Jongwoo Lim1,2,Juwon Kim1,Si Young Lee3,Se-Jun Kim4,Bonho Koo1,Namdong Kim5,Matthew Markus6,David Shapiro6,Shu-Chih Haw2,Daan Hein Alsem7,Norman Salmon7,Hyungjun Kim4,Yun Jeong Hwang1
Seoul National University1,National Synchrotron Radiation Research Center2,University of Michigan–Ann Arbor3,Korea Advanced Institute of Science and Technology4,Pohang Light Source5,Advanced Light Source6,Hummingbird Sceintific7
Jongwoo Lim1,2,Juwon Kim1,Si Young Lee3,Se-Jun Kim4,Bonho Koo1,Namdong Kim5,Matthew Markus6,David Shapiro6,Shu-Chih Haw2,Daan Hein Alsem7,Norman Salmon7,Hyungjun Kim4,Yun Jeong Hwang1
Seoul National University1,National Synchrotron Radiation Research Center2,University of Michigan–Ann Arbor3,Korea Advanced Institute of Science and Technology4,Pohang Light Source5,Advanced Light Source6,Hummingbird Sceintific7
Unraveling and guiding the dynamic evolution of active species in efficient electrochemical CO2 reduction (ECR) catalysts remains a challenge. Through observing the chemical and morphological changes of high-performance ECR catalysts in action, we pinpointed the essential intermediate species that lead to highly active surfaces and notably improved C–C coupling activity. Operando scanning transmission soft X-ray microscopy, a method that illustrates the nanoscale chemical composition distribution of Cu-based catalysts during ECR, showed that the emergence of partial Cu+ phases and surface Cu2+ phases are key to the dynamic dissolution-redeposition mechanism and heightened C–C coupling activity, respectively. We further established that this dissolution-redeposition process is electrochemical formation Cu<sup>2+</sup> phases, even at elevated cathodic potentials. Our correlative microscopy and electrochemical analysis strengthen the substantial contribution of Cu2+ phases toward C-C coupling. In addition, DFT calculations corroborated that Cu2+ phases amplifies C–C coupling activity.