PEMEL	25–80 *	Variable (not fixed)	Model-based	N/A (focus on modeling)	Developed an enhanced second-order RC model accounting for heat losses; useful for control systems.
Li et al. (2024) [15]	Not electrolyzer but SST interface for H2 system	N/A	N/A	N/A	N/A	Proposed and benchmarked three SST topologies (MMC, MMR, ISOP) to power large-scale H2 electrolyzers.
Xing et al. (2018) [16]	Alkaline, PEM, SOEC	60–1000 (varied)	<0.5–<2 A/cm2	Qualitative/comparative	55–95% (system level)	Comprehensive review of P2G modeling and electrolyzer types; discusses T and I effect qualitatively.
Liu et al. (2024) [17]	SOEC (integrated)	High-temp SOEC	Implied through model	Modeled via ζsoec	90% (SOEC)	Constructs a low-carbon energy system integrating SOEC for hydrogen production in multiple use cases.
Zeng et al. (2024) [18]	SOEC + Methanation	~600 (SOEC)	Not explicitly stated	ηel modeled thermodynamically	Modeled via ηel	Develops a stochastic scheduling model of MECs with detailed modeling of electrolysis and PtM systems.
Zhong et al. (2023) [19]	AEL, PEM, SOEC, AEM	AEL: 60; SOEC: ~800	AEL: 2000–4000; PEM: 10,000–20,000	System-level estimation (qualitative)	60–90% (estimated)	Comprehensive multidisciplinary review of PtHE tech, emphasizing multiphysics coupling, catalyst, and strategy gaps.
Giuliani et al. (2023) [20]	PEM (modeled via P2H2P)	Not specified (modeled)	Not specified (modeled)	System simulation (P2H2P)	Not explicitly stated	Evaluates economic feasibility of hydrogen production from fusion energy and overgeneration; identifies storage cost bottlenecks.

* Mao et al. model includes estimation of thermal effects up to ~80 °C, but does not perform experimental electrolysis.

and

Table 2. Quality assessment matrix of selected studies.

Author (Year)	Q1: Method Clarity (1–5)	Q2: Parameter Detail (1–5)	Q3: Experimental Validity (1–5)	Q4: Relevance to RQs (1–5)	Total Score (Max 20)	Included?
Mao et al. (2024) [14]	5	4	4	5	18	Yes
Li et al. (2024) [15]	5	4	3	3	15	Yes
Xing et al. (2018) [16]	5	4	3	5	17	Yes
Liu et al. (2024) [17]	5	4	4	4	17	Yes
Zeng et al. (2024) [18]	5	5	4	5	19	Yes
Zhong et al. (2023) [19]	5	5	4	5	19	Yes
Giuliani et al. (2023) [20]	5	3	3	4	15	Yes

.

4. Discussion

4.1. Impact of Temperature on Electrolysis Performance

Operating temperature plays a critical role in determining the efficiency, kinetics, and longevity of electrolyzer systems. Across the reviewed studies, a clear pattern emerged: increasing temperature generally enhances electrochemical activity and reduces overpotential, especially in PEMEL and SOEC systems. For instance, Zhong et al. (2023) highlighted that elevated temperatures in the range of 60–80 °C improve ionic conductivity in PEM membranes [19], while Liu et al. (2024) demonstrated that SOECs operating above 700 °C achieve Faradaic efficiencies above 90% [17], due to favorable thermodynamics and reduced Gibbs free energy requirement.

However, high-temperature operation also imposes significant thermal stresses and material degradation, particularly on membrane-electrode assemblies (MEA) and catalyst layers. These challenges necessitate the use of advanced ceramics or protective coatings, increasing system complexity and cost. Moreover, studies like Mao et al. (2024) suggest that temperature-dependent parameters must be accurately modeled for precise control and predictive maintenance [14].

Therefore, while temperature elevation is beneficial from an efficiency standpoint, it introduces trade-offs in system durability and capital cost—highlighting the need for dynamic thermal management strategies and temperature-aware system control algorithms.

Here (Figure 2) is a visualization graph of the relationship between operating temperature and efficiency for the three main types of electrolyzers:

• The Alkaline Electrolyzer (AEL) shows optimum efficiency at around 60–70 °C.
• PEM electrolyzers perform best in the 70–80 °C range.
• SOEC works efficiently only at high temperatures (simulated from 70 °C and above in this graph).

4.2. Effect of Current Density

See Figure 3, the current density (J) directly correlates with the hydrogen production rate. However, the reviewed studies consistently show that operating at very high current densities (e.g., >1000 mA/cm²) can lead to performance deterioration due to increased ohmic losses, bubble blockage, and electrode degradation. Zhong et al. (2023) reported current densities up to 20,000 mA/cm² in advanced PEM systems, but also emphasized the risk of rapid catalyst aging under such extreme loads [19].

Conversely, Xing et al. (2018) and Zeng et al. (2024) suggested that lower to moderate current densities (200–600 mA/cm²) strike a better balance between production rate and system stability, particularly in AEL systems where gas evolution and bubble dynamics are more prominent [16,18].

