Irfan clocked 1:20:21 in the race participated by 56 walkers, bettering the old national record of 1:20.35 in the name of Gurmeet Singh.
Gurmeet finished 33rd with a timing of 1:23:34 while the third Indian in the fray, Baljinder Singh was 43rd in 1:25:39.
Irfan did not begin well as he was 27th after the 6-km mark but went ahead at fifth after the 8-km distance. He could not maintain his place after that though he hung on to the leading pack for a while.
Irfan improved upon his earlier personal best of 1:22:09 which he recorded in the IAAF World Race Walking Cup in Russia in May.
All the three Indians had qualified for the Olympics after achieving 'A' qualification standard.
Ding Chen of China won the gold in Olympic record timing of 1:18:46 while the silver and bronze went to Erick Barrondo (1:18:57) of Guatemala and Zhen Wang (1:19:25) of China.