Hydrogenating process and magnetocaloric effect in La0.7Pr0.3Fe11.5Si1.5C0.2Hx hydrides

► We prepared the interstitial La0.7Pr0.3Fe11.5Si1.5C0.2Hx hydrides with large magnetocaloric effect. ► It is found that introducing carbon atoms into La0.7Pr0.3Fe11.5Si1.5 compound can lower the rate of hydrogen absorption/release, which is beneficial for an accurate control of hydrogen content. ► A large magnetic entropy change of −22.1 J/kg K without hysteresis loss for La0.7Pr0.3Fe11.5Si1.5C0.2H1.2 is observed at room temperature for a field change of 0-5 T.