Water Oxidation Catalysts: The Quest for New Oxide-Based Materials

Abstract

The expected shortage of fossil fuels as well as the accompanying climate change are among the major challenges of the 21st century. A global shift to a sustainable energy landscape is, therefore, of utmost importance. Over the past few years, solar technologies have entered the energy market and have paved the way to replace fossil-based energy sources, in the long term. In particular, electrochemical solar-to-hydrogen technologies have attracted a lot of interest—not only in academia, but also in industry. Solar water splitting (artificial photosynthesis) is one of the most active areas in contemporary materials and catalysis research. The development of low-cost, efficient, and stable water oxidation catalysts (WOCs) remains crucial for artificial photosynthesis applications, because WOCs still represent a major economical and efficient bottleneck. In the following, we summarize recent advances in water oxidation catalysts development, with selected examples from 2016 onwards. This condensed survey demonstrates that the ongoing quest for new materials and informed catalyst design is a dynamic and rapidly developing research area.

Immobilization of Co, Mn, Ni and Fe oxide co-catalysts on TiO2 for photocatalytic water splitting reactions

“…In the case of the NiO x -TiO 2 composite, we observed no apparent increase in OER rate compared to bare TiO 2 , despite the fact that NiOthat is present in our compositeand various Ni oxyhydroxides are known for their excellent water oxidation performance. 64,65 However, it has also been reported, that performance of Ni-based co-catalysts is strongly dependent on the calcination conditions and may need to be optimized to obtain desired OER rates. Nevertheless, the as-prepared NiO x -TiO 2 composite containing both metallic Ni and NiO can be considered as a promising candidate for overall water splitting as it contains both HER and OER sites whose initial ratio can be controlled during the synthesis.…”

Molecular and heterogenized dinuclear Ir-Cp* water oxidation catalysts bearing EDTA or EDTMP as bridging and anchoring ligands

“…This has caused an explosion of interest for developing efficient water oxidation catalysts (WOCs) [3][4][5][6][7][8]. A large variety of homogeneous [9][10][11][12][13][14][15][16][17], heterogenized [18][19][20][21][22][23][24], and heterogeneous [25][26][27][28][29][30][31][32] WOCs has been proposed but, despite the enormous advances, their performance is not technologically satisfactory, yet [33]. Scheme 1 (Color online) Sketch of the step-wise extraction of protons and electrons from water, leading to benign O2, "orchestrated" by a suitable transition metal complex ([M]), having several accessible oxidation states (n = oxidation state of the metal).…”

Ir- and Ru-doped layered double hydroxides as affordable heterogeneous catalysts for electrochemical water oxidation

“…This is the reason why water oxidation (WO) has become one of the most studied reactions, over the last decades, especially as far as the development of a catalyst (C) for its acceleration is concerned. [1][2][3][4][5][6] Significant, but still technologically unsatisfactory, 7 results have been achieved by using homogeneous, [8][9][10][11][12][13][14][15][16][17] heterogenized, [18][19][20][21][22][23][24]25 and heterogeneous [26][27][28][29][30][31][32][33] WOCs. The best performances are usually obtained by using noble-metal (e.g.…”