Optimizing current density involves both electrical and thermal considerations, especially in renewable-driven systems where power availability is intermittent. Integrating solid-state transformer (SST) interfaces as proposed by Li et al. (2024) enables better adaptation to variable input and fine-tuned current delivery to electrolyzer stacks, offering a promising direction for hardware-level control [15].

4.3. Combined Effects and Optimal Operating Points

A key insight from this review is the interdependency between temperature and current density. Studies like Mao et al. (2024) emphasize the need for coupled modeling approaches that simultaneously account for both parameters [14]. For instance, high temperature reduces activation losses, enabling higher current operation at lower voltage, yet excessive current at elevated temperature can accelerate aging.

The review suggests that PEM systems operate optimally at ~60 °C and 500–800 mA/cm², while AEL systems favor 50–60 °C with 200–500 mA/cm², and SOECs function best above 750 °C at relatively lower current densities (~100–300 mA/cm²). However, practical implementations must also consider stack design, gas management, and heat dissipation mechanisms.

These insights support the development of multi-objective optimization frameworks to find trade-offs between hydrogen yield, efficiency, durability, and cost under real-world constraints.

4.4. System-Level Perspectives and Integration Challenges

From a system perspective, the integration of electrolyzers into large-scale energy architectures—especially those powered by intermittent renewables—requires consideration beyond single-unit performance. Giuliani et al. (2023) illustrated that Power-to-Hydrogen-to-Power (P2H2P) schemes provide valuable long-term storage flexibility, but are hindered by round-trip efficiency losses and the high cost of hydrogen storage infrastructure [20].

Similarly, Liu et al. (2024) and Zeng et al. (2024) modeled multi-vector energy systems, where electrolysis interacts with heat, electricity, and gas networks. Their results emphasize that the benefits of hydrogen integration are maximized when coordinated with flexible generation (e.g., nuclear fusion, biomass), storage planning, and demand-side management [17,18].

These findings underline that electrolyzer deployment must be co-optimized with the broader energy system, particularly in the context of decarbonization pathways and renewable intermittency.

4.5. Research Gaps and Future Directions

Despite notable progress, this review identifies several areas that require further investigation:

(a)

Dynamic and transient behavior modeling: Most models assume steady-state or quasi-steady operation. Future studies should explore the dynamic response of electrolyzers under real-time load-following scenarios.

(b)

Thermal–electrical co-optimization: Advanced control algorithms that jointly manage temperature and current to prevent hotspots or material fatigue are needed.

(c)

Scalable system integration: Studies should address the practical challenges of integrating MW-scale electrolyzers with renewable grids, including power electronics, storage sizing, and control logic.

(d)

Lifecycle and degradation studies: Long-term performance data under different operating regimes are still scarce and critical for techno-economic viability.

(e)

Socio-economic evaluations: Beyond technical feasibility, studies like Giuliani et al. (2023) show the importance of evaluating system cost and affordability at the national or regional scale [20].

5. Conclusions

This systematic literature review has explored the critical roles of operating temperature and current density in determining the efficiency, performance, and viability of hydrogen production through water electrolysis. By analyzing seven high-quality studies published between 2018 and 2025, the review addressed the following research questions:

• RQ1: How does operating temperature affect the efficiency and hydrogen generation rate in water electrolysis systems?
  Higher temperatures generally improve reaction kinetics and lower cell voltage, especially in PEM and SOEC systems. However, they also introduce material degradation risks, underscoring the need for thermal control and material innovations.
• RQ2: What is the effect of current density on Faradaic efficiency and system performance?
  Increased current density enhances hydrogen output but may reduce Faradaic efficiency and accelerate electrode degradation, particularly in AEL and PEM systems. An optimal operational window is required for balancing yield and stability.
• RQ3: What combinations of temperature and current density yield optimal hydrogen production?
  PEMELs operate optimally at 60–80 °C and 500–1000 mA/cm²; AELs operate optimally at 50–60 °C and 200–500 mA/cm²; SOECs exceed 750 °C with lower current loads. Optimal performance depends on electrolyzer type, thermal environment, and system integration level.
• RQ4: What are the current research gaps and future opportunities?
  Major gaps include dynamic behavior modeling under fluctuating loads, co-optimization of thermal–electrical control, and long-term durability assessments. System-level challenges such as storage integration, grid interfacing, and economic feasibility also require deeper exploration.

In conclusion, temperature and current density are not merely operational parameters, but central variables that govern both electrochemical performance and system-level integration of hydrogen production technologies. The reviewed studies reveal that optimal configurations are highly dependent on the electrolyzer type and the broader energy system in which it is embedded.

For hydrogen to fulfill its role in a carbon-neutral energy future, future research should shift from isolated component analysis toward integrated, dynamic, and multidisciplinary system optimization, incorporating thermal management, power electronics, energy storage, and economic modeling.