Available online at website: https://journal.
id/index.
php/bcrec Bulletin of Chemical Reaction Engineering & Catalysis, 21 .
2026, x-x Original Research Article Effect of Sodium Borohydride to Ferric Chloride Molar Ratios on Nanoscale Zero-Valent Iron for Hydrogen Generation from Formic Acid Siti Aishah Yusuf1.
Meor Saiful Rizal Meor Ahmad Zubairi2.
Siti Fatimah Abdul Halim1.
Siu Hua Chang1* 1Waste Management and Resources Recovery (WeResCu.
Group.
Faculty of Chemical Engineering.
Universiti Teknologi MARA.
Cawangan Pulau Pinang, 13500 Permatang Pauh.
Pulau Pinang.
Malaysia.
2Graphite Signature Sdn Bhd, 31650 Ipoh.
Malaysia.
Received: 13th January 2026.
Revised: 4th March 2026.
Accepted: 5th March 2026 Available online: 10th March 2026.
Published regularly: August 2026 Abstract Hydrogen generation from formic acid using nanoscale zero-valent iron .
ZVI) represents a promising route for lowcost and sustainable hydrogen production.
However, the effect of sodium borohydride (NaBHCE) to ferric chloride (FeClCE) molar ratio on nZVI synthesis and performance remains insufficiently explored.
This study investigated how varying NaBHCE:FeClCE molar ratios affect nZVI synthesis characteristics and its hydrogen generation efficiency from formic acid, which acts as a safe and easily handled hydrogen carrier.
nZVI was synthesized through a one-step liquid-phase chemical reduction method using NaBHCE:FeClCE ratios ranging from 4.
4:1 to 8.
8:1.
UVAeVis spectroscopy indicated that 4:1 ratio yielded the highest nZVI formation, reflecting optimal reduction efficiency and particle formation.
Hydrogen generation experiments conducted in a closed reactor equipped with a water displacement system revealed that nZVI synthesized at the 4.
4:1 ratio achieved the maximum hydrogen volume .
mL), which progressively declined to 53 mL at the 8.
8:1 ratio.
These findings demonstrate that precursor molar ratios significantly influence nZVI formation, stability, and reactivity toward hydrogen evolution.
An optimal NaBHCE:FeClCE ratio of 4.
4:1 was identified for maximizing nZVI formation and hydrogen volume, providing valuable insights for developing scalable formic acidAe based hydrogen generation systems.
Copyright A 2026 by Authors.
Published by BCREC Publishing Group.
This is an open access article under the CC BY-SA License .
ttps://creativecommons.
org/licenses/by-sa/4.
Keywords: Hydrogen.
Nanoscale Zero-Valent Iron.
Formic acid.
Sodium borohydride.
Molar Ratio How to Cite: Yusuf.
Meor Ahmad Zubairi.
Abdul Halim.
Chang.
Effect of Sodium Borohydride to Ferric Chloride Molar Ratios on Nanoscale Zero-Valent Iron for Hydrogen Generation from Formic Acid.
Bulletin of Chemical Reaction Engineering & Catalysis, 21 .
, x-x.
(DOI: 10.
9767/bcrec.
Permalink/DOI: https://doi.
org/10.
9767/bcrec.
Introduction Hydrogen is a vital industrial commodity extensively used in ammonia synthesis, petroleum refining, methanol production, and the steel industry .
Global hydrogen demand exceeded 94 million tonnes in 2021 and continues to rise, driven by the growth of the industrial and energy sectors .
Currently, more than 99% of hydrogen is produced from fossil-based processes such as steam methane reforming, partial * Corresponding Author.
Email: shchang@uitm.
my (S.
Chan.
oxidation of hydrocarbons, and coal gasification .
These methods are energy-intensive and generate substantial greenhouse gas emissions.
Although water electrolysis offers a cleaner option using renewable electricity, its widespread adoption remains constrained by high energy costs and dependency on intermittent renewable sources .
Therefore, developing simpler and more sustainable hydrogen production routes is urgently required, mirroring similar efforts being implemented across other industrial processes .
Ae bcrec_20634_2026 Copyright A 2026.
ISSN 1978-2993.
