Electrical conversion of water and carbon dioxide into chemical fuels provides a promising approach to store massive renewable energy. In this talk, the catalyst design and in-situ investigation for water and carbon dioxide electrolysis will be presented. 3d transition metal oxide/non-oxides were developed as the high-efficient electrocatalysts for water electrolysis. The in-situ XAS and XRD were employed to study the detailed catalytic mechanisms. On the other hand, the synthesized single-atom catalysts exhibit high catalytic performance toward carbon dioxide electrolysis. The in-situ XAS identified the single-atom nature of the catalysts and the catalytic process. The catalytic environment for carbon dioxide electrolysis was also found to affect the catalytic activities significantly, included in this talk.