In research on photocatalytic overall water splitting, verifying whether the molar ratio of the products hydrogen (H₂) and oxygen (O₂) conforms to the stoichiometric ratio of 2:1 is one of the key criteria for determining whether a true overall water-splitting cycle has been achieved[1]. However, in practical experiments, many researchers find that the measured O₂ values often deviate from theoretical expectations, and oxygen signals can even be detected in blank experiments without any catalyst. Are these excess oxygen signals indicative of real catalytic activity, or merely “scientific illusions” caused by system errors?
Theoretical Analysis: “Amplified” Measurement Errors
In the calculation of the apparent quantum yield (AQY), the accuracy of oxygen data directly determines the validity of the conclusions. The commonly used formula for AQY is as follows:
Here, n represents the number of product molecules, Nₚ is the number of incident photons, and K is the number of transferred electrons. In water splitting, the hydrogen evolution reaction (HER) is a two-electron process (K = 2), whereas the oxygen evolution reaction (OER) involves four-electron transfer (K = 4)[2]. This means that, in AQY calculations, the amount of oxygen must be multiplied by 4 for electron conversion, making its measurement highly influential on the final AQY value. Any deviation in oxygen detection will therefore be significantly amplified in the final results.
Currently, contamination in O₂ data mainly arises from two aspects:
The atmosphere contains approximately 21% oxygen.Kazunari Domen’s research group emphasized in a 2024 publication that due to the extremely high background level of environmental oxygen, it is extremely difficult to distinguish between oxygen generated from the reaction and that introduced through air leakage[1]. If the system has a leakage rate on the order of 0.2 μmol/h, the accumulated error over long-duration experiments can severely interfere with accurate interpretation of catalytic mechanisms[3].
A study published in 《ACS Energy Letters》 explored the identification and elimination of false-positive results[4]. The research indicates that false-positive signals in experiments may originate from multiple sources, such as redox side reactions of sacrificial agents or even slight decomposition of the catalyst itself. If the baseline noise from system airtightness is not well characterized, researchers cannot reliably distinguish the true catalytic activity from mixed signals.
If you are still using outdated equipment with poor airtightness, the “high efficiency” you take pride in may simply be an experimental illusion accumulated from a leakage rate of 0.2 μmol/h over 10 hours.
To quantify the real impact of airtightness on experimental outcomes, PerfectLight conducted comparative tests on 6A and μGAS1001.
Under conditions without illumination and without catalysts, the baseline drift curves of oxygen leakage rates were obtained. As shown in the figure, μGAS1001 demonstrates a cleaner baseline noise:
Within the same 4-hour testing window, the cumulative baseline drift of 6A was 0.988 μmol, while μGAS1001-1# and μGAS1001-2# showed 0.372 μmol and 0.348 μmol, respectively. Compared to 6A, μGAS1001 reduces cumulative baseline drift by approximately 62.3% and 64.8%, indicating superior airtightness and baseline stability. For trace oxygen evolution or quantum efficiency calculations, such differences directly impact baseline determination and result reliability.
Based on the experimental report, μGAS1001 shows outstanding performance in both airtightness and stability:
μGAS1001 is not merely an incremental model update, but a structural redesign centered on the concept of “data consistency”:
• Patented Sampling Valve Manifold: Optimizes the sampling pathway and switching process, ensuring more stable sampling and reducing fluctuations that interfere with oxygen data.
• High-Speed Magnetically Coupled Internal Circulation: Enables “zero-pulsation” output through magnetic coupling, enhancing gas circulation and mixing within the reactor. This allows generated oxygen to enter the detection system faster and more uniformly, improving data accuracy and stability.
From laboratory validation to industrial-scale production, every step forward in photochemical technology is essentially a pursuit of certainty.
On the path toward high-performance photocatalytic materials, precise characterization accounts for half of the success.μGAS1001 Micro Gas Reaction Evaluation System eliminates background oxygen interference through a next-generation architectural redesign.
The PerfectLight upgrade subsidy program is now officially launched:
For all research groups using Labsolar-6A/IIIAG (and similar photocatalytic systems), PerfectLight offers substantial subsidies:
Use your existing equipment as qualification (any brand accepted) and upgrade to the new-generation μGAS1001.
This program ensures “zero downtime” delivery—new equipment is installed before the old one is removed, ensuring uninterrupted experiments.
The first batch includes 50 units, with 45 remaining.→Click here for more details →!
[1] Takata, T., Hisatomi, T., Domen, K., et al. "Best Practices for Assessing Performance of Photocatalytic Water Splitting Systems," Advanced Materials, 2024, 36, 2406848.
[2] Nishioka, S., Osterloh, F. E., et al. "Photocatalytic water splitting," Nature Reviews Methods Primers, 2023, 3, 42.
[3] Hisatomi, T., Domen, K. "Best practices for photocatalytic water splitting," Nature Sustainability, 2024, 7(9), 1082-1084.
[4] Zhang, Y., Yao, D., Xia, B., Jaroniec, M., Ran, J., Qiao, S. Z. "Photocatalytic CO₂ Reduction: Identification and Elimination of False-Positive Results," ACS Energy Letters, 2022, 7, 1441-1447.