CODEN: BCRECO
Bulletin of Chemical Reaction Engineering & Catalysis, 21 .
, 2026, 483 Among emerging approaches, formic acid (HCOOH) has attracted attention as a liquid hydrogen carrier due to its high hydrogen content .
4 wt%), safety, and stability under ambient conditions .
Conventional formic acid decomposition typically relies on noble metal catalysts such as palladium, platinum, and ruthenium .
However, these catalysts are expensive and may produce carbon-containing byproducts such as CO and COCC, particularly when low-cost base metals are used .
Recently.
Singh et al.
demonstrated that nZVI can generate hydrogen from formic acid through a direct redox process without forming carboncontaining gaseous byproducts, as expressed in Equation .
Fe0 .
2yayayayayayayayayaya(E.
2yaya2 ycCycC Ie yayayaya.
2yaya2 ycCycC.
FeA Ie FeAA 2eA In this system, hydrogen evolution proceeds through a direct redox mechanism rather than a catalytic pathway.
FeA acts as a sacrificial reductant and electron donor.
Upon contact with formic acid, surface FeA atoms are oxidized to FeAA .
The released electrons are transferred to protons generated from the dissociation of formic acid in aqueous solution:
HCOOHNUHA HCOOA
2HA 2eA Ie HCC.
The overall simplified reaction can therefore be written as:
FeA 2HCOOH Ie FeAA 2HCOOA HCC.
The electron transfer and hydrogen generation process is illustrated in Figure 1.
The electron transfer occurs directly at the nZVI surface, where adsorbed protons are reduced to molecular hydrogen.
The nanoscale dimension of nZVI enhances this process by providing a high surface area, short electron diffusion pathways, and abundant active FeA sites.
Importantly.
FeA is consumed during the reaction, confirming its role as a stoichiometric reductant rather than a The generated FeAA subsequently coordinates with formate ions to form stable iron(II) formate dihydrate.
Fe(HCOO)CCA2HCCO.
This mechanism explains the high hydrogen purity and the absence of carbon-containing gaseous byproducts.
The nZVI can be synthesized through various methods, including ball milling, carbothermal ultrasound-assisted biological routes, and chemical reduction .
Ae.
Among these, chemical reduction using sodium borohydride (NaBHCE) is the most widely adopted due to its simplicity and ability to produce highpurity nanoparticles.
The synthesis typically follows the reaction shown in Equation .
2yayayayayayayaya3 6ycAycAycAycAycAycAycAycA4 18yaya2 ycCycC Ie 2yayayaya 0 6ycAycAycAycAycAycAycAycA 6yaAyaA.
cCycCycCycC)3 21yaya2 In this method, the NaBHCE:FeClCE molar ratio plays a critical role in determining reduction efficiency and particle characteristics.
Although a theoretical ratio of 3:1 is required for complete reduction of FeAA to FeA, excess NaBHCE is often used to compensate for hydrolysis and side reactions .
,21,.
However, excessive NaBHCE Figure 1.
Mechanism of redox reaction.
Copyright A 2026.
ISSN 1978-2993 Bulletin of Chemical Reaction Engineering & Catalysis, 21 .
, 2026, 484 may promote rapid hydrogen evolution, particle aggregation, and surface passivation .
Ae.
Therefore, identifying an optimal NaBHCE:FeClCE stoichiometric requirement is essential for achieving efficient and controlled nZVI synthesis.
Despite the importance of this parameter, limited studies have systematically evaluated how variations in the NaBHCE:FeClCE molar ratio influence nZVI formation and its hydrogen generation performance during formic acid To address this gap, the present study investigated the effect of NaBHCE:FeClCE molar ratios ranging from 4.
4:1 to 8.
8:1 on nZVI synthesis and its hydrogen production efficiency.
The results provide new insights into the relationship between synthesis conditions and nZVI performance, supporting the development of costeffective and scalable hydrogen generation Materials and Methods 1 Materials Iron.
chloride hexahydrate (FeClCE.
6HCCO),
HCIOH, 99.
7% v/.
, and formic acid (CHCCOCC, 90% v/.
were obtained from R&M Chemicals, while sodium borohydride (NaBHCE) was supplied by Bellamy Precision.
