Electrocatalysts in the last 30 years – from precious metals to cheaper but sophisticated complex systems

The paper is concerned with the advance and diversification of materials used as electrodes for evolution of chlorine, hydrogen and oxygen. In the first part a survey is given of our research in the field of electrocatalysis 30 years ago, when Ru and other precious metals were the exclusive electrocatalyst materials. A brief scope of the achievements of electrocatalysis in that period is given as well. The second part deals with our recent research on formulation and characterization of a new class of electrocatalysts, based on a combination of non-precious metals, but still exhibiting an ability to promote hydrogen evolution reaction as successful as platinum and other precious metals are. Among the produced (non-platinum) catalysts the best performance for the hydrogen evolution reaction was measured at the electrocatalyst containing Co or CoNi as hyper d phase and TiO2 as hypo d phase. A typical formulation of the electrodes is, e.g.: 18% (TiO2) alloyed with 10% Co and applied on a substrat of carbon powder (Vulcan XC-72). At this electrocatalyst hydrogen evolution overpotential at 10 mA·cm–2 was 40 mV higher than that on a corresponding electrode containing platinum as hyper d phase. For both electrocatalyst systems of interest analysis is made and aimed to recognize the sources that cause the electrocatalytic activity. This is the proper way how to use the acquired knowledge for further improvement of the existing materials or/and to discover new ones. Key words: electrocatalysis; hydrogen evolution; hypo-hyper d-electrocatalyst