Abstract: In  electrochemical  energy  conversion  and  storage  (EECS)  technologies, 

developing highly  active  electrocatalysts and  electrode  materials  with  improved 

electrochemical and cycling activities has been a crucial study for many decades. The metal 

oxyhydroxides  (MOOHs)  are  robust  materials  searching for  new  nanostructured 

catalysts/electrodes with enhanced electrochemical performance and desired structural and 

composite characteristics. Their recent advances in defect engineering are very inspiring. 

Herein, we discuss the advantages and present the accomplishments of various MOOHs (M = 

mono-, bi-, and mixed-metal) in EECS systems, including supercapacitors, alkali metal ion 

batteries,  and  hydrogen  and  oxygen  evolutions  via  water  electrolysis.  We  thoroughly 

discussed the design and synthetic strategies of MOOH with the control of distinct promises 

for  EECS.  Additionally,  we  highlighted  useful  accessibilities  to  unravel  practical  and 

scientific  interpretations in  targeting  MOOH  products  for  EECS.  Finally,  we  concisely 

proposed the existing difficulties and directions for future consideration.