Malaysia.
All chemicals were used as received without any further purification or modification.
Synthesis of nZVI The nZVI was synthesized via the chemical reduction of FeClCE.
6HCCO using NaBHCE as the reductant at various NaBHCE:FeClCE molar ratios ranging from 4.
4:1 to 8.
8:1, following the procedure reported by Singh et al.
The specific molarities and mass of NaBHCE and FeClCE solutions used for each ratio are summarized in Table 1.
NaBHCE solutions were prepared by dissolving the required amount .
of NaBHCE powder in 55 mL of deionized water, while FeClCE solutions were prepared by dissolving a known mass of FeClCEA 6HCCO in 12.
5 mL of an ethanol-towater mixture .
:1 v/.
Figure 2 shows the experimental setup used for nZVI synthesis.
Prior to synthesis, the entire experimental setup was purged with nitrogen gas at a flow rate of 50 mL/min for 15 minutes to remove dissolved oxygen and establish an inert atmosphere, thereby preventing premature oxidation of FeAA/FeAA species and freshly formed nZVI.
The NaBHCE solution was then added dropwise to the FeClCE solution under vigorous stirring at room temperature .
, while maintaining a continuous nitrogen flow.
The appearance of a black precipitate indicated the formation of nZVI .
After 10 minutes of reaction, the precipitated nanoparticles were thoroughly with ethanol to remove residual ions and byproducts .
The purified nZVI was then stored as suspension in ethanol to prevent oxidation .
Each nZVI suspension was subsequently freeze-dried to obtain a dry powder prior to use in hydrogen generation experiments.
Hydrogen Generation Experiments Figure 2.
Experimental setup for nZVI synthesis.
Hydrogen generation experiments were conducted in a closed, three-neck round-bottom flask serving as the reaction vessel, as illustrated in Figure 3.
The central neck was fitted with a rubber septum for the introduction of nZVI powder and injection of formic acid .
% v/.
via One of the side necks was connected through rubber tubing to an inverted, water-filled burette for hydrogen gas collection by water displacement, while the other side neck was connected to a nitrogen gas line to establish an Table 1.
Molarities of NaBHCE and FeClCE solutions used at different NaBHCE:FeClCE molar ratios.
Molar ratio NaBHCE FeClCE Number of moles NaBHCE FeClCE Molarity .
ol/L) NaBHCE FeClCE Copyright A 2026.
ISSN 1978-2993 Mass .
NaBHCE FeClCE Bulletin of Chemical Reaction Engineering & Catalysis, 21 .
, 2026, 485 inert atmosphere within the reactor.
Prior to each experiment, the reaction vessel was purged with high purity nitrogen gas .
99%) at a flow rate of 50 mL.
min-1 for 15 minutes to remove dissolved oxygen and establish an inert atmosphere.
After purging, the nitrogen line was sealed with a clamp to preserve the inert environment throughout the The gas collection system was allowed to stabilize until the burette water level remained constant, and no gas displacement was observed before the initiation of the reaction.
Gas evolution commenced only upon contact between nZVI and formic acid, indicating that the collected gas originated exclusively from the reaction.
Therefore, contamination from external nitrogen or atmospheric gases was considered negligible.
The use of a sealed reactor configuration minimized gas leakage and ensured accurate quantification of the evolved hydrogen.
All tubing, joints, and seals were inspected prior to each run to maintain airtight operation.
Hydrogen generation was first tested using nZVI synthesized at a NaBH4:FeCl3 molar ratio of 4:1, followed by experiments employing ratios of 5:1, 6.
6:1, 7.
7:1, and 8.
8:1 to assess the effect of synthesis ratio on hydrogen volume.
In each run, 25 g of nZVI powder was introduced into the reactor, followed by the injection of 10 mL of 50% v/v formic acid.
The reaction initiated immediately upon contact between nZVI and formic acid.
All experiments were conducted at room temperature .
AC) and maintained for 30 Each test was performed in triplicate, and the relative standard deviation of hydrogen volume among replicates was less than 5%.
