Current Water-Splitting Catalysts

Recently, Hill and coworkers [69] have developed a homogeneous Co catalyst that self-assembles in water from inorganic salts (Co, W, and P). It employs a polytungstate polyoxometalate (POM) ligand, which is oxidatively resistant, thus enhancing 

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Photo-electrochemical (PEC) processes can produce hydrogen in one step - splitting water by illuminating a water-immersed semiconductor with sunlight. There are two types of photo-electrochemical processes. The first uses soluble metal complexes as catalysts. When these complexes dissolve, they absorb solar energy and produce an electrical charge that drives the water splitting reaction. This process mimics photo-synthesis, however, currently there is minimal experience in this process. 

Aquivion E87-12S short-side chain perfluorosulfonic acid (SSC-PFSA) membrane with equivalent weight (EW) of 870 g eq and 120 pm thickness produced by Solvay Specialty Polymers was tested in a polymer electrolyte membrane water electrolyser (PEMWE) and compared to a benchmark Nation N115 membrane (EW 1100 g eq ) of similar thickness [27]. Both membranes were tested in conjunction with in-house prepared unsupported Ir02 anode and carbon-supported Pt cathode electrocatalyst. The electrocatalysts consisted of nanosized Ir02 and Pt particles (particle size 2-4 nm). The electrochemical tests showed better water splitting performance for the Aquivion membrane and ionomer-based membrane-electrode assembly (MEA) as compared to Nafion (Fig. 2.21). Lower ohmic drop constraints and smaller polarization resistance were observed for the electrocatalyst-Aquivion ionomer interface indicating a better catalyst-electrolyte interface. A current density of 3.2 A cm for water... 

As discussed in section 5.3 (eqn (5.4) and (5.5), Table 5.1), the evolution of molecular hydrogen from water splitting and the reduction of CO2 to hydrocarbons involve the transfer of multiple electrons. In particular, light driven reduction of CO2 to methane or methanol with concomitant water oxidation, is kinetically very demanding due to the involvement of four or six proto/ electron transfers, respectively. Additionally, the one electron reduction of CO2 to C02 is thermodynamically unfavourable E°= —1.9 vs. NHE at pH 7). The development of bio-inspired reduction catalysts that lower the activation barrier and facilitate such reactions is currently being pursued by several research groups and a number of important achievements have been reported in recent years. ... 

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