Toward Standardized Photocatalytic Oxygen Evolution Rates Using RuO2@TiO2 as a Benchmark

Abstract

Summary Quantitative comparison of photocatalytic performances across different photocatalysis setups is technically challenging. Here, we combine the concepts of relative and optimal photonic efficiencies to normalize activities with an internal benchmark material, RuO 2 photodeposited on a P25-TiO 2 photocatalyst, which was optimized for reproducibility of the oxygen evolution reaction (OER). Additionally, a general set of good practices was identified to ensure reliable quantification of photocatalytic OER, including photoreactor design, photocatalyst dispersion, and control of parasitic reactions caused by the sacrificial electron acceptor. Moreover, a method combining optical modeling and measurements was proposed to quantify the benchmark absorbed and scattered light (7.6% and 81.2%, respectively, of λ = 300–500 nm incident photons), rather than just incident light (≈AM 1.5G), to estimate its internal quantum efficiency (16%). We advocate the adoption of the instrumental and theoretical framework provided here to facilitate material standardization and comparison in the field of artificial photosynthesis.

An All‐Organic D‐A System for Visible‐Light‐Driven Overall Water Splitting

“…The two types of O 2 species ( 16‐18 O 2 and 18‐18 O 2 ) further affirm that the oxygen source of O 2 is indeed derived from H 2 O caused by photocatalytic overall water splitting. [ 55,56 ]…”

Organic materials as photocatalysts for water splitting

“…This goes in hand with the standardisation of measurements that will be of importance to guide the field towards more efficient overall water splitting systems. 110,111 Solar-to-hydrogen efficiencies using solar simulator light sources have to be reported with the measurement conditions that were used (e.g. pressure, catalysts concentration, set-up type).…”

Irradiance-Controlled Photoassisted Synthesis of Sub-Nanometre Sized Ruthenium Nanoparticles as Co-Catalyst for TiO2 in Photocatalytic Reactions

“…On the other hand, the differences observed between the samples with similar particle size suggest a significant influence of the latter parameter, which is the sample with the highest ratio of Ru δ+ species giving rise to the highest activity. In this respect, as it was stressed in the introduction, RuO x particles are generally found as good oxidation catalysts, while rather metallic species tend to promote reduction reactions [7,30], due to their different band alignment with respect to TiO 2 [31,32]. Further investigations are underway in order to discriminate between those effects, as well as to study the extension of this research to reduction-intensive reactions (e.g., photocatalytic hydrogen evolution or photocatalytic CO 2 reduction) in order to explore the implications of the control of size and oxidation state of the nanoparticles in the optimisation of oxidation/reduction reactions.…”

“…Materials 2021, 14, 4799 4 of 10 previous results using RuCl3 as precursor [7]. The apparent contradiction between the similar Ru contents and the different absorbance at 325 nm after each synthesis reveals that some Ru species remain in the solution, even if not detected by UV-vis spectroscopy in the used wavelength interval, and that the disappearance of the Ru(III) species absorbing at 325 nm does not directly mean that Ru is deposited as a solid on the surface of titania, further suggesting that the reduction of Ru(III) is only one of several steps in the photodeposition process, as mentioned in the previous paragraph.…”

“…Although the oxidative photoassisted synthesis of metal oxide nanoparticles is scarcer, the cases of PbO 2 and RuO 2 can be mentioned [5]. Ruthenium is actually a promising metal to be used as a (co)catalyst in both metallic and oxidized states not only in photocatalytic reduction and oxidation reactions, respectively [6,7], but also in other catalytic reactions such as those taking place in the conversion of biomass into fuels and value-added chemicals [8] or in electrochemical devices such as batteries [9], supercapacitors [10], electrolyzers [11] or fuel cells [12]. The photoassisted synthesis of ruthenium nanoparticles on semiconductor surfaces, however, has been considerably less studied than for other metals.…”