The composition of the evolved gas was then verified using Gas Chromatography equipped with Thermal Conductivity Detector (GCAeTCD) analysis with nitrogen gas as a carrier gas to ascertain the hydrogen concentration in the gas Results and Discussion Effect of NaBHCE:FeClCE Molar Ratio on nZVI Formation UVAeVis spectroscopy was employed to assess the formation of nZVI synthesized at varying NaBHCE:FeClCE molar ratios .
4:1, 5.
5:1, 6.
6:1,
7:1, and 8.
NZVI suspensions typically exhibit a broad absorption band between 250 and 320 nm, attributed to FeAA/FeAA transitions and charge-transfer processes, which indicates successful nanoparticle formation .
shown in Figure 4, all samples displayed absorption within this region, confirming nZVI However, clear differences in Figure 4.
UVAeVis absorption spectra of nZVI synthesized at varying NaBHCE:FeClCE molar ratios .
4:1, 5.
5:1, 6.
6:1, 7.
7:1, and 8.
Figure 3.
Experimental setup for hydrogen generation from formic acid using nZVI.
Copyright A 2026.
ISSN 1978-2993 Bulletin of Chemical Reaction Engineering & Catalysis, 21 .
, 2026, 486 absorbance intensity were observed among the samples, indicating variations in nZVI yield.
The 4.
4:1 NaBH4:FeCl3 ratio produced the most intense and well-defined absorption peak, indicating the highest nZVI yield.
Increasing the NaBHCE proportion resulted in a progressive decline in absorbance intensity, indicating lower nZVI formation efficiency at higher reductant This reduction is likely due to the formation of boron-rich byproducts or borates that inhibit the complete reduction of FeAA ions and interfere with nanoparticle formation .
Excess NaBHCE can also promote rapid nucleation and uncontrolled particle growth, leading to aggregation and surface passivation .
,12,19,28Ae.
At higher molar ratios (Ou7.
, broader and weaker absorption peaks were observed.
These features distribution and increased surface oxidation, both of which reduce spectral intensity and definition.
Previous studies have reported similar Song et al.
, found that lower NaBHCE concentrations produced more reactive nZVI for trichloroethylene reduction, while Yuvakkumar et .
and Hwang et al.
observed that excessive reductant concentrations enhanced nucleation but decreased stability.
Turabik et al.
further demonstrated that both insufficient and excessive NaBHCE lead to poorly stabilized nZVI.
These findings highlight the importance of a balanced molar ratio.
Overall, the results indicate that the 4.
4:1 ratio yields the highestquality nZVI with improved stability, while higher ratios promote aggregation and surface This inverse relationship between NaBHCE concentration and nZVI yield underscores the need to optimize synthesis conditions for efficient hydrogen generation.
2 Effect of NaBHCE:FeClCE Molar Ratio on Hydrogen Generation Figure 5 shows the hydrogen volume generated from formic acid reduction using 25 g/L of nZVI synthesized at NaBHCE:FeClCE molar ratios 4:1Ae8.
8:1 after 30 minutes at room temperature with 50% .
formic acid, with the relative standard deviation of hydrogen volume among replicates was less than 5%.
A clear decreasing trend in hydrogen volume was observed as the NaBHCE:FeClCE ratio increased.
The highest hydrogen volume .
mL) was achieved at the 4.
4:1 ratio.
In contrast, only 53 mL was produced at the 8.
8:1 ratio.
This significant decline suggests that excessive NaBHCE adversely affects nZVI reactivity.
The reduced hydrogen generation at higher molar ratios may be attributed to several factors, including boron-rich byproduct formation, passivation, which collectively decrease the redox activity of nZVI .
This decline is consistent with the UVAeVis results discussed in Section 3.
indicating that excess NaBHCE reduces the formation of reactive nZVI for hydrogen While previous studies .
Song et .
Yuvakkumar et al.
Hwang et al.
and Turabik et al.
) explored nZVI synthesis and particle behavior under various reducing conditions, they did not systematically evaluated the combined influence of reductant-to-precursor In contrast, the present study directly correlates synthesis molar ratios with hydrogen evolution efficiency, thereby addressing this key research gap as shown in Table 2.
Overall, these findings demonstrate that maintaining a 4.
