International Journal of Hydrogen Energy Formatting Requirements: Complete Author Guide

IJHE uses a standard Elsevier abstract format.

• Word limit: 200 words for Research Articles, 250 for Reviews
• Structure: Single unstructured paragraph
• Citations: Not allowed
• Abbreviations: Define at first use in the abstract
• Keywords: 4 to 6 keywords required below the abstract

The abstract should cover what you studied, how you approached it, what you found, and why it matters. For hydrogen energy research specifically, reviewers expect the abstract to include quantitative performance metrics. Saying "the catalyst showed improved performance" without a number is insufficient. State the specific hydrogen production rate, faradaic efficiency, power density, or whatever your primary performance metric is.

Keywords at IJHE drive the editor assignment process. The journal covers everything from photocatalytic water splitting to solid-state hydrogen storage to PEM fuel cells. If your keywords are too broad (e.g., "hydrogen," "energy"), your manuscript might land with an editor whose expertise doesn't match your topic. Be specific: "proton exchange membrane," "metal-organic framework hydrogen storage," or "alkaline water electrolysis."

IJHE follows Elsevier's standard figure guidelines with some discipline-specific expectations.

Figure specifications:

Discipline-specific figure expectations:

Electrochemical plots (cyclic voltammograms, polarization curves, impedance spectra) need to follow standard electrochemistry conventions. Potential axes should use the correct reference electrode label. Current density should be reported per geometric area unless specified otherwise. Nyquist plots should have equal axis scaling.

For electron microscopy images (SEM, TEM, HR-TEM), scale bars are mandatory. Include the accelerating voltage and magnification in the caption. Energy-dispersive X-ray spectroscopy (EDS) mapping should use color-coded element overlays with a clear legend.

Performance comparison charts are extremely common in IJHE papers. If you're showing a bar chart or table comparing your catalyst/material to literature benchmarks, include the test conditions (temperature, pressure, electrolyte concentration) for each data point. Reviewers routinely flag unfair comparisons where test conditions aren't matched.

Highlights are mandatory for all IJHE article types and are a common source of desk rejections.

• Count: 3 to 5 bullet points
• Character limit: 85 characters per highlight, including spaces
• Submission: Uploaded as a separate file
• Content: Specific, quantitative findings

The 85-character limit forces extreme conciseness. For hydrogen energy papers, this means stating the result with a number.

Bad highlight (96 characters): "We developed a novel photocatalyst for hydrogen production with excellent performance and stability"

Good highlight (83 characters): "NiMoS/CdS photocatalyst achieved 42.7 mmol/g/h H2 evolution under visible light"

Highlights are indexed by search engines and displayed on the ScienceDirect article page. They're functionally the most visible text in your paper after the title and abstract.

IJHE uses the standard Elsevier numbered reference style.

In-text citations: Numbers in square brackets [1], [2,3], [4-7]. Numbered in order of first appearance.

Reference list format:

[1] A.B. Author, C.D. Author, Title of article, Int J Hydrogen Energy Volume (Year) Pages.

Key formatting details:

• Author names: Initials first, then surname
• Commas between authors
• Journal names abbreviated per ISO 4
• Volume in bold
• DOIs strongly recommended
• Web references need access dates

There's no stated reference cap, but Research Articles typically cite 40 to 70 papers. IJHE is a field where the literature is growing rapidly, and reviewers expect thorough citation of recent work. Underciting recent publications (especially in active subfields like green hydrogen or solid oxide cells) signals to reviewers that your literature review is incomplete.

One formatting detail specific to IJHE: when citing standards documents (ISO, ASTM, DOE technical reports), include the full standard number and year. These references are common in fuel cell and hydrogen storage papers and are frequently formatted inconsistently.

IJHE supports supplementary material hosted on ScienceDirect.

Accepted content:

• Extended experimental procedures
• Additional characterization data (XRD, XPS, BET, TGA)
• Supporting electrochemical data
• Video content (operando experiments, durability testing)
• Computational details and input files

Formatting requirements:

• Single PDF file preferred for text and figures
• Excel files for large datasets
• Label as Fig. S1, Table S1, etc.
• Each item cited in the main text
• Maximum 50 MB per file

For computational papers (DFT studies of catalysts, molecular dynamics of hydrogen diffusion), IJHE expects calculation parameters, convergence criteria, and optimized atomic coordinates in the supplementary material. Reviewers in computational hydrogen energy are particularly thorough about checking methodology details.

Data deposition is increasingly expected. For large datasets (performance databases, screening results), deposit in Mendeley Data or a domain-specific repository and include the DOI in a data availability statement.

Details specific to IJHE that aren't obvious from the general author guidelines:

Nomenclature section. IJHE encourages (and many editors expect) a Nomenclature section at the beginning of the paper, after the abstract and before the Introduction. This lists all symbols, Greek letters, subscripts, and abbreviations used in the paper. It's not formally required, but hydrogen energy papers tend to be symbol-heavy, and the Nomenclature section is standard practice in the field.

Units must follow SI conventions. This is strictly enforced. Use L/min (not lpm), kPa (not psi), and Celsius (not Fahrenheit). The one exception: pressures in hydrogen storage papers are sometimes reported in bar alongside MPa, since bar is the industry convention for high-pressure hydrogen systems.

CRediT author statement is mandatory. Like all Elsevier journals, IJHE requires a CRediT author contribution statement. The submission system won't let you complete the process without it.

Declaration of competing interests. Mandatory for all manuscripts. Even if there are no conflicts, you must include a statement saying so. The journal has a specific template: "The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper."

IJHE is particularly strict about novelty claims. The journal's rejection rate is high (around 80%), and a common rejection reason is insufficient novelty. Formatting-wise, this means your Introduction must clearly state what's new about your work compared to existing literature. A dedicated "Novelty of this work" paragraph at the end of the Introduction is common and appreciated by editors.

Hydrogen safety statements. For experimental papers involving high-pressure hydrogen, the journal doesn't require formal safety statements in the paper, but reviewers occasionally ask about safety protocols. Having a brief mention of safety measures in the experimental section can preempt these questions.

The most common issues that delay IJHE manuscripts:

1. Highlights exceeding 85 characters. The submission system enforces this strictly. Authors frequently need to rewrite their highlights at the submission stage, leading to rushed, vague statements.

1. Tables counted in word limit. Many authors calculate their word count without tables and then get flagged during technical review. Count everything except the abstract, references, and supplementary material.

1. Missing Nomenclature section. While not formally required, omitting it for a symbol-heavy paper almost guarantees a reviewer comment asking for one.

1. Inconsistent units. Mixing unit systems (bar and MPa, mL and cm3) within the same paper is flagged by reviewers and sometimes by the editorial office.

1. Missing CRediT statement. The submission system blocks you, but authors sometimes fill it in generically, which leads to reviewer pushback.