Non-noble metal-based bifunctional electrocatalysts for hydrogen production

Hydrogen is a promising candidate for clean and sustainable energy resources to substitute fossil fuels to mitigate global environmental issues. Electrochemical hydrogen production has been regarded as a viable and promising strategy. The overall water splitting is currently the predominant electrochemical hydrogen production method, which could be driven by renewable energy to achieve sustainable production. However, the current challenges are the intrinsically sluggish and energy-intensive oxygen evolution reduction (OER) at the anode and the expensive noble metal-based catalysts for overall water splitting, which limit the practical applications. Extensive efforts have been made to develop bifunctional non-noble metal-based electrocatalysts to boost hydrogen production efficiency and lower the cost. Meanwhile, alternative oxidation reactions with faster kinetics and less energy requirement than OER are being explored as the anodic reaction to couple with the hydrogen evolution reaction for energy-saving hydrogen production. In this review, the non-noble metal-based bifunctional electrocatalysts for overall water splitting, as well as other novel energy-saving hydrogen productions have been introduced and summarized. Current challenges and outlooks are commented on at the end of the article.