4:1 NaBHCE:FeClCE ratio is essential not only for optimizing nanoparticle formation but also for maximizing hydrogen Unlike previous reports, this study provides a systematic assessment of how synthesis molar ratios govern nZVI reactivity in formic acid reduction.
Future studies should focus on kinetic modeling, mechanistic analysis of nZVIAeformate interactions, and the incorporation of stabilizing support materials to minimize aggregation and enhance the reusability of nZVI, similar to other nanomaterial-based systems .
Evaluating nZVI performance in continuous or pilot-scale systems is also recommended to advance its application in sustainable hydrogen production technologies.
3 Hydrogen Purity and Gas Composition Figure 5.
Effect of NaBHCE:FeClCE molar ratio on hydrogen volume in 50% v/v formic acid over 30 min reaction time.
The evolved gas mixture was characterised by GC-TCD to determine hydrogen purity and quantify the composition of gaseous products generated from the nZVI by formic acid Table 3 shows the concentrations of the gaseous species detected in the collected As summarised in Table 3, hydrogen accounted for 99.
81 mol% of the total detected gas, indicating that the nZVI predominantly produces hydrogen with negligible interference from other gaseous species.
Only trace amounts Copyright A 2026.
ISSN 1978-2993 Bulletin of Chemical Reaction Engineering & Catalysis, 21 .
, 2026, 487 of COCC .
14 mol%) and CO .
05 mol%) were detected, confirming minimal side reactions following correction for the blank response.
This level of hydrogen purity is consistent with prior results from nZVI-based hydrogen production For instance, hydrogen produced from a nZVI dissolution system was reported to contain minimal levels of common gaseous impurities such as COCC and CHCE, indicating that nZVI itself can serve as a direct source of hydrogen in biomass-based systems .
Compared to previous findings, the present system has a high hydrogen purity, showing that the nZVI can produce high-purity hydrogen with little gaseous byproducts, highlighting their potential for clean and sustainable energy applications.
Conclusions This study systematically investigated the effect of NaBHCE:FeClCE molar ratios on the synthesis of nZVI and its performance in hydrogen generation via formic acid reduction.
UVAeVis spectroscopy revealed that the NaBH4:FeCl3 molar ratio significantly influenced nZVI formation, with the 4.
4:1 ratio producing the highest absorbance intensity and thus the most effective nZVI formation.
Increasing the NaBH4 proportion led to a gradual decline in absorbance, likely due to the formation of excess boron-rich byproducts that promoted particle agglomeration and surface passivation, thereby reducing the amount of reactive nZVI formed.
These effects were consistent with the hydrogen generation results, where nZVI synthesized at the 4.
4:1 ratio yielded the highest hydrogen volume .
mL).
Higher NaBH4:FeCl3 ratios significantly reduced hydrogen output, confirming that precursor molar ratios critically determine the redox activity and reactivity of nZVI in the formic acid reduction Overall.
Table 2.
Comparison table of relevant literature alongside the present study.
Material nZV -formic acid nZVI formic acid 1 g uncoated ferrobots in 2 mL aqueous FA .
Ae100%), gas collected after 1 min nZVI formic acid nZVI weak acid Formic acid decomposition, varying nZVI dosage .
Ae1000 g/L), temperature .
Ae 75AC), reaction time .
Ae 30 mi.
Microsize FeA or scrap iron with NaHCOCE and citric acid under mild anaerobic conditions nZVI Ascorbic acid nZVI No.
Reaction conditions Formic acid reduction, closed reactor with water displacement Photo fermentation of bean dregs and corn stover, initial pH 9 Synthesis of ZVI particles with varying FeAA.
NaBHCE, stabilizer, temperature, pH, and stirring rates Hydrogen generation Max HCC: 98 mL at 4.
4:1.
decreases to 53 mL at 8.
HCC volume increases with FA concentration .
75 mL at 50Ae60 vol%) and ferrobot mass.
highest at 2 min reaction Max HCC: 215 mL at 800 g/L nZVI, 25AC, 30 min.
area decrease after reaction correlates with lower HCC Molar ratio Yes.
NaBHCE:FeClCE enhances nZVI formation and HCC generation Not studied Ref.
This .
Not studied .
HCC production rate: 0.
09Ae 55 g(HCC)/kg(FeA)Ah.
