With the 5th Gerischer Symposium on Photoelectrochemical Energy Conversion, this symposium series has returned to the main field of Heinz Gerischer′s work. More than 50 years after Gerischer′s early seminal contributions, we witness a renaissance of the field that is fuelled by the search for alternative energy generation in a time when atmospheric poisoning is not negligible anymore. Indicators for the renewed interest in photoelectrochemical energy conversion are, among other activities, the establishment of a solar fuel hub (the Joint Center for Artificial Photosynthesis) in California, the founding of several solar-fuel-related Energy Frontier Research Centers in the USA, the founding of a Solar Fuel Institute at the Helmholtz Center Berlin and the instalment of a Priority Program of the Deutsche Forschungsgemeinschaft on photoelectrocatalysis.
The response by the international community was overwhelming and we had to select the most suited contributions because of limited space for poster presentations and for oral contributions. We were additionally lucky that virtually all renowned international experts were positively responding to our invitation, giving the meeting the character of an intense high-level scientific exchange. The symposium topics were chosen according to the relevant developments in the field of solar fuels and of photovoltaic energy conversion at the semiconductor–electrolyte phase boundary. These topics, for example, Charge Transfer, General Photoelectrochemistry, Interfaces, Materials, Photoelectrochemistry: Catalysis, Photoelectrochemistry: Photovoltaics, and Bioinspired Systems reflect the breadth of the present approaches. They also show the necessity and challenge for multi-disciplinary research, which is one of the fascinating characteristics of photoelectrochemistry.
Besides the success of the meeting, much work, some of it very fundamental, still remains to be done. The Marcus–Gerischer theory, as an example, only describes single-electron outer-sphere charge-transfer processes whereas many of the processes related with photoelectrochemical energy conversion are multi-electron-transfer reactions, some of them with inner-sphere character. Both water splitting reactions, anodic and cathodic, are multi-electron processes. Light-induced carbon dioxide reduction to hydrocarbons is characterized by an initial step that must be circumvented, possibly by an accumulative electron-transfer reaction. The factors that define (photo)electrocatalytic activity have not yet been fully assessed and in photoelectrode development, combinatorial approaches and educated guess strategies are employed for the preparation of earth-abundant absorbers and electrocatalysts.
Many participants travelled large distances to be able to contribute to this rather short meeting and I would like to express a special gratitude to Prof. A. Fujishima, who took time off as president of Tokyo University to be able to participate in the symposium. From his seminal work 40 years ago until today, he remains dedicated to our science despite so many other duties. I also express special thanks to Prof. Gerhard Ertl who was the guest of honour of this conference.
Sadly, the organization of this Gerischer Symposium was the last major international activity of Prof. Dieter M. Kolb, who at the time of the meeting, was already seriously ill. I believe that many colleagues noted that he thoroughly enjoyed the meeting and only a few even noticed his disease. The worldwide scientific community and this symposium issue suffer the loss of Dieter M. Kolb who passed away on October 4, 2011. He leaves behind a legacy of beautiful science and innovations, part of it is mentioned in the obituary in this issue.