As a vital process for solar fuel synthesis, water oxidation remains a challenging reaction to perform using durable and cost-effective systems. Despite decades of intense research, our understanding of the detailed processes involved is still limited, particularly under photochemical conditions. Recent research has shown that the overall kinetics of water oxidation by a molecular dyad depends on the coordination between photocharge generation and the subsequent chemical steps. This work explores similar effects of heterogeneous solar water oxidation systems. By varying a key variable, the reaction temperature, we discovered distinctly different behaviors on two model systems, TiO2 and Fe2O3. TiO2 exhibited a monotonically increasing water oxidation performance with rising temperature across the entire applied potential range, between 0.1 and 1.5 V vs the reversible hydrogen electrode (RHE). In contrast, Fe2O3 showed increased performance with increasing temperature at high applied potentials (>1.2 V vs RHE) but decreased performance at low applied potentials (<1.2 V vs RHE). This decrease in performance with temperature on Fe2O3 was attributed to an increased level of electron–hole recombination, as confirmed by intensity-modulated photocurrent spectroscopy (IMPS). The origin of the differing temperature dependences on TiO2 and Fe2O3 was further ascribed to their different surface chemical kinetics. These results highlight the chemical nature of charge recombination in photoelectrochemical (PEC) systems, where surface electrons recombine with holes stored in surface chemical species. They also indicate that PEC kinetics are not constrained by a single rate-determining chemical step, highlighting the importance of an integrated approach to studying such systems. Moreover, the results suggest that for practical solar water splitting devices higher temperatures are not always beneficial for reaction rates, especially under low driving force conditions.

Tianying Liu

Pan Wang

Wei Li

David Z. Wang

Damith D. Lekamge

Boqiang Chen

Frances A. Houle

Matthias M. Waegele

Dunwei Wang

ACS Central Science

ACS CENTRAL SCIENCE 发表关于化学和相关领域研究的最引人注目、最重要的主要报告，其中化学方法发挥着关键作用。它也是美国化学学会出版的第一个完全开放获取的期刊。

ACS Central Science publishes the most significant and noteworthy primary reports on research in chemistry and related fields, particularly those where chemical methods play a crucial role. It is also the first fully open access journal published by the American Chemical Society.

《ACS Central Science》发表关于化学及相关领域的最重要和最引人注目的研究报告，特别是那些化学方法发挥关键作用的研究。这是美国化学学会出版的首个完全开放获取的期刊。

Category	Quartile
化学	1
化学, 化学综合	1

Temperature-Dependent Water Oxidation Kinetics: Implications and Insights

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Journal Info

Category	Quartile
CHEMISTRY, MULTIDISCIPLINARY	1