>85
vol% HCC after 1 day and >94 vol% HCC at end of each negligible HCC without Max HCC: 767.
5 A 2.
8 mL Not studied .
Not studied .
Not studied Yes.
size influenced by synthesis .
Table 3.
Concentration of gases collected from formic acid reduction with nZVI.
Total gas concentration (% mol.
HCC Gas concentration (% mol.
COCC Copyright A 2026.
ISSN 1978-2993 Bulletin of Chemical Reaction Engineering & Catalysis, 21 .
, 2026, 488 NaBHCE:FeClCE ratio was found to be optimal for balancing nanoparticle formation, stability, and hydrogen volume.
These findings provide valuable insights for designing cost-effective and scalable formic acid-based hydrogen production systems using nZVI.
Chang.
Jampang.
Green extraction of gold.
and copper(II) from chloride media by palm kernel fatty acid Journal of Water Process Engineering.
DOI: 10.
1016/j.
Halim.
Chang.
Morad.
Extraction of Cu(II) ions from aqueous solutions by free fatty acid-rich oils as green extractants.
Journal of Water Process Engineering, 33.
DOI:
1016/j.
Eppinger.
Huang.
Formic Acid as a Hydrogen Energy Carrier.
ACS Energy Lett.
188Ae195.
DOI:
1021/acsenergylett.
Wang.
Meng.
Gao.
Jin.
Ge.
Liu, .
Xing.
Recent progress in hydrogen production from formic acid decomposition.
Int.
Hydrogen Energy, 43, 7055Ae7071.
DOI:
1016/j.
Singh.
Singh.
Kumar.
Hydrogen energy future with formic acid: A renewable chemical hydrogen storage system.
Catal.
Sci.
Technol.
12Ae40.
DOI:
1039/c5cy01276g .
Singh.
Rarotra.
Pasumarthi.
Mandal.
Bandyopadhyay.
Formic acid powered reusable autonomous ferrobots for efficient hydrogen generation under ambient conditions.
Journal of Materials Chemistry 6.
, 9209Ae9219.
DOI:
1039/c8ta02205d.
Jamei.
Khosravi.
Anvaripour.
A novel ultrasound assisted method in synthesis of NZVI particles.
Ultrasonics Sonochemistry, 21.
, 226Ae233.
DOI:
1016/j.
Zhang.
Tang.
Yan.
Liang.
Liu.
Yang.
Green-synthesized, biocharsupported nZVI from mango kernel residue for Performance, mechanism and regeneration.
Chinese Journal of Chemical Engineering, 71, 91Ae101.
DOI: 10.
1016/j.
Sathish.
Masih.
Gupta.
Kumar.
Raja.
Singh.
Al-Enizi.
Pandit.
Gupta.
Senthilkumar.
Yusuf.
Sustainable nanoparticles of Non-Zero-valent iron .
ZVI) production from various biological Journal of King Saud University Science, 36.
DOI:
1016/j.
Bounab.
Duclaux.
Reinert.
Oumedjbeur.
Boukhalfa.
Penhoud.
Muller.
Improvement of zero valent iron nanoparticles by ultrasound-assisted synthesis, study of Cr(VI) removal and application for the treatment of metal surface Journal Environmental Chemical Engineering, 9.
DOI: 10.
1016/j.
Acknowledgment The authors gratefully acknowledge the Ministry of Higher Education (MOHE).
Malaysia, for financial support through the Fundamental Research
Grant
Scheme
(FRGS/1/2022/TK08/UITM/02/5
FRGS/1/2023/TK08/UITM/02/.
and Universiti Teknologi MARA (UiTM) via the UiTM Conference Support Fund.
Special thanks to Universiti Sains Malaysia (USM).
Nibong Tebal, for access to key instruments.
CRedit Author Statement Author Contributions:
Yusuf:
Conceptualization.
Methodology.
Investigation.
Writing Original Draft.
Writing.
Review and Editing.
Visualization.
Zubair:
Resources.
Supervision Halim:
Supervision.
Funding acquisition .
Chang:
Conceptualization.
Validation.
Writing.
Review and Editing.
Supervision.
Funding acquisition.
All authors have read and agreed to the published version of the manuscript.
References